The clinical content of preconception care: nutrition and dietary supplements
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The clinical content of preconception care: nutrition
and dietary supplements
Paula M. Gardiner, MD, MPH; Lauren Nelson; Cynthia S. Shellhaas, MD, MPH; Anne L. Dunlop, MD;
Richard Long, MD; Sara Andrist, MPH, RD, LD; Brian W. Jack, MD
A t the time of conception, maternal
nutritional status is an important
determinant of embryonic and fetal
Women of child-bearing age should achieve and maintain good nutritional status prior
to conception to help minimize health risks to both mothers and infants. Many women
growth.1 Placental and fetal growth is may not be aware of the importance of preconception nutrition and supplementation or
most vulnerable to maternal nutrition have access to nutrition information. Health care providers should be knowledgeable
status during the preimplantation pe- about preconception/pregnancy-related nutrition and take the initiative to discuss this
riod and the period of rapid placental de- information during preconception counseling. Women of reproductive age should be
velopment, which occurs during the first counseled to consume a well-balanced diet including fruits and vegetables, iron and
few weeks of development typically be- calcium-rich foods, and protein-containing foods as well as 400 g of folic acid daily.
fore pregnancy has been confirmed.2 More research is critically needed on the efficacy and safety of dietary supplements and
Most organs form 3-7 weeks after the last the role of obesity in birth outcomes. Preconception counseling is the perfect opportunity
menstrual period and any teratogenic ef- for the health care provider to discuss a healthy eating guideline, dietary supplement
fects may occur by this time.3 Evidence is intake, and maintaining a healthy weight status.
emerging that a mother’s diet and life-
Key words: folic acid, health risks, pregnancy-related nutrition, reproductive-age
style influence the long-term health of
women
her children.2,4 Recent research suggests
that inadequate levels of maternal nutri-
ents during the crucial period of fetal de-
velopment may lead to reprogramming the infant to chronic illnesses in adult- ● Nutrition monitoring, evaluation,
within the fetal tissues that predisposes hood.5 A woman’s nutritional status is and referrals to dietitians occur as
influenced by numerous variables in- needed, depending on the individu-
cluding genetics, environment, lifestyle al’s needs.7,8
From the Department of Family Medicine, habits, the presence of disease or physio- In this manuscript, we review the evi-
Boston University School of Medicine,
logical stressors, and drug-toxicant dence for safety and efficacy of nutrition,
Boston, MA (Drs Gardiner, Long, and Jack
exposures.6 dietary supplements, and maternal
and Ms Nelson); Department of Family and
Preventive Medicine, Emory University Nutritional assessment and recom- weight during the preconception period.
School of Medicine, Atlanta, GA (Dr mendations are important components
Dunlop); Division of Maternal and Fetal of preconception counseling. The key Dietary intake prior to conception
Medicine, Department of Obstetrics and components of the nutrition care pro- Background: The quality of a woman’s
Gynecology, The Ohio State University cess include: diet during pregnancy has an influence
College of Medicine, Columbus, OH (Dr on positive fetal and maternal outcomes;
Shellhaas); and Nutrition Section, Georgia ● A nutrition assessment, including
analysis and interpretation of anthro- therefore, a healthy, balanced diet is im-
Division of Public Health, Atlanta, GA (Dr
Andrist). pometric data and adequacy and qual- portant before as well as during pregnan-
ity of dietary habits (including dietary cy.1,9 Many women of child-bearing age
Received June 17, 2008; revised Oct. 16,
2008; accepted Oct. 17, 2008. supplements). in the United States do not maintain a
Reprints: Paula Gardiner, MD, MPH, Boston ● A nutrition diagnosis, which will iden- healthy diet prior to, during, and after
Medical Center, 1 Boston Medical Center tify and label any nutrition-related pregnancy. Not all women have financial
Place, Dowling 5 South, Boston, MA 02118. problems or risk factors such as obe- or logistical access to a high-quality
paula.gardiner@bmc.org.
sity or eating disorders. diet.10 Furthermore, several studies have
Conflict of Interest: Paula M. Gardiner, MD, shown that most women of reproductive
MPH; Lauren Nelson; Cynthia S. Shellhaas,
● The nutrition intervention, at which
MD, MPH; Anne L. Dunlop, MD; Richard Long, time the individual’s dietary goals and age are not getting enough vitamins A, C,
MD; Sara Andrist, MPH, RD, LD; and Brian W. plan of action are established and care B6, and E, folic acid, calcium, iron, zinc,
Jack, MD have no conflict of interest including is delivered with the emphasis on ap- and magnesium in their diet.11-13 This
grants, honoraria, advisory board membership, propriate weight gain, consumption of underscores the importance of encour-
or share holdings.
a variety of foods according to the Di- aging healthy eating behaviors early in a
0002-9378/$34.00 woman’s child-bearing years because
etary Guidelines 2005, appropriate di-
© 2008 Mosby, Inc. All rights reserved.
doi: 10.1016/j.ajog.2008.10.049 etary supplement use, and physical ac- improving dietary habits requires long-
tivity. term effort.
