Maternal Age and Elective Cesarean Section in a Low‐risk Population

Objective. To examine the association between maternal age and elective cesarean section in primiparous and para one women in a low‐risk population. Design. Population‐based registry study. Setting. Norway. Population. The source population was all mothers giving birth to their first or second child from 1 January 1999 to 31 December 2006. The final study population comprised 229 370 primiparous and para one low‐risk mothers. Methods. Data were extracted from the Medical Birth Registry of Norway. We constructed a low‐risk population by excluding pregnancies with medical conditions associated with elective cesarean section and maternal age. The association between maternal age and elective cesarean was analysed by relative‐risk models. Main outcome measures. Elective cesarean section. Results. In this low‐risk population, the proportion of cesarean section was 9%, and 27% of these were elective. Cesarean delivery increased substantially with increasing maternal age, especially elective cesarean section. In primipara, elective cesarean section increased from 0.6 to 7.5% of all deliveries, corresponding to a relative risk of 11.7 (95% confidence interval 8.9–15.4) in women ≥40 years relative to 20–24 years. When comparing women ≥40 years with those aged below 25 years, the relative risk in para one without previous cesarean section was 4.5 (95% confidence interval 3.5–5.8; the proportion increasing from 1.4 to 6.2%), while in para one with previous cesarean section it was 2.9 (95% confidence interval 2.4–3.6; the proportion increasing from 17.5 to 51.5%). Conclusions. We found a close association between maternal age and elective cesarean section in a low‐risk population.