between days 17 and 20 of pregnancy , serum concentrations of progesterone declined from 130 +/- 3 to 80 +/- 3 ng/ml , while 20 alpha-hydroxypregn-4-en-3-one ( 20 alpha-oh-p ) concentrations declined from 34 +/- 3 to 18.5 +/- 3 ng/ml .
C0032961
pregnancy
C0033308
progesterone