Vitamins that may be helpful
Most doctors, many other healthcare professionals, and the March of Dimes recommend that
all women of childbearing age supplement with 400 mcg per day of folic acid. Such supplementation could protect against
the formation of neural tube defects (such as spina bifida) during the time between conception
and when pregnancy is discovered.
The requirement for the B vitamin folic acid doubles during pregnancy, to 800 mcg per day
from all sources.27 Deficiencies of folic acid during pregnancy have been linked to
low birth weight28 and to an increased incidence of neural tube defects (e.g.,
spina bifida) in infants. In one study, women who were at high risk of giving birth to babies
with neural tube defects were able to lower their risk by 72% by taking folic acid supplements
prior to and during pregnancy.29 Several preliminary studies have shown that a
deficiency of folate in the blood may increase the risk of stunted growth of the
fetus.30 31 32 33 34 35
36 37 This does not prove, however, that folic acid supplementation
results in higher birth weights. Although some trials have found that folic acid and iron, when taken together, have improved birth
weights,38 39 40 41 other trials have found
supplementation with these nutrients to be ineffective.42 43
The relationship between folate status and the risk of miscarriage is also somewhat
unclear. In some studies, women who have had habitual miscarriages were found to have elevated
levels of homocysteine (a marker of folate
deficiency).45 46 47 48 In a preliminary study, 22
women with recurrent miscarriages who had elevated levels of homocysteine were treated with 15
mg per day of folic acid and 750 mg per day of
vitamin B6, prior to and throughout their next
pregnancy. This treatment reduced homocysteine levels to normal and was associated with 20
successful pregnancies.49 It is not known whether supplementing with these vitamins
would help prevent miscarriages in women with normal homocysteine levels. As the amounts of
folic acid and vitamin B6 used in this study were extremely large and potentially toxic, this
treatment should be used only with the supervision of a doctor.
In other studies, however, folate levels did not correlate with the incidence of habitual
miscarriages.50 51 52
Preliminary53 and double-blind54 evidence has shown that women who
use a multivitamin-mineral formula containing
folic acid beginning three months before becoming pregnant and continuing through the first
three months of pregnancy have a significantly lower risk of having babies with neural tube
defects (e.g., spina bifida) and other congenital defects.
In addition to achieving significant protection against birth defects, women who take folic acid supplements during pregnancy have been
reported to have fewer infections, and to give birth to babies with higher birth weights and
better Apgar scores. 55 (An Apgar score is an evaluation of the well-being of a
newborn, based on his or her color, crying, muscle tone, and other signs.) However, if a woman
waits until after discovering her pregnancy to begin taking folic acid supplements, it will
probably be too late to prevent a neural tube defect.
Biotin deficiency may occur in as many as
50% of pregnant women.56 As biotin deficiency in pregnant animals results in birth
defects, it seems reasonable to use a prenatal multiple vitamin and mineral formula that
In a preliminary study, pregnant women who used a zinc-containing nutritional supplement in the three
months before and after conception had a 36% decreased chance of having a baby with a neural
tube defect, and women who had the highest dietary zinc intake (but took no vitamin
supplement) had a 30% decreased risk.57
Iron requirements increase during
pregnancy, making iron deficiency in pregnancy quite common.58 Iron supplement use
in the United States is estimated at 85% during pregnancy, with most women taking supplements
three or more times per week for three months.59 Pregnant women with a documented
iron deficiency need doctor-supervised treatment. In one study, 65% of women who were not
given extra iron developed iron deficiency
during pregnancy, compared with none who received an iron supplement.60 However,
there is a clear increase in reported side effects with increasing supplement amounts of iron,
especially iron sulfate.61 62 Supplementation with large amounts of iron
has also been shown to reduce blood levels of zinc.63 Although the significance of
that finding is not clear, low blood levels of
zinc have been associated with an increased risk of complications in both the mother and
Iron supplementation was associated in one study with an increased incidence of birth
defects,65 possibly as a result of an iron-induced deficiency of zinc. Although
additional research needs to be done, the evidence suggests that women who are supplementing
with iron during pregnancy should also take a
multivitamin-mineral formula that contains adequate amounts of zinc. To be on the safe
side, pregnant women should discuss their supplement program with a doctor.
Supplementation with fish oil (providing
either 2.7 g or 6.1 g per day of the omega-3 fatty acids EPA and DHA) significantly reduced recurrence of premature
delivery, according to data culled from six clinical trials involving women with a high risk
for such complications.66 Fish oil supplementation did not prevent premature
delivery of twin pregnancies, nor did it have any preventive effect against intrauterine
growth retardation or pregnancy-induced hypertension. Fish oils should be free of
contaminants, such as mercury and organochlorine pesticides. Women who eat substantial amounts
of certain types of seafood (e.g., swordfish, tuna) may be consuming contaminants that can increase
the risk of brain and nervous system abnormalities in their offspring. Exposure to mercury and
polychlorinated biphenyls (PCBs) was found to be increased in relation to maternal intake of
seafood. Higher exposure to these toxic contaminants has been linked to an increased risk of
deficits in the developing brains and nervous systems of the children.67
S-adenosylmethionine (SAMe) supplementation
has been shown to aid in the resolution of blocked bile flow (cholestasis), an occasional
complication of pregnancy.68 69
Premature rupture of membranes (PROM) affects 10 to 20% of all pregnancies. It is an
important cause of preterm delivery and is associated with increased rates of complications in
both the mother and child. In a double-blind study, supplementing with 100 mg of vitamin C per day, beginning in the twentieth week of
pregnancy, reduced the incidence of PROM by 74%.70 The women in this study were
consuming only about 65 mg of vitamin C per day in their diet, which is less than the RDA of
80 to 85 mg per day for pregnant women.
Calcium needs double during
pregnancy.71 Low dietary intake of this mineral is associated with increased risk
of preeclampsia, a potentially dangerous (but
preventable) condition characterized by high blood pressure and swelling. Supplementation with
calcium may reduce the risk of pre-term delivery, which is often associated with preeclampsia.
Calcium may reduce the risk of pregnancy-induced
hypertension,72 though these effects are more likely to occur in women who are
calcium deficient.73 74 Supplementation with up to 2 grams of calcium
per day by pregnant women with low dietary calcium intake has been shown to improve the bone
strength of the fetuses.75
Pregnant women should consume 1,500 mg of
calcium per day from all sources—food plus supplements. Food sources of calcium
include dairy products, dark green leafy vegetables, tofu, sardines (canned with edible bones), salmon (canned with edible bones), peas, and
Are there any side effects or interactions?
Refer to the individual supplement for information about any side effects or interactions.
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