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Folic acid reduces risk of miscarriage and stillbirth

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Folic acid is a vitamin essential vitamin for all humans. It is especially important to have adequate folic acid before and during pregnancy because it reduces the risk of neural tube defects (abnormalities of the brain and spinal cord). A new study has found that women who do not have adequate folic acid intake or at increased risk for stillbirth and miscarriage. The study was published in the July edition of the journal Obstetrics & Gynecology by researchers Harvard School of Public Health, Harvard Medical School, and Brigham and Women's Hospital, all in Boston, Massachusetts.

The study authors note that approximately one third of pregnancies are lost after the embryo implants in the uterus, often before a pregnancy is diagnosed; thus, pregnancy loss the most frequent adverse pregnancy outcome. Chromosomal abnormalities are involved in approximately 50% of all miscarriages, the remaining 50% may be preventable and are related to environmental factors. They explain that the role of dietary factors in human reproduction is limited; however, it is extremely likely that intake of certain nutrients, particularly folate, could positively influence the odds of a successful pregnancy outcome. Folic acid prevents neural tube defects; thus, the American College of Obstetricians and Gynecologists recommends that all women planning or capable of pregnancy take 400 micrograms of folic acid daily.

The authors explain that folic acid supplementation may have reproductive benefits beyond the prevention of neural tube defects. Supplementation with the vitamin in animals promotes embryo and fetal survival rates throughout pregnancy; however, the association between its intake and fetal survival in humans is less clear. Therefore, they conducted a study to assess the relationship between pre-pregnancy folic acid intake and risks of miscarriage and stillbirth in a large group of women who had a wide range of folic acid intake. The goal was to expand on previous studies by examining dose–response relationships comparing food with supplemental folate. They theorized that higher folic acid intake of folate, particularly supplemental folate, is associated with reduced risk of pregnancy loss. They explain that folic acid supplements are more readily absorbed and available to the body than folic acid from food.

The study group comprised women in the Nurses' Health Study II who self-reported a pregnancy between 1992 and 2009. Dietary folic acid and supplement use was assessed every four years, beginning in 1991, via a food frequency questionnaire. Pregnancies were self-reported with pregnancies lost spontaneously (spontaneous loss at less than 20 weeks of gestation and stillbirth at 20 or more weeks of gestation); these pregnancies were compared to pregnancies terminating in ectopic pregnancy, induced abortion, or live birth.

The investigators found that among the 11,072 women, 15,950 pregnancies were reported; 2,756 (17.3%) ended in spontaneous abortion and 120 (0.8%) ended in stillbirth. Compared with women in the lowest quintile (20%) of pre-pregnancy folic acid intake (less than 285 micrograms per day), those in the highest quintile (greater than 851 micrograms per day) had a relative risk of spontaneous abortion of 0.91. They noted that this association was primarily due to intake of folate from supplements. Compared with women without supplemental folate intake (0 micrograms per day), those in the highest category (greater than 730 micrograms per day) had a relative risk of spontaneous abortion of 0.80. The association of pre-pregnancy supplemental folate with risk of spontaneous abortion was consistent across gestational period of loss. A similar reduction was found regarding the risk of stillbirth; however, the rate did not quite reach statistical significance.

The authors concluded that higher intake of folate from supplements was associated with reduced risk of miscarriage. They recommended that women who might become pregnant should use supplemental folic acid for neural tube defect prevention and because it may decrease the risk of miscarriage.

Take home message:

Folic acid occurs naturally in many foods; among plants, are especially plentiful in dark green leafy vegetables. These foods are healthy and should be consumed; however, women who are pregnant or could possibly become pregnant should take a supplement. Folic acid is a component of all prenatal vitamins.