THURSDAY, Jan. 30, 2003 (HealthDayNews) -- Folic acid has been widely touted for its ability to reduce birth defects, such as spina bifida, in growing fetuses when taken before conception and during pregnancy.
However, several small studies have suggested the nutrient might increase the incidence of twins.
Not so, say researchers from the U.S. Centers for Disease Control and Prevention (CDC) and the Peking University Health Sciences Center in China. Their study appears in this week's issue of The Lancet.
"This is good news for women around the world," says study co-author Dr. Robert Berry, a medical epidemiologist with the CDC. "The consumption of folic acid does not increase a woman's chance of having twins."
Since public health officials began recommending consumption of folic acid before pregnancy in 1992, the rate of spina bifida has dropped 32 percent, according to the CDC.
However, because multiple pregnancies are often more complicated than single pregnancies, health-care professionals were concerned that recommending folic acid to reduce spina bifida and other neural tube defects could inadvertently increase the rate of twins. Twins and other multiple pregnancies are more likely to be born prematurely and have growth problems, according to the American College of Obstetricians and Gynecologists.
Berry and his colleagues reexamined data that had been collected for a study on the effectiveness of folic acid. The study included almost 250,000 young Chinese women with an average age of 24. About half of the women took 400 micrograms of folic acid daily before and during their pregnancies. The women didn't take any other vitamin supplements.
Nearly 1,500 women from the whole group had twins. The rate of multiple births was 0.59 percent for women who took folic acid and 0.65 percent for women who didn't. That difference is not statistically significant, according to the study.
Berry says researchers aren't sure why past studies linked folic acid to an increase in the rate of twins, but he suspects it may have something to do with the participants in the other studies. For example, one of the studies was done on older women, who naturally have a higher rate of multiple pregnancies.
Dr. Elizabeth Ginsburg, a reproductive endocrinologist at Exeter Hospital in New Hampshire, agrees that some other factor, such as maternal age, was probably the reason for the higher twin rates seen in previous studies.
One weakness of the new study, she says, is the researchers didn't ask the women about their diets. She says it would have been useful to know how much folic acid the women were getting in the foods they ate.
More information
To learn more about the benefits of folic acid, visit the March of Dimes. For more information on multiple pregnancy, read this from the American College of Obstetricians and Gynecologists.