Supplement to DECEMBER 2008 American Journal of Obstetrics & Gynecology S345Supplement www.AJOG.org
Clinical studies have shown a positive This difference in regulation may influ- fant demands (genetic and environmen-
association between a healthy diet dur- ence the quality of products on the mar- tal), sensitivity, and selectivity of
ing the preconception period and preg- ket, and our knowledge of dietary sup- measured outcomes and proper use of
nancy and improved birth out- plement safety and efficacy prior to proxy measures.38
comes.14,15 For example, a case-control conception and during perinatal period. Recommendation. All women of re-
study on the risk of orofacial clefts by There exist serious concerns about di- productive age should be asked about
Krapels et al16 concluded that the pre- etary supplement safety and efficacy, their use of dietary supplements (vita-
conception energy-adjusted intake of quality control, misidentification, adul- mins, minerals, traditional/home reme-
vegetable protein, fiber, beta-carotene, teration, contamination, adverse events, dies, herbal products, weight loss prod-
vitamin C, vitamin E, iron, and magne- and interactions with medications.23 ucts, etc) as part of preconception care
sium were all significantly lower in cases Various national surveys estimate that plan and should be advised about what is
compared with controls. Additionally, 18-52% of the US population use dietary or is not known about their impact,
there have been a number of reviews writ- supplements and women use more sup- safety, and efficacy. Strength of recom-
ten on the importance of a healthy diet plements then men.24-26 Many women mendation: C; quality of evidence: III.
prior to and during pregnancy.7,10,17-19 use multivitamins, single vitamins,
In 1992, the Institute of Medicine (IOM) herbal products, traditional medicines, Vitamin A
published Nutrition during Pregnancy folk remedies, weight loss or sport sup- Background: Vitamin A is a fat-soluble
and Lactation: An Implementation plements, and other dietary supplements vitamin found in several forms. Vitamin
Guide.20 The IOM has also published a prior to and during pregnancy.27-29 Un- A found in foods that come from animals
series of reports establishing the dietary fortunately, many women do not discuss (liver, whole milk) is called preformed
reference intakes (DRIs).21 Throughout their dietary supplement use with their vitamin A. It is absorbed in the form of
this review, we will state the DRI for each health care professionals.30,31 It is critical retinol, which is made into retinal and
supplement we discuss. that all health care professionals ask their retinoic acid (other active forms of vita-
Finally, the US Department of Agri- patients which vitamins, minerals, min A) in the body. Vitamin A that is
culture’s (USDA) Food Guide Pyramid herbs, traditional remedies, and other found in fruits and vegetables is called
and Dietary Guidelines for Americans dietary supplements they are using. provitamin A carotenoid, which is made
have resources for patients to consume Women should be encouraged to bring into retinol in the body. There is also a
foods that meet the nutritional require- in the labels or bottles of all dietary sup- synthetic analog (13-cis retinoic acid)
ments of pregnancy.22 USDA has re- plements (pills, powders, teas, etc) to de- isotretinoin (Accutane; Roche Pharma-
leased the MyPyramid food guidance termine whether excessive levels of spe- ceuticals, Nutley, NJ), a medication used
system, which includes MyPyramid Plan cific nutrients (or other bioactive to treat severe, cystic acne, and related
for Moms, which helps women identify compounds) are being consumed on a dermatoses. Adequate vitamin A is es-
the appropriate food plan according to daily basis.8,32 sential for proper visual functioning, fe-
pregnancy status, age, weight and tal growth, reproduction, immunity,
height, and physical activity level (www. Evidence for efficacy: Although many and epithelial tissue integrity.39 Because
mypyramid.gov/mypyramidmoms). health care professionals do recommend vitamin A is lipid soluble, it crosses the
MyPyramid identifies an appropriate certain dietary supplements prior to, placenta easily and has a long half-life.
food plan that covers the individual’s en- during, and after pregnancy (eg, folate, Although normal fetal development re-
ergy needs and dietary reference intakes iron, and calcium), the safety and effi- quires sufficient vitamin A intake, very
in the perinatal period.1,7 cacy of many dietary supplements (eg, high levels of preformed vitamin A (reti-
sport supplements and weight loss prod- noic acid) supplementation has been as-
Dietary supplements ucts) have not been well established. For sociated with miscarriage and birth de-
Background: Although many of our re- example, there are few clinical trials eval- fects that affect the central nervous
quired vitamins, minerals, amino acids, uating the safety and efficacy prior to and system and craniofacial, cardiovascular,
essential fatty acids, and other constitu- during pregnancy on herbal prod- and thymus development.39
ents are found in food, the physiologic ucts.33-35 Today much data available on Currently the recommended dietary
demands of the woman during precon- herbal products are based on case re- allowance of preformed vitamin A for
ception and pregnancy may require ad- ports, animal studies, and retrospective women is 700 retinol activity equivalents
ditional dietary supplementation. Re- studies.36,37 Because of the high preva- (RAEs) per day, with a tolerable upper
quirements for folic acid, calcium, iron, lence of dietary supplement use among intake level of 3000 RAEs/day or 10,000
zinc, vitamin D, vitamin C, and vitamin women, more research on the safety and IU/day.40 Dietary sources of vitamin A
B increase substantially during preg- efficacy of dietary supplements prior to and beta-carotene (leafy vegetables, car-
