Folic acid supplementation does not increase risk for twins

Last published / updated 05/09/2005

Folic Acid prevents birth defects

For some time now, I have been recommending that women who are attempting to become pregnant should take 1000 micrograms of folic acid daily to reduce the risk of having a baby with birth defects. The birth defects are known as neural tube defects and include such problems as spina bifida and anencephaly. Recent data have shown that since these recommendations have gone into effect that the rate of neural tube defects has dropped significantly. Folic acid, also called folate is a B vitamin found in foods such as spinach and other leafy greens, beans and orange juice. Despite the addition of folic acid to many breakfast cereals, breads and other grains, many women have a difficult time getting the required amound on a daily basis. Thus, prenatal vitamins containing folic acid have been recommended. In the United States, fortifiaction of foods has been required since 1998.

Folic acid and twinning

Some studies have suggested that the rate of twinning has risen since the introduction of fortification. The largest effect was reported in a Swedish study that reported a 45% increase in multiple gestation if a woman use folic acid before pregnancy. However, several studies since 1999 have attributed the increase risk to the greater use of fertility treatments and not from the use of folic acid itself. In a study about to be released in the journal Epidemiology, of more than 176,000 Norwegian women who gave birth between 1998 and 2001, researchers found no evidence that pre-pregnancy folic acid use increased the chances of a twin pregnancy. Initially, the study looked at women who took folic acid before pregnancy without regard to how they became pregnant. These women were 59 percent more likely to have twins than women who did not take folate supplements. However,

there was no increase in risk when only women who conceived naturally were studied.

The conclusion is that women who undergo in vitro fertilization are much more likely than other women to have multiple births, and they are also much more likely to take folic acid before getting pregnant. About 25% of women who conceived through IVF took pre-pregnancy folic acid, versus only six percent of those who conceived naturally.