Long-term developmental outcomes of method of delivery.
OBJECTIVE: In the general framework of relating birthing events to later mental development, this study addresses the hypothesis that uneventful non-vertex delivery is associated with higher intelligence than uneventful vertex delivery. STUDY DESIGN: In the course of a developmental obstetrical survey, data was gathered prospectively on families having a non-vertex birth at Huron Road Hospital during the 1950s and early 1960s. The intelligence quotient (IQ) scores and school success ratings for the cohort of 658 children who had been delivered uneventfully by specific non-vertex methods of birth (viz. elective section, breech and internal podalic version) are compared with those of 1151 of their own siblings and peers delivered by cephalic presentation without complication. Intrafamily comparisons allow the control of genetic and socioeconomic factors. RESULTS: The one-sided 95% confidence intervals (using the t-statistic) for mean values do not overlap. They are: IQ > 112.1 (non-vertex) vs. < 110.1 (vertex) and school success scores > 2.64 (non-vertex) vs. < 2.54 (vertex). These findings are confirmed for IQ when the analysis is restricted to only those 434 children in the families allowing intrafamily comparisons (i.e. comparable siblings born by both non-vertex and vertex deliveries). The one-sided 95% confidence intervals for mean values do not overlap. They are: IQ > 112.89 (non-vertex) vs. < 112.86 (vertex). CONCLUSIONS: Speculation is given as to the reasons for this phenomenon. It is unclear whether these differences are due to physical phenomena related to delivery or to effects due to differing levels of anesthesia-analgesia or whether these differences in intellectual potential are associated with the cause of obstetrical difficulties.