nancy.22 In the United States, dietary and during pregnancy is urgently rots, eggs, and diary products) do not
supplements are regulated differently needed. Future studies should focus on pose a risk of excessive intakes and
than prescription medications by the subject characteristics that may influ- should be included in a healthy diet. Vi-
Food and Drug Administration (FDA). ence our ability to meet maternal and in- tamin A from beta-carotene is not
S346 American Journal of Obstetrics & Gynecology Supplement to DECEMBER 2008www.AJOG.org Supplement
known to increase the risk of birth Folic acid observational and randomized controlled
defects.41 Background: Folic acid, a water-soluble studies culminate in an estimate that at
B-complex vitamin required for de- least 70% of NTDs could be prevented if
Evidence of efficacy: During pregnancy, oxyribonucleic acid synthesis and cell di- the embryo were exposed to protective
evidence in humans suggests that more vision, is a nutrient currently recognized amounts of folic acid during the critical
than 10,000 IU of vitamin A per day may as important prior to and during preg- window of organogenesis.52,64-66
be teratogenic, resulting in cranial/neu- nancy because of its proven preventive
ral crest defects.42 However, other stud- Current recommendations: The US Pub-
properties against neural tube defects
ies have shown that periconceptional vi- lic Health Service, American Academy of
(NTDs).52 Neural tube defects are seri-
tamin A exposures greater than 10,000 Pediatrics, American Dietetic Associa-
ous birth defects of the spine (spina bi-
IU/day were not associated with in- tion, American College of Obstetricians
fida) and brain (anencephaly). NTDs af-
creased risk for cranial neural crest de- and Gynecologists (ACOG), and Ameri-
fect approximately 3000 pregnancies
fects or neural tube defects.43 Although can Academy of Family Medicine rec-
each year in the United States and are the
ommend that women consume 400 g
animal data clearly show that high dose second most common major congenital
of folic acid daily.7,67-69 The USDA rec-
vitamin A is teratogenic, such data are anomaly worldwide.53 Populations at in-
ommends women of child-bearing age
difficult to obtain in humans as human creased risk for NTDs or folic acid defi-
who may become pregnant and those in
clinical trails are not ethically possible.41 ciency include Hispanic women, obese
the first trimester of pregnancy consume
Vitamin A also appears to be protec- women, diabetic women with poor gly- adequate synthetic folic acid daily (from
tive in pregnant women with human im- cemic control, women with prior NTDs, fortified foods or supplements) in addi-
munodeficiency virus/acquired immu- and women with seizure disorder taking tion to food forms of folate from a varied
nodeficiency syndrome.44-47 There is antiepileptic medications.12,54,55 diet.70
growing evidence from clinical trials in Folate levels can be increased by con- Recommendation. All women of re-
developing countries that vitamin A may suming folate-rich foods or ingesting fo- productive age should be advised to in-
protect against maternal morbidity, al- lic acid, a synthetic compound available gest 0.4 mg (400 g) of synthetic folic
though more research is needed.44,48-50 through dietary supplements and acid daily, obtained from fortified foods
through fortified foods. The major di- and/or supplements. In addition, all
Current recommendations: A World etary sources of naturally occurring fo- women should be advised to consume a
Health Organization expert group late are legumes, green leafy vegetables, balanced, healthy diet, which includes
consultation concluded that daily citrus fruits and juices, and breads and folate-rich foods. Strength of recommen-
doses of up to 10,000 IU (equivalent to cereals that contained folic enriched dation: A; quality of evidence: I-a.
3000 g retinol) or weekly 25,000 IU flour. Folic acid is approximately 1.7
(7500 RAEs) are probably safe, espe- times more bioavailable than folate and Multivitamins
cially in areas in which vitamin A defi- therefore has a greater efficiency in im- Background: Multivitamins are typically
ciency is thought to be common51 The pacting folate levels.56 Supplementing the most commonly used dietary supple-
half-life of the main metabolite of reti- dietary intake with folic acid has been ments reported in surveys in the United
noic acid is 50 hours, so most of the recommended by many professional or- States.71,72 Willett and Stamfer73 con-
drug and biotransformation products ganizations because of the difficulty for cluded that there is greater benefit than
are gone within 10 days of the last dose. woman to obtain the extra folate re- harm in recommending a daily multivi-
Etretinate and isotretinoin (Accu- quired periconceptionally through the tamin that does not exceed the daily rec-
tane), synthetic derivatives of retinol, diet alone. The current recommended ommended intake of its component vi-
are known to cause serious birth de- daily intake (RDI) for folic acid is 400 g tamins for most adults. In their review,
fects and should not be taken during for women of preconception age and 600 Willett and Stamfer73 noted that a mul-
pregnancy or if there is a possibility of g during pregnancy.57 The recom- tivitamin is especially important for
becoming pregnant. The current rec- mended dose is higher (4000 g) for women who might become pregnant,
ommendation is to discontinue such women who have had a infant with an persons who regularly consume 1 or 2
medications such as at least 1 month NTD.58 Numerous studies have reported alcoholic drinks per day, those who tend
prior to attempting pregnancy. that women in the United States do not to absorb vitamin B12 poorly, vegans,
Recommendation. Currently the rec- consume the recommended 400 g of and those with limited resources to af-
ommended dietary allowance of pre- folic acid.59-61 Furthermore, inadequate ford adequate fruits and vegetables.
