Vaginal and abdominal delivery increases maternal urinary 6-keto-prostaglandin F1α excretion

Summary. To study the role of the antiaggregatory and vasodilatory prostacyclin (PGI₂) during human delivery, serial urine samples collected from 13 women delivered vaginally and from eight delivered abdominally were assayed for 6-keto-prostaglandin F_1α (6-keto-PGF_1α a breakdown product of PGI₂) by high-performance-liquid-chromatography and radioimmunoassay. In women delivered vaginally the mean urinary 6-keto-PGF_1α concentration was 41.9 (SE 8.3) ng/mmol creatinine, before the onset of labour and increased progressively to a maximum of 186.5 (SE 47.6) ng/mmol creatinine 2 h after delivery irrespective of the use of oxytocin and epidural analgesia. In women delivered by caesarean section under epidural anaesthesia, the urinary 6-keto-PGF_1α rose from 33.4 (SE 4.2) ng/mmol creatinine to 2153 (SE 314) ng/mmol creatinine 2 h after section. In both groups the increased levels had fallen by 24 h postpartum to levels below those found before delivery. In neonatal urine 6-keto-PGF_1α concentrations were some 12–30 times higher than those in postpartum urine. Thus, vaginal and abdominal delivery is accompanied by significant increases in maternal PGI₂ release, perhaps in the myometrium and/or intrauterine tissues. This may be of significance in the regulation of fetoplacental blood flow and in the prevention of intra- and postpartum thrombosis.