Taking folic acid before and during pregnancy does not decrease a woman's risk of pre-term birth, a new study suggests.

Norwegian researchers were unable to find a statistically significant association between a mother's folic acid consumption and premature birth in their study of more than 70,000 children.

But women of reproductive age should still take folic acid for other health reasons, said Lynn Bailey, a folate expert and professor of food science and human nutrition at the University of Florida, who was not involved with the study.

"To say that folic acid won't reduce the risk [of premature birth] doesn't take away from the fact that one of the most important public health discoveries in this century is that folic acid does significantly reduce risk of neural tube defects," Bailey told MyHealthNewsDaily.

Neural tube defects include spina bifida, which occurs when the tube that forms the spine and spinal cord doesn't close correctly, and anencephaly, in which the brain does not fully develop, according to the National Institutes of Health.

The new study was presented today (Feb. 10) at the Society for Maternal-Fetal Medicine's annual meeting in San Francisco.

Looking at the evidence

Researchers gathered premature birth and folic acid supplementation data from 72,989 children who were part of the Norwegian Mother and Child Cohort Study. Of those children, 955 were born prematurely.

Folic acid supplementation did not significantly affect who was born prematurely and who was born at full-term, the study said.

However, the finding conflicts with the results of some previous studies. For example, a 2009 study in the journal PLoS Medicine showed that women who took folic acid supplements for at least a year before conception had 50 to 70 percent fewer pre-term births than women who didn't take folic acid.

The conflicting evidence may be explained by the fact that these are all observational studies and not randomized controlled trials, Bailey said.

Folic acid's role in preventing neural tube defects has been demonstrated in randomized, controlled trials, in which "you're actually giving the nutrient, and you're observing the outcome, so you can make a conclusion regarding cause and effect," she said. But with observational studies like the new one, you can't rule out that the results may at least partially be due to chance, she said.

The discrepancy between the 2009 findings and the new findings could also be a result of study design, said study researcher Dr. Verena Sengpiel, of Sahlgrenska University Hospital/Östra in Sweden.

The 2009 study found an association between folic acid supplementation a year before conception, but "we didn't compare up to a year," Sengpiel told MyHealthNewsDaily.

Dangers of pre-term births

For the past 15 years, the U.S. government has required that enriched grain products include folic acid. And public health agencies recommend that women of childbearing age take 400 micrograms of folic acid a day to reduce the risk of giving birth to a child with neural tube defects.

"Many women are not aware that they are pregnant in the beginning, and that's why the recommendations are extended to all reproductive-age women," said Dr. Radoslaw K. Bukowski, author of the 2009 study and an assistant professor of obstetrics and gynecology at the University of Texas Medical Branch, who was not involved with the new study.

There are not many proven ways to prevent pre-term birth, Bukowski said.

Some studies have shown that progesterone injections can work in women who have delivered prematurely before, or who have a short cervix. But these women only make up about 5 percent of the female population, he said.

Premature births (births before 37 weeks of pregnancy) are the leading cause of neonatal death, according to the Centers for Disease Control and Prevention. More than 12 percent of U.S. babies born each year are premature.

"Even the babies who survive, depending on how early they are born, have a very high rate of complications ," Bukowski told MyHealthNewsDaily. Such complications include breathing problems, brain bleeds, bowel inflammation and infection.

The exact cause of premature birth is still unknown, Bailey said. But researchers are getting closer to finding what causes it and how to prevent it, she said.

"Scientists have been working hard to unravel that, but they unfortunately still don't know the answer," Bailey said. But "the data we have will lay a foundation for more controlled trials."

Pass it on: Folic acid may not prevent preterm births, according to a new study, but it's still important in preventing neural tube defects in babies like spina bifida.

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