folate levels have been linked to in-
formed vitamin A for women is 700 Evidence of efficacy: There is substantial
creased risks of stroke, cancer, and
RAEs per day, with a tolerable upper in- evidence showing that taking multivita-
dementia.62,63
take level for pregnancy is 3000 RAEs/ mins with at least 400 g of folic acid
day or 10,000 IU/day; Strength of recom- Evidence of efficacy: There is clear scien- daily may also reduce the incidence of
mendation: B; quality of evidence for tific evidence that folic acid protects other malformations such as orofacial
toxicity: III. against neural tube defects. Numerous cleft, limb deficiencies, cardiac defects,
Supplement to DECEMBER 2008 American Journal of Obstetrics & Gynecology S347Supplement www.AJOG.org
urinary tract defects, and omphalo- breakfast cereals. Other dietary sources ogists recommend daily consumption of
cele.74-80 A recent metaanalysis of 41 tri- include fatty fish (salmon, mackerel, 400-800 IU.96 In the United States, the cur-
als reported that multivitamin supple- tuna, sardine), egg yolks, beef liver, and rent DRI is 200 IU/day with 200 IU/day in
ments provide consistent protection cheese. pregnancy. The USDA guidelines note that
against neural tube defects, cardiovascu- Vitamin D is essential for the health of people with dark skin and people exposed
lar defects, limb defects, and other birth pregnant women and their infants. Cur- to insufficient ultraviolet band radiation
defects.74 In this metaanalysis, both case rently there is an increasing prevalence (ie, sunlight) consume extra vitamin D
control studies (odds ratio [OR], 0.76; of vitamin D insufficiency and deficiency from vitamin D-fortified foods and/or
95% confidence interval [CI], 0.62-0.93) in pregnant women and infants in the supplements.22
and cohort and randomized controlled United States and internationally.82-87 Recommendation. The evidence is in-
studies (OR, 0.42; 95% CI, 0.06-2.84) Vitamin D deficiency is common among sufficient to recommend for or against
showed lower incidence of cleft palate pregnant women in ethic minority routine screening or vitamin D supple-
when women took mulitvitamins. groups.88 Vitamin D deficiency during mentation during preconception coun-
For oral cleft with or without cleft pregnancy is reflected in lower maternal seling. Based on the emerging data of the
palate, case control studies (OR, 0.63; weight gain; biochemical evidence of dis- importance of vitamin D for women and
95% CI, 0.54-0.73) and cohort and turbed skeletal homeostasis in the infant; infants; however, clinicians should be
randomized controlled studies (OR, and in extreme situations, reduced bone
0.58; 95% CI, 0.28-1.19) followed the aware of the risk factors for vitamin D
mineralization, radiologically evident deficiency. Additionally, for women
same pattern. For urinary tract anom- rickets, and fractures.89,90 Additionally,
alies and congenital hydrocephalus, with vitamin D deficiency, education on
vitamin D insufficiency has also been as- vitamin D in the diet and supplementa-
only the case controls studies showed a sociated in some studies with other
statistically significant decrease in tion should be a part of preconception
health outcomes that affect women, in-
anomalies. Finally, for congenital hy- care. Currently we do not have data for
cluding asthma, diabetes, autoimmune
drocephalus there was an OR of 0.37 the optimal dose prior to and during
diseases, and certain cancers.83,91-93
(95% CI, 0.24-0.56) in case control pregnancy. More data are urgently
Women at risk for vitamin D defi-
studies and 1.54 (95% CI, 0.53-4.50) needed. Strength of recommendation: B;
ciency include women who are not ex-
for cohort studies, and randomized quality of evidence: I b.
posed to enough sunlight; whose dietary
controlled studies.74 Although multi-
vitamin D intake is low (no dairy or
ple micronutrient supplementation is Calcium
lactose intolerant); who wear head
theoretically preferable to supplemen- Background: Calcium is essential for
coverings.
tation with iron and folic acid alone, bone development and health and main-
especially in developing countries in Evidence of efficacy: The optimal dose of tenance throughout life and in preg-
which multiple deficiencies are preva- vitamin D for the preconception period nancy, yet many women in the United
lent, more data need to be collected to and during pregnancy is unknown. Obser- States do not consume the recom-
determine the advantages of different vational studies and vitamin D supple- mended amount of calcium prior to and
multiple micronutrient formulations mentation trials among pregnant women during pregnancy.97-99 During preg-
for pregnant and lactating women.81 at high risk of vitamin D deficiency showed nancy, the growing fetus receives its total
Recommendation. All women of re- improved neonatal handling of calcium nourishment from maternal sources.
productive age should be encouraged to with improved maternal vitamin D status. The dynamic balance between skeletal
take a folic acid– containing multivita- Results concerning the effects of vitamin D calcium storage and fetal nutritional
min supplement for the purpose of sup- on maternal weight gain and fetal growth needs can affect the maternal calcium
porting healthy pregnancy outcomes in these high-risk populations are conflict- equilibrium adversely. Therefore, if ade-
and preventing congenital anomalies. ing and inconclusive.94,95 Despite taking quate bone has not been built before
Strength of recommendation: A; quality of prenatal vitamins, vitamin D deficiency
evidence: II2. pregnancy and adequate calcium is not
has been demonstrated in pregnant wom- part of the maternal diet, bone can be
en.83 Most experts agree that the current degraded as calcium is taken from the
Vitamin D DRI of 200-400 IU is too low and that
Background: Vitamin D is a lipid-solu- maternal skeleton.100 When completing
based on current evidence, daily require-
ble vitamin important in the metabolism a diet history during preconception
ments may be closer to 1000 IU or higher
of calcium and phosphorus. It promotes counseling, it is important to ask about
and that more research is needed on the
calcium absorption and bone mineral- dietary calcium consumption (milk, for-
optimal vitamin D dose and blood
ization. It may be obtained from either tified orange juice, etc), calcium supple-
concentrations for several health
endogenous production from sun expo- mentation, and use of antacids to assess
outcomes.83
sure or dietary sources. The major di- the woman’s overall calcium intake. Vi-
etary sources are fortified items, particu- Current recommendations: The Ameri- tamin D intake is necessary to facilitate
larly milk, orange juice, and some can College of Obstetricians and Gynecol- calcium absorption.
