Simultaneous determinations of total cortisol and progesterone by radioimmunoassay during late pregnancy.

Total cortisol and progesterone in the maternal peripheral sera were determined by radioimmunoassay. Total cortisol was measured in 196 sera, and progesterone in 203 sera obtained randomly throughout pregnancy. And serial estimations of both steroid hormone levels were also made simultaneously in 6 normal pregnant women during late pregnancy, labour and puerperium. Total cortisol and progesterone increased with the advance of gestation. During the last few weeks preceding labour total cortisol increased further, whereas progesterone decreased. After the onset of labour a rising tendency in total cortisol levels and a falling tendency in those of progesterone were also observed, but at puerperium both hormones decreased rapidly to non-pregnant level in the 6 pregnant women.