Plasma cortisol levels in human fetus during parturition

Area of Science:

• Endocrinology
• Obstetrics
• Perinatology

Background:

• The fetal adrenal cortex is implicated in labor onset in some mammals.
• Evidence for its role in human labor initiation is inconclusive.
• Previous studies on cord blood cortisol levels are limited by timing.

Purpose of the Study:

• To investigate the role of the fetal adrenal cortex in initiating human labor.
• To determine if fetal cortisol levels change before or during labor.
• To assess the validity of cord blood cortisol for prelabor estimation.

Main Methods:

• Sequential fetal scalp blood sampling during spontaneous and induced labor.
• Comparison of fetal cortisol levels across labor onset types.
• Analysis of maternal and fetal blood cortisol during labor.
• Comparison with cord blood cortisol in elective cesarean sections.

Main Results:

• Initial fetal cortisol levels were similar regardless of labor onset type.
• A significant rise in plasma cortisol occurred in both maternal and fetal blood during labor.
• These findings do not support fetal adrenal cortex involvement in labor initiation.

Conclusions:

• The fetal adrenal cortex likely does not initiate human labor.
• Cord blood cortisol levels are unreliable for estimating prelabor fetal cortisol.
• The cortisol surge during labor may reflect maternal stress response.