Umbilical cortisol levels as an indicator of the fetal stress response to assisted vaginal delivery

Abstract

Objectives: While it is well established that delivery by elective caesarean section is less stressful for the fetus than normal vaginal delivery, little attention has been paid to the effect on the baby of an assisted delivery. Study design: We examined cortisol levels in venous cord blood from seven babies born by forceps, 10 by ventouse extraction, 28 by unassisted normal vaginal delivery, and 12 born by elective caesarean. Paired maternal bloods were taken immediately after delivery. Results: Cord blood cortisol values were significantly different in the different groups (one-way ANOVA, P<0.0001). The forceps group had the highest values and the caesarean group the lowest; both were different from the normal vaginal delivery group ( P=0.019 and P=0.046, respectively). There was no effect of length of labour, or method of pain relief on cortisol levels. Maternal values were similar in the different groups, confirming that the differences observed derived from the fetus. Conclusions: There is increasing evidence that the stress experienced by the fetus or neonate can have long-term effects on the function of the hypothalamic–pituitary–adrenal axis in later life. We speculate that the stress caused by some assisted deliveries may contribute to this.