Does the delivery mode affect post-birth neonatal serum C-reactive protein levels? A causal effect analysis

Aim: To determine if the delivery mode has a causal effect on neonatal serum C-reactive protein (CRP) levels. If such a causal effect exists, we aim to quantify its magnitude.

Methods: We investigated the causal effect of the delivery mode on serum CRP levels 6-8 h after delivery, with appropriate statistical tools for retrospective studies, combining classical and machine-learning methods. The statistical inference is followed by sensitivity analysis to quantify the magnitude of unobserved bias required in order to alter the study's conclusion.

Results: This retrospective study reviewed laboratory records of neonates after birth who underwent blood tests due to suspected sepsis. A total of 440 newborns were included, 324 of which underwent a vaginal delivery, 59 an urgent caesarean delivery, and 57 an elective caesarean delivery. Our results revealed that serum CRP values following elective caesarean deliveries were 50% less than those following a vaginal delivery (P = 0.030; -0.907; 95% CI [-1.545, -0.268] in log-CRP units). No significant effect was found for urgent caesarean deliveries compared to vaginal deliveries (P = 0.887). Those results were strengthened by (1) a sensitivity magnitude of 1.6 to unobserved bias and (2) non-significant effects when analysis is repeated on blood collected 12-24 h after birth.

Conclusion: CRP concentrations in neonatal blood during the first 6-8 h of life are higher following vaginal deliveries compared to elective caesarean deliveries. Further studies with the intent of improving EONS detection should include information on the delivery mode.