The activity of the hypothalamo-pituitary adrenal axis was examined, by measuring the levels of immunoreactive (IR) corticotropin-releasing hormone (CRH), adrenocorticotropin (ACTH) and cortisol (F) in human plasma during normal pregnancy and after delivery with or without complications and during normal postpartum using a specific RIA. The level of IR-CRH in maternal plasma increased progressively during pregnancy, increased further at delivery and declined rapidly to the non-pregnant level on the 1st day postpartum. The level of IR-F in maternal plasma also increased progressively during pregnancy, increased further at delivery, but decreased slowly postpartum, not returning to the non-pregnant level within 5 days. Significant correlations were found between the level of IR-CRH and IR-ACTH, IR-CRH and IR-F, and IR-ACTH and IRF in maternal plasma both during pregnancy and after delivery. It is noteworthy that the concentration of IR-CRH in the maternal plasma at delivery was higher in multiple pregnancy than in normal pregnancy, and that the level of IR-CRH in the umbilical cord in uncomplicated cases was much lower than that in the maternal plasma, and was significantly lower than those in the umbilical cord plasma in cases of asphyxia, IUGR or premature delivery. The level of IR-F, not IR-CRH and IR-ACTH, at normal vaginal delivery was significantly higher than that at elective cesarean section. On these results, we investigated the feto-maternal-hypothalamo-pituitary adrenal axis during pregnancy and delivery, in which CRH plays an important role.

Maternal plasma concentrations of immunoreactive endothelin (ir-ET) during pregnancy, labour and after birth were measured by radioimmunoassay. Concentrations of ir-ET in the umbilical artery, umbilical vein, amniotic fluid and neonatal urine were also examined. The mean (+/- S.E.M.) plasma ir-ET concentration in early pregnancy (4-7 weeks) was 13.7 +/- 0.5 pmol/l, which was significantly higher than that in non-pregnant women (5.9 +/- 0.3 pmol/l). During pregnancy, plasma ir-ET concentrations gradually decreased to a minimum of 11.5 +/- 0.4 pmol/l in weeks 20-23, and then increased again towards term (12.5 +/- 0.4 pmol/l after 36 weeks of pregnancy). In women undergoing vaginal delivery, the mean plasma ir-ET concentration (17.1 +/- 0.7 pmol/l) increased significantly, compared with that in late pregnancy. After delivery, the plasma ir-ET concentration decreased abruptly to 4.0 +/- 0.2 pmol/l on the first day. Plasma ir-ET concentrations in umbilical vessels were significantly higher than those in maternal plasma. In addition, concentrations in the umbilical artery were significantly higher than those in the umbilical vein in cases of vaginal delivery. Concentrations of ir-ET in amniotic fluid were much higher than those in maternal or fetal plasma. ir-ET concentrations in neonatal urine on day 1 after birth were below the detection limit (less than 0.1 pmol/l) by radioimmunoassay in 70% of the cases examined but on day 5 after birth ir-ET was present at measurable concentrations in all cases. It is suggested that endothelin may act as a circulating hormone during pregnancy and labour in both maternal and fetal circulations.

Changes in concentration of human atrial natriuretic peptide (hANP) in normal and toxaemic pregnancy were examined. The maternal plasma concentration of hANP increased gradually during normal pregnancy to a maximum of 20.0 +/- 2.4 pmol/l (mean +/- S.E.M.) after week 36 of pregnancy. From week 20, the plasma concentrations of hANP were significantly higher than those in non-pregnant women (9.3 +/- 2.0 pmol/l). In toxaemia with hypertension, maternal plasma hANP levels were increased after week 26 of pregnancy (37.7 +/- 6.0 pmol/l) compared with those in normal gravida at the same time (17.1 +/- 1.6 pmol/l). Maternal plasma hANP levels in toxaemia only with oedema were not different from those in normal gravida.

The change in plasma concentration of atrial natriuretic peptide (hANP) at delivery was examined by measuring the concentrations of hANP in plasma samples from 21 subjects after 36 weeks of normal pregnancy, 22 subjects after normal spontaneous delivery and 20 subjects after elective cesarean section. The maternal plasma concentration of hANP after normal delivery (38.0 · 8.2 fmol/ml, mean · S.E.M.) was significantly higher than that after 36 weeks of normal pregnancy (16.8 · 2.3 fmol/ml), but its concentration after cesarean section was not different from that after 36 weeks of pregnancy. After normal delivery, the plasma concentration of hANP in the umbilical artery (66.9 · 11.8 fmol/ml) was also significantly higher than that in the umbilical vein (35.1 · 7.3 fmol/ml). In contrast, after elective cesarean section, the hANP levels in the umbilical artery and vein were not significantly different. These results suggest that hANP secretion into the maternal and fetal circulation may be stimulated by the dynamic movement of the mother in labour and the stress of the fetus at delivery, respectively.

Evaluation of amniotic phospholipids, which are a parameter of fetal lung maturation, is important in the management of premature infants. The method available for measuring the lecithin/sphingomyelin (L/S) ratio, which appears to provide an index to fetal lung maturity, is laborious, involving determinations of phospholipids, and so is unsuitable for rapid quantitative measurement of phospholipids in the amniotic fluid in the perinatal period. We developed a simple, sensitive colorimetric assay for phospholipids without their extraction. This assay is based on the fact that phospholipids form stable hydrophobic complexes with Co(SCN)4, Fe(SCN)2‐ and Fe(SCN)3 within about 1 hr. Amniotic fluid samples (n=115) were collected from women with normal and abnormal pregnancies in week 16–41 of pregnancy, and these samples were examined both by thin layer chromatography (TLC) and by our method of phospholipid determination. Good correlations were observed between the L/S ratio determined by TLC and the values obtained by this method. Moreover the distributions of the dipalmitoylphosphatidylcholine(DPPC) content and DPPC/sphingomyelin(SM) ratio were similar to those of the PC content and L/S ratio. This method was proved to be more accurate than other methods such as TLC and the shake test for predicting neonatal RDS.