Late gestational maternal serum cortisol is inversely associated with fetal brain growth.

To analyze the association between fetal brain growth and late gestational blood serum cortisol in normal pregnancy.Blood total cortisol was quantified at delivery in 432 Chinese mother/child pairs. Key inclusion criteria of the cohort were: no structural anomalies of the newborn, singleton pregnancy, no alcohol abuse, no drug abuse or history of smoking no hypertensive disorders and no impairment of glucose tolerance and no use of steroid medication during pregnancy. Differential ultrasound examination of the fetal body was done in early (gestational day 89.95 ± 7.31), middle (gestational day 160.17 ± 16.12) and late pregnancy (gestational day 268.89 ± 12.42). Newborn's cortisol was not correlated with any of the ultrasound measurements during pregnancy nor with birth weight. Multivariable regression analysis, considering timing of the ultrasound examination, the child's sex, maternal BMI, maternal age, maternal body weight at delivery, the timing of cortisol measurement and maternal uterine contraction states, revealed that maternal serum total cortisol was significantly negative correlated with ultrasound parameters describing the fetal brain: late biparietal diameter (R²=0.512, p=0.009), late head circumference (R²=0.498, p=0.001), middle biparietal diameter (R²=0.819, p=0.013), middle cerebellum transverse diameter R²=0.76, p=0.014) and early biparietal diameter(R²=0.819, p=0.013). The same analysis revealed that birth weight as well as ultrasound parameters such as abdominal circumference and femur length were not correlated to maternal cortisol levels. In conclusion, our study demonstrates that maternal cortisol secretion within physiological ranges may be inversely correlated to fetal brain growth but not to birth weight. It remains to be demonstrated whether maternal cortisol secretion negatively influencing fetal brain growth translates to adverse neurological outcomes in later life.