Third-trimester polyunsaturated fatty acid supplementation and increased blood loss at vaginal delivery: A prospective birth cohort study.

The association between polyunsaturated fatty acid (PUFA) supplementation, particularly omega-3 and omega-6 fatty acids, during the third trimester of pregnancy and obstetric outcomes is not well established. This prospective birth cohort study included 12,050 women who delivered at Kuopio University Hospital (KUH) between 2013 and 2024, and completed a questionnaire about supplementation after 28 weeks of gestation. Data were obtained from the KUH Birth Register and the questionnaire. The primary outcomes were maternal blood loss and the incidence of postpartum haemorrhage (PPH), while secondary outcomes included pregnancy complications and neonatal well-being. Approximately 10 % of women reported daily PUFA supplementation during the third trimester. Regular daily use was associated with significantly greater blood loss in vaginal deliveries, although the increase was modest. A trend towards increased PPH was observed among PUFA users, whereas no similar association was found among women undergoing caesarean delivery. PUFA users tended to have a lower prevalence of pre-eclampsia, and their newborns had fewer low Apgar scores at 1 and 5 min, whereas no significant differences in umbilical artery pH or base excess values were observed between PUFA users and non-users. Discontinuing PUFA supplementation approximately 1 month before the expected date of delivery or elective caesarean delivery may be reasonable. However, the potential beneficial effects of PUFA supplementation on the development of pre-eclampsia warrant further investigation in future studies.