[Melatonin levels in maternal plasma before and during delivery, and in fetal and neonatal plasma]

In the present study, in order to clarify the diurnal changes in pregnant women, fetuses and neonates, pineal hormone (melatonin) was analyzed with a RIA Kit.

1. The venous melatonin concentration at night was higher than during the day in healthy women and full term pregnant women without labor. 2. Melatonin concentrations in maternal venous blood (MV) (67.44 pg/ml) were significantly higher than in umbilical venous blood (UV) (37.78 pg/ml). 3. A distinct midnight peak of melatonin was observed in MV, and UV at delivery. 4. Significant correlations were observed between MV, UV or umbilical arterial blood (UA), but those were non linear. 5. In neonates on the first to fourth day after birth, no midnight peak was able to be clearly observed, but fluctuations were observed. These result indicate that there is a diurnal change in melatonin in full term pregnant women without labor and women in labor. And we suggest that the pineal gland of early neonates secretes melatonin, but no diurnal change in melatonin is established up to 4th day after birth.