Early preterm birth (six or more weeks early) is one of the primary contributors to disability and death in children under the age of five years. Infants born early preterm are more likely to experience neurodevelopmental, respiratory, and gastrointestinal difficulties. Currently, physicians do not have reliable markers by which to predict whether a woman is at risk for an early preterm birth. Nearly 3 percent of infants born in the United States are early preterm. Findings from a new study suggest that maternal high-dose docosahexaenoic acid (DHA) supplementation during pregnancy reduces the risk of early term birth.

DHA is an omega-3 fatty acid found in fatty fish and other seafood. It plays critical roles in fetal vision and nervous system growth and development. There are no established guidelines for DHA intake for pregnant women, but most prenatal supplements include DHA, typically in amounts of approximately 200 milligrams.

The study involved 1,100 pregnant women in the United States. The authors of the study randomly assigned the women to one of two groups, with one half receiving a high dose (1,000 milligram) DHA supplement, and the other receiving a low dose (200 milligram) DHA supplement. Both groups of women took their respective supplements daily for the duration of their pregnancies. The authors noted pregnancy outcomes (such as gestational diabetes, preeclampsia, Cesarean delivery, or others), maternal and infant health status (including DHA levels), and serious adverse events post-delivery (such as birth defects, death, or others).

Among women who took the higher dose of DHA, 1.7 percent gave birth early preterm; among those who took the lower dose, 2.4 percent gave birth early preterm. However, if they had low DHA levels at the beginning of the study, they were half as likely to give birth early preterm if they took the higher dose, compared to those who took the lower dose. Timing was important, too, with lower risk associated with taking the supplements in the first half of pregnancy, rather than the last half. Women who had higher levels of DHA at the beginning of the study had a 1.2 percent risk of giving birth early preterm birth, and this risk did not change when taking a high dose DHA supplement.

These findings suggest that high-dose DHA supplementation during pregnancy reduces the risk of early preterm birth and provide evidence for establishing recommended intakes for pregnant women. The authors recommended that physicians measure DHA levels in pregnant women and offer high-dose DHA supplements to those whose levels are low.

• Link to full study.