Prostanoid excretion in incipient singleton and twin pregnancies

OBJECTIVE: Our purpose was to examine the urinary excretion of metabolites of prostacyclin, 6-keto-prostaglandin F1α and 2,3-dinor-6-keto-prostaglandin F1α, and thromboxane A2, thromboxane B2 and 2,3-dinor-thromboxane B2, in early twin and singleton pregnancies resulting from in vitro fertilization–embryo transfer. STUDY DESIGN: Overnight urine samples were obtained from 23 women at regular intervals for 20 weeks after embryo transfer. Prostanoids were measured by high-pressure liquid chromatography–radioimmunoassay. RESULTS: All prostanoids, most markedly 6-keto-prostaglandin F1α and 2,3-dinor-6-keto-prostaglandin F1α, increased in both singleton and twin pregnancies. This resulted in an increased ratio of prostacyclin over thromboxane A2 both in the dinor compounds (from 1.3 to 2.8) and the total metabolites (from 1.7 to 3.5). No marked differences were observed between twin and singleton pregnancies. CONCLUSIONS: Twin and singleton pregnancies show a similar increase in the prostacyclin to thromboxane A2 ratio in the first half of pregnancy. (AM J OBSTET GYNECOL 1996;174:1614-7.)