(17-09-11) Moderate Fish Consumption Associated with Lower Risk of Recurrent Preterm Delivery

The relationship between the frequency of fish consumption and the chance of preterm birth remains controversial because research findings are inconsistent. It has been suggested that fish consumption or higher long-chain omega-3 PUFA (n-3 LC-PUFA) intakes may prolong gestation only in women with habitually low fish intakes. This might imply a threshold effect for n-3 LC-PUFAs in pregnancy. Low fish or n-3 LC-PUFA intakes in early pregnancy or before conception might also affect embryonic development. Increased n-3 LC-PUFA intake prior to conception was reported to improve embryo morphology.Investigators at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Md., conducted a randomized clinical trial to evaluate the effect of n-3 LC-PUFA supplementation in the second half of pregnancy on the risk of preterm birth in high-risk women. Published results from the trial indicated that supplementation with 2 g per day of n-3 LC-PUFAs had no significant effect on the risk of recurrent preterm delivery.In a recent report the authors determined whether the fish or n-3 LC-PUFA intakes of the women early in pregnancy might affect their risk of recurrent preterm delivery, defined as birth at less than 37 completed weeks of gestation.Women with a history of at least one previous preterm birth were recruited from 13 centers in the U.S. At randomization to treatment, 852 participants were interviewed about their frequency of consuming 4 different types of fish from the time of their last menstrual period. Participants consuming fish oil or n-3 PUFA supplements were excluded. Data on fish consumption were grouped into one category because of small numbers in some categories. Participants also had their gestational age confirmed by ultrasonography. All women were given weekly injections of 17-alpha-hydroxy-progesterone caproate to reduce the risk of preterm delivery.Fish consumption patterns within the sample varied with ethnicity, with African-American and Hispanic women eating fish significantly more often than non-African-American or non-Hispanic women. Overall, 30% of women reported eating fish less than once per month or never, while 9% ate fish more than 3 times per week.Preterm birth occurred significantly (P < 0.001) more often in women who ate fish once per month or less (49%) compared with women who ate fish more often (36%). As fish consumption increased to approximately 3 fish meals per week, the probability of preterm birth declined, but risk was not reduced with more frequent fish consumption (Table). When the probability of preterm birth was calculated on the basis of red blood cell EPA plus DHA as a percent of total fatty acids at randomization, women with the lowest n-3 LC-PUFA levels had a greater risk of preterm birth compared with women in the higher quartiles, but the overall association was of borderline statistical significance (P = 0.054).This study suggests that fish consumption 2 to 3 times per week is associated with significantly lower risk of preterm birth in high-risk women. Interestingly, higher fish consumption was suggestive of a higher risk. Others have reported that birthweight tends to level off with 3 seafood meals per week.In seeking a plausible explanation why preterm delivery was higher in women who ate fish once per month or less, the investigators suggested that women who do not eat fish very often might have higher intakes of n-6 PUFAs than women who eat fish. Metabolites of n-6 PUFAs, such as prostaglandins and leukotrienes, stimulate uterine contractions and parturition and these effects are counteracted by n-3 LC-PUFAs. One cannot exclude the possibility that other dietary and lifestyle factors may have contributed to the observations reported.
Klebanoff MA, Harper M, Lai Y, Thorp J Jr, Sorokin Y, Varner MW, Wapner RJ, Caritis SN, Iams JD, Carpenter MW, Peaceman AM, Mercer BM, Sciscione A, Rouse DJ, Ramin SM, Anderson GD; for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Fish consumption, erythrocyte fatty acids, and preterm birth.

Source:Obstet Gynecol 2011;117:1071-1077.

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