Folic acid supplements of 400 micrograms a day are widely recommended for women of childbearing age to prevent birth defects that can affect the spinal cord and brain. Some small studies have recently suggested that the supplements might increase the likelihood of multiple births. But this large, population-based study involving more than 240,000 women found folic acid supplementation did not cause any increase in the rate of multiple births.
Researchers say multiple births carry an increased risk of complications for both mother and child, including low birth weight, premature delivery, and developmental problems.
In the study, researchers from the CDC and China compared the number of multiple births from 1993 to 1995 among 242,015 Chinese women who took 400 micrograms of folic acid per day before or during early pregnancy to the rates among women who didn't take the supplements. Both groups had a rate of multiple births of about 0.6%, and the number of such births was even slightly lower among folic acid users.
The results appear in the Feb. 1 issue of The Lancet.
Researchers say the findings should calm any reservations women might have about taking folic acid supplements, which have clearly been proven to help reduce the risk of neural tube defects.
"Our findings suggest that consumption of 400 micrograms of folic acid alone per day, before and during early pregnancy, does not increase a woman's likelihood of having a multiple birth, whether taken before the estimated date of ovulation, around the estimated time of fertilization, or after conception," writes researcher Robert J. Berry, MD, of the CDC, and colleagues. "In all instances, the rate of multiple births was lower in women who took folic acid than in those who did not take folic acid."
SOURCE: The Lancet, Feb. 1, 2003.