Most women tend to think of the time period during their pregnancy and lactation as the area of focus for their nutritional and lifestyle improvement efforts. Increasingly though, practitioners, consumers and patients alike, are realizing that not only does taking care of oneself during the reproductive years affect a healthy pregnancy and offspring, but nutritional habits and supplementation during a preconception focused time period, has benefits as well. With an increasing prevalence of risk factors for a less than optimal pregnancy and miscarriage, such as poor nutrition, infections, allergies and environmental pollution, we can modernize and revive a practice with a long history—that of preparing for pregnancy and improving one’s health in order to conceive and bear a child.
Nearly all women can benefit from nutritional and multivitamin supplementation four to twelve months before and all during pregnancy, and throughout labor, delivery, and breast-feeding.
Numerous nutrients are associated with one or more facets of an optimal pregnancy whether it be reducing miscarriage, preventing birth defects, enhancing normal fetal development, preventing premature and low-birth weight infants, or preventing preeclampsia. While the list of important nutrients is long, three key nutrients stand out.
Essential fatty acids
Essential fatty acids (EFAs) have a unique role during pregnancy because of the rapid development of new cell growth, new tissues, and new organ systems in a developing fetus. Fetal development is associated with a high EFA requirement, and this supply is dependent on the amount and availability of EFAs from the mother.
Maternal levels of omega-3 fatty acids, especially DHA, decrease during pregnancy. EFAs are components of breast milk and maternal levels may be reduced further in nursing women. For the fetus, a deficiency of EFAs, particularly EPA and DHA, may lead to a poorly developed central nervous system. EFA deficiency may also lead to intrauterine growth retardation leading to a lower whole body weight and slower growth of the brain.
Trials on omega-3 fatty acids conducted in pregnant women have shown a significant reduction in the incidence of premature delivery. In one such study, fish oil was investigated for its effects on pregnancy duration, birth weight, intrauterine growth restriction, and pregnancy-induced hypertension. Omega-3 fatty acid supplementation of 2.7 grams per day was compared to olive oil and/or no supplement. The fish oil-supplemented pregnancies lasted four days longer and birth weight was 107 gm greater. In another study, infants born of mothers who had been given cold liver oil had higher levels of DHA in their umbilical cord, and a longer gestation. Fish oil also appeared to be related to a reduction in the risk of preterm delivery in those women who had had a previous preterm delivery.  In a study of pregnant women in Iceland those consuming liquid cod liver oil in the first 15 weeks of pregnancy had babies with higher birth weight.
Prostaglandins, as determined by EFA status, are also involved in the development and clinical expression of preeclampsia. These prostaglandins are modulators of vascular smooth muscle tone and platelet aggregation (blood platelets sticking together). Preeclampsia is characterized by increased vasoconstriction, frequently associated with increased platelet aggregation, reduced uteroplacental blood flow, and premature delivery. In a placebo-controlled clinical trial, a group of pregnant women receiving a combination of evening primrose oil (EPO) and fish oil had a significantly lower incidence of edema. 
There is some evidence that EPO, taken both orally and vaginally can be used to promote cervical ripening. Clinically, EPO supplementation during pregnancy has been found by practitioners of natural childbirth to be an efficacious method to stimulate cervical ripening during labor, and PGE1 is known to stimulate cervical ripening and hasten the progression of labor. Although practitioners using this supplement report no adverse effects, a retrospective trial comparing the oil to no supplement did not note a difference between groups and there was a suggestion that there was an increased incidence of premature rupture of membranes, labor augmentation, and assisted vaginal delivery in the evening primrose group.
There are cautions about increased fish intake due to the mercury content. The Food and Drug Administration advises no more than 12 oz of fish / week, due to concerns about mercury content in fish and potential for adverse effects on the infant. Numerous nutrition groups point out that if women focus on the low mercury fish, that women should in fact eat a minimum of 12 oz of fish per week, in order to assure an adequate amount of essential fatty acids.
Supplementation with a daily complex of essential fatty acids and fish oils during pregnancy provides vital nutrients that supply the necessary EFAs for the increased nutritional and metabolic demand throughout the nine months of gestation.
Folic acid is the only vitamin whose requirement doubles during pregnancy. Deficiencies of folic acid have been linked to low birth weight infants and neural tube defects. According to one controlled study, women at high risk (having previously given birth to babies with neural tube defects) who were given folate supplementation showed a 72 percent protective effect compared to the placebo group.  In another study, a group of pregnant women given folate supplementation gave birth to infants with increased birth weight and Apgar scores and had a decreased incidence of fetal growth retardation and maternal infections. 
In 1996, the U.S. Preventive Services Task Force (USPSTF) recommended that all women planning a pregnancy or possibly being able to become pregnant take a multivitamin supplement that contains folic acid, for the prevention of neural tube defects. The USPSTF has recently issued a new updated statement in the May 5, 2009 issue of Annals of Internal Medicine. This statement is an update of the 1996 USPSTF recommendation. Based on the observational evidence and randomized controlled trials published since 1996, the USPSTF found convincing evidence that supplements containing 0.4 to 0.8 mg of folic acid during the preconception period lowers the risk for neural tube defects. They also concluded that adequate evidence suggests that folic acid from supplementation at usual doses is not associated with serious harm. Including no evidence found for the masking of vitamin B12 deficiency in women of childbearing age. For women who are planning or are capable of pregnancy, the USPSTF concludes that there is a high certainty that the overall benefit of folic acid supplementation during pregnancy is substantial.
Zinc is required for proper fetal growth and immunity. Plasma zinc levels decline about 30 % during pregnancy,  and low zinc intake is associated with spontaneous abortion and premature delivery,  as well as complications and labor abnormalities.  Low zinc was also associated with the specific complication of fetal distress, and may be associated with CNS abnormalities in infants, including neural tube defects, , as well as low birth weight infants ,, and toxemia of pregnancy. Supplementation, especially if zinc levels are low, is recommended to reduce the risk of fetal and maternal complications. In one study, labor complications (vaginal bleeding, fetal acidosis, uterine inertia) were improved. Another study showed a lower incidence of pregnancy-induced hypertension (which is associated with preeclampsia and preterm labor). Some food sources of zinc are oysters, beets, broccoli, wheat germ, wheat bran, fish, and lentils; and watercress (not in the first trimester).
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