Prostaglandin F_2α metabolite levels in plasma, amniotic fluid, and urine during pregnancy and labor

Levels of 13, 14-dihydro 15-keto-prostaglandin F_2α (dhk PGF_2α) in the plasma of 30 patients as well as in the amniotic fluid of 17 patients, and 5α, 7α-dihydroxy 11-keto tetranor-prostane 1,16-dioic acid (the main urinary metabolite of PGF_2α [PGF_2α MUM]) levels in the urine of 30 patients were measured by radioimmunoassay during pregnancy, labor, and the puerperium. During pregnancy, no increase in dhk PGF_2α (ng/ml) in plasma was detected as the time of delivery approached. The levels of dhk PGF_2α during the second stage (0.64 ± 0.15) and also at delivery (0.88 ± 0.27) were significantly elevated over those in the first stage (0.38 ± 0.29) (P <0.025 and P < 0.005, respectively). Its level 2 hours after delivery was reduced to predelivery levels. Its levels in umbilical arterial and venous blood were 0.71 ± 0.26 and 0.67 ± 0.26, respectively. A significant elevation (P < 0.01) of dhk PGF_2α from 0.89 ± 0.21 before labor to 6.16 ± 2.40 at delivery was found in amniotic fluid. The hourly excretion of PGF_2α MUM (μg/hour) increased significantly from pregnancy levels to 1.06 ± 0.45 in the first stage (P < 0.01), to 7.67 ± 4.31 (P < 0.005) for the first 2 hours after delivery, and 2.37 ± 1.08 from 2 to 12 hours after delivery (P < 0.01). The excretion of PGF_2α MUM decreased to pregnancy levels 12 hours post partum. These data indicate that during labor the production of PGF_2α is remarkably increased.