Fish Oil in Various Doses or Flax Oil in Pregnancy and Timing of Spontaneous Delivery: A Randomized Controlled Trial

Abstract

Previous studies have suggested that a diet containing long-chain n-3 fatty acids derived from fish oil may delay spontaneous delivery. The investigators, in a randomized, controlled trial, addressed this hypothesis and also sought to determine whether alpha-linolenic acid (ALA), in the form of flax oil capsules, might have the same effect. Participants were 3098 women who reported a low intake of fish and who were randomized to receive one of 5 doses (0.1, 0.3, 0.7, 1.4, or 2.8 g) of eicosapentaenoic acid and docosahexaenoic acid daily, 2.2 g daily of ALA, or no treatment. Supplementation began at 17 to 27 weeks gestation and continued until delivery. The treatment groups were similar with respect to age, parity, gestational age, fish consumption, body mass index, and smoking. Analyzing singleton live-born pregnancies, no significant difference in gestational length was found between control women and any of the treatment groups whether comparing mean gestational ages or hazard rates of spontaneous delivery. This held for both intention-to-treat analyses and analyses based on the participants only. There were no apparent differences in intake of any of the fatty acids between the treatment groups. The difference in time to spontaneous delivery between pregnant women given the highest dose of fish oil and control women was less than 1 day. A majority of women in the treatment groups failed to continue taking their capsules up to the time of delivery. These findings may indicate that there is in fact no meaningful effect of dietary n-3 fatty acids on the timing of spontaneous delivery. It also is possible that there is a rapidly diminishing effect that depends on continued supplementation.