About 12.7% of all births in the US are premature.  Even though weekly  injections of  hydroxyprogesterone caproate can reduce the risk of preterm birth, the rate of prematurity is still about 36%  among women at high-risk ( or those who have previously delivered preterm). The purpose of this study was to determine whether omega-3 fatty acid supplements could offer additional benefits to women at high-risk of a preterm delivery.

The study design involved a randomized, controlled, double-blind trial, conducted through 13 centers in the US.  Pregnant women, who had previously given birth to at least one premature baby, were enrolled in the study between 16-21 weeks gestation. All women were given an injection of  hydroxyprogesterone caproate and followed for one week to see if they were able to comply with the study’s procedure. After one week, the women were randomly assigned either to a control group (given a placebo with mineral oil) or to the treatment group (given a supplement of omega-3 fatty acids). The omega-3-fatty acid supplement contained 1200 mg eicosapentaenoic acid and 800 mg docosahexanoic acid. The main outcome of interest was delivery before 32, 35, or 37 weeks. Other important outcomes included hemorrhage, birth weight, infant admission to the Intensive Care Unit, retinopathy, and necrotizing enterocolitis.

Among the 3755 women who were screened for the study, 994 passed the compliance test and 852 were randomly assigned to either the treatment or control group. Compliance with the study protocol was similar: 85% in the treatment and 90.9% in the control group. Although the supplements did raise the level of omega-3 fatty acids in the blood of the treatment mothers, no differences was observed in the risk of delivery before 32, 35, and 37 weeks. There were no differences in birth weight, small-for-gestational age, retinopathy, necrotizing enterocolitis, or length of time spent in the intensive care unit. However, infants born to mothers taking omega-3-fatty acids were likely than control infants to experience respiratory distress, which has not been reported before in other omega-3-fatty acid studies.

 Conclusions and Implications:   In pregnant women who are risk of preterm delivery, omega-3-fatty acids supplements do not appear to provide an added benefit in lowering risk. In fact, there may even be an increased risk of respiratory distress.  This outcome may have occurred by chance but further research is needed.

 Source: Harper M, Thorn E, Klebanoff MA, Thorp J et al . Omega-3 fatty acid supplementation to prevent recurrent preterm birth. Obstet & Gynecol 115 (2) 234-241.