S348 American Journal of Obstetrics & Gynecology Supplement to DECEMBER 2008www.AJOG.org Supplement
Evidence of Efficacy: Studies indicate that mia in the United States is significant serum iron and ferritin levels and serum
increases in calcium intake during preg- among vulnerable populations. For ex- and red cell folate levels. Supplementa-
nancy improve maternal bone health of ample, the National Health and Nutri- tion resulted in a substantial reduction of
mother and neonate. Higher birthweight tion Examination Survey 1999-2000 re- women with a hemoglobin level below
babies, a reduced risk of preterm deliv- ported iron deficiency prevalence among 10 or 10.5 g in late pregnancy.
ery, and lower infant blood pressure women aged 12-49 years was 9-16%. A more recent prospective study done
have all been linked with a high calcium Among minority females in the same age by Ronnenberg et al116 in 2004 examined
intake during pregnancy.100,101 More re- group, the prevalence of iron deficiency the relation between preconception he-
search is needed to assess the optimal was approximately 3 times higher than moglobin concentration and pregnancy
does of calcium prior to and during the Healthy People 2010 objective outcomes in 405 healthy Chinese women
pregnancy.100,102-106 A 2008 metaanaly- of 5%.109 who were planning pregnancy. This
sis of 12 good-quality clinical trials re- Reproductive-aged women are at risk study showed an association between
ported that the risk of high blood pres- of iron deficiency because of blood loss preconception maternal anemia status
sure was reduced with calcium from menstruation, poor diet, and fre- and adverse pregnancy outcomes. The
supplementation rather than placebo quent pregnancies.110 In a study of fertile odds of low birthweight and fetal growth
(11 trials, 14,946 women: relative risk women, only 20% had iron reserves of restriction were 6.5 and 4.6 times higher,
(RR), 0.70; 95% CI, 0.57-0.86). There greater than 500 mg, 40% had iron stores respectively, in women with moderate
was also a reduction in the risk of pre- of 100-500 mg, and 40% had virtually no anemia (hemoglobin ⬍ 95 g/L) compared
eclampsia associated with calcium sup- iron stores.111 Potential fetal complica- with nonanemic controls. Anemia attrib-
plementation (12 trials, 15,206 women: tions secondary to anemia include spon- uted to iron deficiency was significantly as-
RR, 0.48; 95% CI, 0.33-0.69). There was taneous prematurity and intrauterine sociated with decreased birthweight.
no overall effect on the risk of preterm growth restriction.112 The mecha- A recent randomized controlled trial
birth or stillbirth or death before dis- nism(s) by which this occurs are not of 867 pregnant women (less than 20
charge from the hospital.107 Many re- clear. Prior to conception and during weeks) was assigned randomly to receive
views have concluded that the lack of pregnancy, women should eat iron-rich prenatal supplements with 30 mg of iron
available evidence restricts the ability to foods (lean meat, poultry, and iron for- as ferrous sulfate or placebo until 26-29
form strong conclusions, especially with tified cereals). Foods that inhibit iron ab- weeks of gestation. The mean birth-
respect to supplementation’s effect on sorption, such as whole-grain cereals, weight was higher by 108 g (P ⫽ .03), and
maternal bone health during pregnancy. unleavened whole-grain breads, le- the incidence of preterm delivery was
More research is needed to assess the op- gumes, tea, and coffee, should be con- lower (8% vs 14%; P ⫽ .05) in the 30 mg
timal does of calcium prior to and during sumed separately from iron-fortified group compared with the control group.
pregnancy.100,102-106 foods. The Centers for Disease Control Iron supplementation did not affect the
and Prevention (CDC) recommends 18 prevalence of small-for-gestational-age
Current recommendations: The Institute
mg/day for women and 27 mg/day for all infants or third-trimester iron status.117
of Medicine currently recommends 1000
pregnant women113 In another recent clinical trial, 513
mg/day of calcium for pregnant and lac-
low-income pregnant women were ran-
tating women who are 19-50 years old Evidence of efficacy: There are several
domly assigned to receive a monthly
and 1300 mg/day for pregnant and lac- systematic reviews reporting the benefits
supply of ferrous sulfate or placebo until
tating women who are younger than 19 of iron combined with folate prior to and
28 weeks of gestation. Compared with
years old.108 during pregnancy. The Cochrane collab-
placebo, iron supplementation from en-
Recommendation. Women of repro- oration completed a systematic review
rollment to 28 weeks of gestation did not
ductive age should be counseled about on 20 randomized controlled trials of
significantly affect the overall prevalence
the importance of achieving the recom- iron supplementation in pregnancy with
of anemia or the incidence of preterm
mended calcium intake level through normal hemoglobin levels (⬎ 10 dL) at
births but led to a significantly higher
diet or supplementation. Calcium less than 28 weeks of gestation.114 Iron
mean birthweight (P ⫽ .010), a signifi-
supplements should be recommended if supplementation raised or maintained
cantly lower incidence of low-birth-
dietary sources are inadequate. Strength the serum ferritin level above 10 mg/L
weight infants (P ⫽ .003), and a signifi-
of recommendation: A; quality of evidence: and reduced the number of women with
cantly lower incidence of preterm low-
I b. low hemoglobin levels late in pregnancy.
