Skeletal remodeling of the pelvis and the obstetric risks of advanced maternal age

Advanced maternal age pregnancies are associated with a higher rate of cesarean sections (c-sections). As surgical procedures, c-sections increase the risk of maternal morbidity and mortality. Some have suggested that the increase in c-sections with maternal age reflects an age-related increase in feto-pelvic inadequacy. Here we evaluated whether maternal pelvic remodeling with respect to age and parity explains the increase in c-sections with age. We examined CT scans of recently deceased American individuals from the New Mexico Decedent Image Database (N = 299). The sample was subdivided for sex (male, female), age (15-34 years, 35-50 years, ≥51 years), and parity (parous, nulliparous). We took four obstetrically relevant measurements: anteroposterior (AP) inlet, AP outlet, mediolateral (ML) inlet, and ML midplane. Statistical analyses included the Welch Test to compare the age groups and the Wilcoxon-Mann-Whitney test to compare parity groups. Our results revealed that the only significant age-related differences were for the two mediolateral pelvic canal measurements in females, where individuals ≥51 years old (likely post-menopausal) had wider pelvic canals than the younger individuals, including those who would be considered advanced maternal age (≥35 years). The only parity-related difference was in the AP outlet, which was wider in parous individuals. There were no significant age-related differences in the male sample. We conclude that age-related pelvic remodeling is unlikely to be the reason for the higher incidence of c-sections in advanced maternal age individuals. Why the female pelvic canal expands mediolaterally post-menopause and anteroposteriorly after childbirth both require further exploration.