Variations in the Maternal Serum Prolactin Levels during Pregnancy, Labor, and the Puerperium

An estimation of the blood HPr levels in normal nonpregnant women, pregnant women, and puerperal women by the RIA method was carried out.
The results were as follows.
1) Serum HPr of normal nonpregnant women 30 min after at rest at 10 a. m. stood at 11.42±3.38 ng/ml.
2) Serum HPr in normal pregnant women showed a slightly higher level during the early stage of pregnancy compared with normal nonpregnant women, and it increased gradually to about a 7-fold increase during the terminal stage of pregnancy.
3) Serum HPr level during labor increased in some cases and decreased in others, showing no fixed tendency.
4) Serum HPr during the puerperium showed the highest level on the 3rd day of the puerperium, and then gradually decreased to show a level close to that of normal nonpregnant women on the 30th day of the puerperium.
5) Regarding the variations in serum HPr before and after breast massage in normal nonpregnant women, pregnant women and puerperal women, the HPr levels showed significant increases after breast massage and the increase rate was the highest in women on the 5th day of the puerperium.
6) In puerperal women on the let 1st and 7th day of the puerperium showing high levels in serum HPr, diurnal variations in their HPr were observed as in nonpregnant normal women; the HPr levels tended to be higher at night than at daytime,showing the increase rates of about 100 to 400 per cent.