birthweight infants (P ⫽ .017).118
The reviewers concluded that iron sup-
Additional studies on the effectiveness of
Iron plementation had no detectable effect
preconception iron supplementation on
Background: Iron deficiency is the most on any substantive measures of either
preventing prenatal iron depletion are
common nutritional deficiency world- maternal or fetal outcomes.114 One re-
needed.119
wide and is the most common cause of view looked at 8 trials involving 5449
anemia in pregnancy. The prevalence of women.115 Routine supplementation Current recommendations: The CDC is-
iron deficiency and iron deficiency ane- with iron or folate raised or maintained sued guidelines in 1998 for preventing
Supplement to DECEMBER 2008 American Journal of Obstetrics & Gynecology S349Supplement www.AJOG.org
iron deficiency based on age and sex. women of child-bearing age to avoid weight was slightly greater in infants
They state that for girls aged 12-18 years consuming swordfish, king mackerel, born to women in the fish oil group
and nonpregnant women of child-bear- shark, and tilefish. The warnings also compared with controls. However,
ing age, iron status screening should oc- recommend that those groups eat no there were no overall differences be-
cur every 5-10 years during a routine more than 12 ounces of fish weekly and tween the groups in the proportion of
examination. Annual iron screening no more than 6 ounces of canned alba- low birthweight or small-for-gesta-
should be conducted for women with ex- core tuna weekly.123 Concerns have been tional-age babies.133
isting risk factors for iron deficiency. If raised that eating oil-rich fish exposes the
anemia is confirmed with a second test, a Current recommendations: There are
fetus to dioxins and polychlorinated bi-
trial of oral iron is warranted. Other several recommendations and guidelines
phenyls, which are environmental
sources recommend confirmation of about omega fatty acid consumption for
pollutants.
iron deficiency as a cause of the anemia women. The Institute of Medicine set
Several studies have shown an associ-
prior to initiation of therapy.120 The adequate intake for linoleic acid (N-6) 3
ation between maternal dietary intake of
American College of Obstetricians and g/day for pregnant women and 12 g/day
oily fish or oils providing n-3 EFA during
Gynecologists recommend all pregnant for women 18-50 years old. The ade-
pregnancy and visual and cognitive de-
women should be screened for anemia quate intake for ␣-N-3 is 1.4 g/day for
velopment, maturity of sleep patterns,
pregnant women and 1.1 g/day for
and those with iron deficiency anemia and motor activity in infants.124-127
should be treated with supplemental women 18-50 years old, respectively.134
Whether all woman should be supple-
iron, in addition to prenatal vitamins.110 The USDA recommends to keep total fat
mented and at what dose of EFAs (eg,
The USDA food guidelines recommend intake between 20-35% of calories, with
fish or fish oil supplements during pre-
that women of child-bearing age who most fats coming from sources of poly-
conception and pregnancy) has been the
may become pregnant eat foods high in unsaturated and monounsaturated fatty
subject of much debate and recent
hemeiron and/or consume iron-rich acids, such as fish, nuts, and vegetable
research3
plant foods or iron-fortified foods with oils.70
an enhancer of iron absorption, such as Evidence of efficacy: There is mixed evi- The International Society for the
vitamin C–rich foods22 dence for the efficacy of essential fatty Study of Fatty Acids and Lipids recom-
Recommendation. At a preconception acids such as fish oil against adverse mends adequate intakes of 4.44 g of lino-
visit, screening should be conducted for pregnancy outcomes for mother and leic acid and 2.22 g of ␣-N-6, with 0.22 g
women with risk factors for iron defi- child during preconception and preg- or more of DHA and 0.22 g of EFA for
ciency for the purposes of identifying nancy.128,129 For example, epidemiolog- adults and 0.3 g or more of DHA daily for
and treating anemia. There is evidence to ical evidence suggests an association be- pregnant women.135 The Perinatal Lipid
recommend that all women should be tween fish intake and birthweight. Intake Working Group recently released
screened at a preconception visit for iron Another study showed a positive corre- guidelines for maternal dietary fat intake
deficiency anemia for the purpose of im- lation with low fish consumption in early in Europe. After reviewing the literature,
proving perinatal outcomes. Strength of pregnancy and increased risk for pre- they report that intakes of up to 1 g/d
recommendation: A; quality of evidence: term delivery and low birthweight.130 A DHA or 2 䡠 7 g/day n-3 long-chain poly-
IB. metaanalysis of 6 randomized controlled unsaturated fatty acids have been used in
trials demonstrated that supplementa- randomized clinical trials without signif-
Essential fatty acids tion with omega-3 fatty acids was associ- icant adverse effects. These guidelines
Background: The essential fatty acids ated with a significantly greater length of recommend that pregnant and lactating
(EFA) linoleic and alpha-linolenic acid, pregnancy than in control subjects; how- women should aim to achieve an average
and their long-chain derivatives arachi- ever, there was no evidence that sup- dietary intake of at least 200 mg of DHA
donic acid and docosahexaenoic acid plementation influenced the percent- per day. The guidelines note that women
(DHA) are important structural compo- age of preterm deliveries, the rate of of child-bearing age should aim to con-
nents of cell membranes, the central ner- low-birthweight infants, or the rate of sume 1-2 portions of sea fish per week,
vous system, and retinal cell membrane preeclampsia.131 including oily fish.136
structure.121,122 EFAs cannot be synthe- In a review, the results of several ran- Recommendation. During the precon-
sized in the body and must be ingested by domized clinical studies have indicated ception period, women should be en-
food. Essential fatty acids are found in that supplementation with fish oils may couraged to eat a diet rich in EFAs in-
such foods as oily fish, flax seeds, wal- lead to modest increases in gestation cluding omega 3 and omega 6 fatty acids.
nuts, and vegetables oils. length, birthweight, or both.132 The Co- To achieve this, women should be ad-
In 2005, the FDA and Environmental chrane collaboration review of 6 clinical vised to consume at least 12 ounces of
Protection Agency, because of high mer- trials found women randomized to a fish fish weekly and no more than 6 ounces of
cury levels detected in fish, issued warn- oil supplement had a mean gestation that canned albacore tuna weekly. More re-
ings that advise young children, preg- was 2.6 days longer than women allo- search is critically needed to asses the
nant women, nursing women, and cated to placebo or no treatment. Birth- risks and benefits of fish and fish oil con-
S350 American Journal of Obstetrics & Gynecology Supplement to DECEMBER 2008www.AJOG.org Supplement
sumption during the preconception pe- nonpregnant adults, 220 g for pregnant overweight in young adults predicts sub-
riod. Strength of recommendation: B; women, and 290 g for lactating wom- sequent obesity.144,147 Weight retained
quality of evidence: I-b. en.139 The World Health Organization, from previous gestations is an impor-
United Nations Children’s Fund, and the tant contributor to higher-than-opti-
Iodine International Council for Control of Io- mal BMIs in child-bearing women.
