Marine oil, and other prostaglandin precursor, supplementation for pregnancy uncomplicated by pre‐eclampsia or intrauterine growth restriction
Abstract
Background
Population studies have shown that higher intakes of marine foods during pregnancy are associated with longer gestations, higher infant birthweights and a low incidence of pre‐eclampsia. It is suggested that the fatty acids of marine foods may be the underlying cause of these associations.
Objectives
To estimate the effects of marine oil, and other prostaglandin precursor, supplementation during pregnancy on the risk of pre‐eclampsia, preterm birth, low birthweight and small‐for‐gestational age.
Search methods
We searched the Cochrane Pregnancy and Childbirth Group Trials Register (December 2005), The Cochrane Central Register of Controlled Trials (The Cochrane Library 2005, Issue 2) and MEDLINE (1966 to April 2005).
Selection criteria
All randomised trials comparing oral marine oil, or other prostaglandin precursor, supplementation during pregnancy with either placebo or no treatment. Trials were excluded if their aim was to treat women with established pre‐eclampsia or suspected intrauterine growth restriction.
Data collection and analysis
Two review authors independently assessed trials for inclusion, data extraction and trial quality.
Main results
Six trials, involving 2783 women, are included in this review. Three of these were rated as high quality, including the largest trial with 1477 women. Women allocated a marine oil supplement had a mean gestation that was 2.6 days longer than women allocated to placebo or no treatment (weighted mean difference (WMD), 2.55 days, 95% confidence interval (CI) 1.03 to 4.07 days; 3 trials, 1621 women). This was not reflected in a clear difference between the two groups in the relative risk (RR) of birth before 37 completed weeks, although women allocated marine oil did have a lower risk of giving birth before 34 completed weeks' gestation (RR 0.69, 95% CI 0.49 to 0.99; 2 trials, 860 women). Birthweight was slightly greater in infants born to women in the marine oil group compared with control (WMD 47 g, 95% CI 1 g to 93 g; 3 trials, 2440 women). However, there were no overall differences between the groups in the proportion of low birthweight or small‐for‐gestational age babies. There was no clear difference in the relative risk of pre‐eclampsia between the two groups.
Authors' conclusions
There is not enough evidence to support the routine use of marine oil, or other prostaglandin precursor, supplements during pregnancy to reduce the risk of pre‐eclampsia, preterm birth, low birthweight or small‐for‐gestational age.
PICOs
Plain language summary
Marine oil, and other prostaglandin precursor, supplementation for pregnancy uncomplicated by pre‐eclampsia or intrauterine growth restriction
Not enough evidence to say if fish oil supplementation in pregnancy helps reduce the risk of pre‐eclampsia and small‐for‐date babies.
Pre‐eclampsia in the mother and a baby being born too soon or too small are relatively common complication of pregnancy that can sometimes seriously affect the health of the baby and the mother. Omega‐3 fatty acids found in fish/marine oils may prevent these complications. This review identified six trials involving 2755 women. The findings were that fish/marine oil supplements taken in pregnancy increase the length of pregnancy by two to three days, slightly increase a baby's birth weight and slightly reduce the number of babies born before 34 weeks gestation. However, these small effects did not reduce the overall risk of a baby being born too soon or too small, nor the mother developing pre‐eclampsia. It is likely that a large number of women participating in trials is needed to address this question fully, and to answer the question is supplementation harmless. Further research is needed.
