Why the caesarean section rate is high in women with ankylosing spondylitis: Using the Korean National Health Insurance database.

Objective. Women with ankylosing spondylitis (AS) have reported a higher rate of cesarean births than healthy controls. This study aimed to identify factors associated with cesarean births in women with AS. Methods. Based on the Korean Health Insurance Review and Assessment Service claims database, the subjects comprised female patients aged 20-49 years old with AS. In total, 1293 deliveries after AS diagnosis were included. A logistic regression analysis was performed to identify factors associated with cesarean births. Results. Among the 1293 deliveries in women with AS, 657 were cesarean and 636 were vaginal deliveries. Compared to vaginal delivery, the women who had cesarean deliveries were older, had a longer disease duration, and had a higher portion of primipara and dispensation of drugs. These factors were associated with a higher risk of cesarean delivery: maternal age (OR 1.08, 95% CI 1.04-1.12), disease duration (OR 1.09, 95% CI 1.03-1.14), and preeclampsia (OR 3.94, 95% CI 1.17-13.32). Further, compared to no drug dispensation, these drugs showed higher risks of cesarean delivery: nonsteroidal antiinflammatory drugs (NSAID; OR 1.64, 95% CI 1.31-2.37), tumor necrosis factor inhibitor (TNFi), disease-modifying antirheumatic drugs (DMARD), or corticosteroids (OR 2.01, 95% CI 1.57-2.58). In the subgroup analysis in primiparas, maternal age, or dispensation of NSAID alone, or TNFi, DMARD, or corticosteroids was associated with a higher risk of cesarean delivery. Conclusion. Women with AS showed a higher cesarean delivery rate, influenced by both maternal age and disease-related factors.