A pre-pregnancy year of folic acid sharply lowers risk of very premature birth

Taking folic acid supplements for a year before conception reduces the risk of very premature birth by at least 50%, researchers reported Monday.

Shorter courses of the supplement were not as effective, according to the study of nearly 35,000 women reported in the Public Library of Science journal PLoS Medicine.

Folic acid's effectiveness in reducing the risk of neural-tube and other birth defects -- even without such a long course -- is long established. The discovery that it can also reduce the risk of preterm birth "is very significant," said Dr. Diane Ashton, deputy medical director of the March of Dimes Birth Defects Foundation, who was not involved in the study.