Background: Worldwide iodine defi- dine Deficiency Disorders recommend
ciency is the single most important pre- daily iodine intake of 150 g for adults Evidence of efficacy: Counseling to sup-
ventable cause of brain damage. In 2005 (ⱖ 12 years of age) and 200 g for preg- port improvements in diet and physical
the World Health Organization esti- nant and lactating women.140 activity are considered first-line inter-
mated 2 billion people, 35% of the world Recommendation. Women of repro- ventions.147 In a systematic evidence re-
population were iodine deficient.137 Io- ductive age with iodine deficiency view, the US Preventive Services Task
dine is necessary for the production of should be counseled on the risks of this Force concluded that counseling alone
thyroid hormones, thyroxine, and tri- condition to pregnancy outcomes and or with pharmacotherapy can promote
iodothyronine, and it must be provided the importance of maintaining adequate modest sustained weight loss.144,147 The
in the diet. Inadequate iodine intake daily dietary iodine intake of 150 g dur- most successful nonsurgical approaches
leads to inadequate thyroid hormone ing preconception and at least 200 g to weight loss were intensive, weight-fo-
production and to a spectrum of disor- when pregnant or lactating. Public cused counseling consisting of more
ders, iodine deficiency disorders, includ- health efforts to implement salt iodiza- than 1 session per month or multicom-
ing abortion, stillbirth, mental retarda- tion programs should be encouraged for ponent, intensive interventions that
tion, cretinism, increased neonatal and all women residing in regions with en- combine nutrition and exercise counsel-
infant mortality, goiter, and hypothy- demic iodine deficiency. Strength of recom- ing with supportive, skill-building be-
roidism. Iodine is readily transferred to mendation: A; quality of evidence: II-2. havior interventions. Evidence from
the fetus, and the fetal thyroid concen- randomized controlled trials of long-
trates iodine and synthesizes thyroid Preconception weight term improved health with weight loss is
hormones by 10-12 weeks’ gestation. Io- and body mass index limited.
dine deficiency in pregnancy negatively Overweight Interventions about gestational weight
affects the normal maturation of the de- Background: Approximately one third from randomized controlled trials in
veloping fetal central nervous system, of all women in the United States are pregnant obese women have mixed re-
particularly myelination, and is respon- obese, and obesity is identified as the sults. In a review by Guelinckx et al148,
sible for cognitive impairment, perma- fastest-growing health problem in the only 2 of 7 trials, using nutrition and
nent mental retardation, and in its most country.141 Obesity, defined as a body physical activity as an intervention,
severe form, cretinism.138 mass index (BMI) of 30 kg/m2 or greater, reached a significant decrease in gesta-
Iodine deficiency disorders are among is associated with elevated risks of type 2 tional weight gain. There is a growing
the easiest and least costly of all disorders diabetes; hypertension; infertility; heart literature of clinical trials on the safety
to prevent. Adding a small amount of io- disease; gallbladder disease; immobility; and perinatal outcomes for women
dine in the form of potassium iodate or osteoarthritis; sleep apnea; respiratory who have undergone gastric bypass
potassium iodide to dietary salt is effec- impairment; social stigmatization; and a surgery.149-155
tive for prevention. Salt iodization is the variety of cancers, including breast, uter- ACOG suggests that utilizing the
recommended, preferred strategy to ine, and colon.142-145 Adverse perinatal stages of change model as adapted for
control and eliminate iodine deficiency. outcomes associated with maternal obe- overweight and obesity may help deter-
Sufficient dietary iodine throughout the sity include neural tube defects, preterm mine patient motivation and interest in
life cycle, especially during the precon- delivery, stillbirth, gestational diabetes, weight loss. ACOG recommends setting
ception period, can minimize the risk of hypertensive and thromboembolic dis- an initial goal of losing 5-10% of total
iodine deficiency during critical, early fe- orders, macrosomia, low Apgar scores, body weight over a 6 month period as
tal development. Studies of the impact of postpartum anemia, cesarean delivery, realistic and achievable.147 Weight loss is
iodine supplementation specifically be- and shoulder dystocia.142,143 Further- not recommended during any preg-
fore pregnancy have not been done. more, women who are obese before con- nancy, irrespective of pregravid weight.
