Peripartum prolactin and cortisol level changes. A prospective pilot study

Although the role of prolactin and cortisol in the human lactation process seems to be undisputed, the changes in postpartum serum concentrations in mothers make data interpretation difficult.

To determine the factors that possibly influence these hormones, we examined a group of patients who were admitted to the Gynecology-Obstetrics Clinical Hospital in Poznań for labor induction and/or in the active phase of the first labor period. The serum levels of cortisol and prolactin were assessed in these full-term pregnant women during admission to labor, in the third stage of labor, and on the second day postpartum. The prolactin and cortisol levels were also measured in the umbilical cord for the assessment of newborn babies.

The results showed a significant relationship between maternal age and the level of prolactin measured before childbirth and fluctuations in cortisol level with respect to labor duration. In addition, we observed a strong correlation between the level of prolactin assessed before childbirth and the pH and base excess of the umbilical cord artery. Most importantly, a correlation was noted between breastfeeding within 2 hours after the labor and the level of cortisol measured after childbirth.

We observed a significant correlation between a summarized labor duration and maternal and umbilical cord cortisol levels measured right after the labor. The fact of breastfeeding within 2 hours after the labor strongly correlated with lower levels of maternal cortisol as well as a cortisol level in umbilical cord blood and it suggests that immediate initiation of breastfeeding reduces stress level for both, mother and newborn.