Trends in cesarean birth rates in Iceland over a 19-year period

Background Cesarean birth (CB) rates have increased in high-resource countries during the past two decades, yet it is not known whether CB rates have changed according to maternal age and/or gestational age. Methods All singleton live births in Iceland between 1997 and 2015 were identified from the Icelandic Medical Birth Registry (80 130). Rates of cesarean births (intrapartum and prelabor) were calculated overall and separately for maternal age groups and gestational age groups and by parity. Logit binomial regression was used to calculate odds ratios (ORs) and confidence intervals (CIs) for annual change in cesarean birth rates adjusted for maternal characteristics and clinical indication groups. Results The overall CB rate was 15.7% in 1997 and 15.8% in 2015; the CB rate did not change significantly during the study period. The overall CB rate for early-term deliveries (37-38 weeks) decreased for multiparas (annual aOR = 0.99 [95% CI = 0.98-0.99]), and the preterm (<37 weeks) prelabor cesarean rate increased significantly (1.11 [1.09-1.14]) for both primiparas and multiparas. For multiparas only, the intrapartum CB rate decreased (0.97 [0.97-0.98]), whereas the prelabor CB rate increased, predominantly for women aged over 35 years (1.03 [1.02-1.04]). Adjustment for clinical indication groups did not change these results. Conclusions Findings indicate a rise in prelabor cesarean for preterm births and women aged over 35 years (multiparas only). As adjustment for clinical indications did not affect these results, changes in obstetric practice are more likely to have affected these rate changes rather than changes in clinical indications.