Identification and treatment of iodine ception tend to gain and retain more Therefore, to minimize the risks of obe-
deficiency disorders before pregnancy is weight during pregnancy.146 sity on reproductive outcomes, interven-
an effective preventive public health The risks associated with high BMIs tions must occur before pregnancy.
strategy. are best addressed before conception be-
cause weight loss during pregnancy is Current recommendations: In an ACOG
Current recommendations: The Institute not recommended. Health risks are bet- Committee Opinion on obesity issued in
of Medicine’s Food and Nutrition Board ter established for obese persons than for October 2005, the following recommen-
recommend minimum daily intake of overweight individuals (BMI 25-29.9 kg/ dations were made: (1) BMI should be
iodine in the United States of 150 g for m2). However, even mild to moderate calculated for all women and (2) appro-
Supplement to DECEMBER 2008 American Journal of Obstetrics & Gynecology S351Supplement www.AJOG.org
priate interventions or referrals to pro- ciencies, heart irregularities, osteoporo- conceiving, but they may experience sig-
mote a healthy weight and lifestyle sis, amenorrhea, and infertility. For nificant difficulty during the pregnancy
should be offered.147 Relative to non- women who become pregnant, low pre- related to binge eating, purging, and lax-
pregnant populations, the US Preventive gravid weight is associated with in- ative or diuretic use.162
Services Task Force found that counsel- creased risks for preterm birth and low Women with eating disorders may be
ing and pharmacotherapy can promote birthweight, which are all major contrib- reluctant to disclose symptoms, and
modest sustained weight loss and that utors to poor pregnancy outcomes.157-160 there are no reliable laboratory indica-
pharmacoptherapy appears to be safe in tors for eating disorders, so clinicians
the short term; however, long-term Evidence of efficacy: A low prepregnancy need to be aware of warning signs and
safety has not been established. The task BMI may also increase the risk of birth use effective assessment techniques.163
force also noted that, in selected patients, defects such as gastroschisis. A study by Assessment should be done for condi-
surgery promotes large amounts of Lam et al161 found that infants born to tions such as bulimia and anorexia; once
weight loss with rare but potentially se- underweight mothers (prepregnancy identified, nutritional counseling and in
vere complications.144 BMI ⬍ 18.1 kg/m2) were more than 3 some cases treatment of an underlying
In 1990, the IOM published a report times as likely to have gastroschisis com- emotional condition should be initiated.
that reevaluated the evidence regarding pared with infants of normal-weight A multidisciplinary approach is most ef-
optimal weight gain during pregnancy. mothers (prepregnancy BMI 18.1-28.3 fective in treating a woman with an eat-
The report concluded that prepregnancy kg/m2). In this study, every unit increase ing disorder in pregnancy.163,164
body weight should be taken into ac- in BMI was estimated to decrease the risk Recommendation. All women of re-
count when advising on optimal weight for gastroschisis by about 11%. productive age with anorexia and bu-
gain. For women with a normal prepreg- Weight gain in pregnancy cannot limia should be counseled about the risks
nancy BMI, a weight gain of around 0.4 overcome the risks associated with a low to fertility and future pregnancies and
kg/week during the second and third tri- pregravid weight. Therefore, women should be encouraged to enter into treat-
mesters is recommended. For under- should be counseled during the precon- ment programs before pregnancy.
weight women, a weight gain of 0.5 kg/ ceptional period on the potential risks of Strength of recommendation: A; quality of
week is the target, whereas for their weight on fertility and on preg- evidence: III.
overweight women, 0.3 kg/week is nancy outcome.
recommended156 Recommendation. All women should Conclusion
Recommendation. All women should have their BMI calculated at least annu- Good nutrition is an essential compo-
have their BMI calculated at least annu- ally. All women of reproductive age with nent of attaining a healthy pregnancy
ally. All women of reproductive age with a BMI 18.5 kg/m2 or less should be coun- and birth outcome. Women of repro-
a BMI of 25 kg/m2 or greater should be seled about the short- and long-term ductive age should be advised that the
counseled about the risks to their own risks to their own health and the risks to quality of a woman’s diet may influence
health, the additional risk associated future pregnancies, including infertility. her pregnancy outcomes. Women of re-
with exceeding the overweight category, All women with a low BMI should be as- productive age, especially those who are
and the risks to future pregnancies, in- sessed for eating disorders and distor- planning a pregnancy, should be coun-
cluding infertility. All women with a tions of body image. Strength of recom- seled to consume a well-balanced diet in-
BMI of 25 kg/m2 or greater should be mendation: A; quality of evidence: III. cluding fruits and vegetables, calcium-
offered specific strategies improve the rich foods, and protein-containing foods
balance and quality of the diet, decrease Eating disorders daily and increase their consumption of
caloric intake, and increase physical ac- Background: Women with eating disor- iron-rich or iron-fortified foods in con-
tivity, and be encouraged to consider en- ders such as anorexia nervosa and bu- junction with vitamin C–rich foods to
rolling in structured weight-loss pro- limia nervosa may have higher rates of enhance iron absorption. Women
grams. Strength of recommendation: A; miscarriage, low birthweight, obstetric should consume folate-rich foods daily
quality of evidence: I-b. complications, and postpartum depres- including 400 g of folic acid daily. More
sion. Eating disorders are associated with research is critically needed in the area of
Underweight nutritional, metabolic, endocrine, and the safety and efficacy of fish consump-
Background: Although most discussions psychological changes that have poten- tion and dietary supplements. Health
of health risks associated with weight sta- tially negative effects on fetal develop- care professionals should address opti-
tus focus on overweight and obesity, a ment. Pregnancy was thought to be a rare mal weight gain, healthy diet, and the use
2005 analysis estimating the number of occurrence among women with an- of dietary supplements as a part of pre-
excess deaths in adults are associated orexia nervosa; however, women who conception care. f
with various BMI levels revealed that are below threshold for clinical symp-
33,746 deaths were associated with BMIs toms or are in remission may not have ACKNOWLEDGMENTS
less than 18.5 kg/m.157 Health risks of be- compromised fertility. Women with bu- We thank Dr Mullinare and Dr Siega-Riz for re-
ing underweight include nutrient defi- limia nervosa may have less difficulty viewing our manuscript.
S352 American Journal of Obstetrics & Gynecology Supplement to DECEMBER 2008www.AJOG.org Supplement
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