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There are limited studies exploring the effects of n-3 PUFA supplementation on pregnancy outcomes. The goal of this study was to review relevant studies in order to determine the effect of n-3 polyunsaturated fatty acid (n-3 PUFA) supplementation on pregnancy outcomes based on eligible randomized controlled trials (RCTs).

Material and methods:
Qualified studies were searched by keywords in PubMed, the Cochrane library and Embase. Studies from other pertinent sources were also reviewed, and RCTs published before January 2021 were reviewed. For each study, we assessed and synthesized the outcomes by relative risk (RR) or weighted mean difference (WMD) combined with 95% confidence interval (95% CI).

We included 13 studies with 9069 patients. Compared with the control group, n-3 PUFA significantly decreased the incidence of preterm delivery (RR: 0.898, 95%CI: 0.819~0.984) and low birthweight (RR: 0.797, 95%CI: 0.655~0.970); increased the birth weight (WMD: 99.340, 95%CI: 10.503~188.177) and birth length (WMD: 0.449, 95%CI: 0.236~0.663). There was no significant difference in pregnancy-induced hypertension, preeclampsia, intrauterine growth retardation (IUIG), early preterm delivery, anti-hypertensive therapy, gestational diabetes and head circumference at birth between the two groups.

The available evidence shows that n-3 PUFA is not beneficial in reducing the incidence of maternal pregnancy outcomes such as gestational diabetes mellitus and hypertension; but it is beneficial to neonatal health such as decreasing the incidence of preterm delivery and low birthweight and increasing birth weight and birth length.