(946) Cesarean section rates and maternity populations at risk: a single center 16 year follow up

Objective: To estimate the association between CS rates and the different maternity populations as classified Robson 10-group Classification (RGC) at a single large maternity center with uniform clinical protocols, between 2005-2021.

Study Design: 235,280 recorded births were categorized using RGC. CS risk was assessed by logistic regressions using both univariate and adjusted multivariate models. All models were re analyzed for parity groups in the RGC, nulliparous and multiparous. Within the nulliparous groups, RG1 was a reference for RG 2a, 2b, 6 and 8-10, and for multiparous, RG 3 was a reference for RG 4, 5, 7 and 8-10).

Results: CS rate increased from 11.0% to 13.8% during the study period (Figure). The largest groups were nulliparous and multiparous women with single cephalic, spontaneous labor at term (RG1 and RG3, respectively); 71.1%. The group that contributed the most to overall CS rate was RG 5 (multiparous, single cephalic pregnancy at term with prior CS), 33.6% of CS. RG5 also had the highest risk among the multiparous analysis (aOR=45.2, 95% CI: 42.5-48.0). Apart from malpresentations, the groups with the highest risk for CS were RG8 (all multifetal pregnancies at any gestational age) overall and among nulliparous women (aOR=6.1 95% CI: 5.4-6.8, and aOR=24.7 95% CI: 20.4-29.8, respectively). Notably, labor induction increased the risk for CS in both nulliparous and multiparous (aOR=3.5 95% CI: 3.5-4.0, and aOR=3.7 95% CI: 3.2-3.9, respectively). (Table)

Conclusion: CS rates are still rising, even in populations with a basic low rate. Interventions to reduce CS rates should be focused on decreasing multifetal pregnancies rate in the setting of assisted reproduction and a careful revision of the limited trial of labor after cesarean. Labor induction was shown to increase the risk for CS in both nulliparous and multiparous groups, warranting inspection of this rising practice.