Pregnancy-associated risk factors and incidence of systemic sclerosis in primiparous women: A nationwide population-based cohort study.

Objectives: To evaluate the pregnancy-related risk factors and incidence rate (IR) of systemic sclerosis (SSc) in primipara using the Health Insurance Review and Assessment database, covering all medical claims in South Korea.
Methods: From the database, 2,260,952 primipara aged 18-49 years from 2008 to 2018 were identified. The patients were followed up after their index delivery until December 2019. A Cox proportional hazard analysis was performed to identify the association of pregnancy-related factors with SSc development.
Results: The SSc IR was 0.62 cases per 100,000 patient-years. Primipara had a higher risk of developing SSc after 3 years postpartum than in the first 3 years of delivery (OR = 1.98, 95% CI: 1.36-2.78, p < .001). A multivariate analysis showed that older age (35-49 years) (HR = 2.14, 95% CI: 1.05-4.35, p = .037) and a Caesarean section (CS) (HR = 1.86, 95% CI: 1.10-3.15, p = .021) are risk factors for SSc. At 3 years postpartum, CS (HR = 2.97, 95% CI: 1.39-6.32, p = .005) and a female infant (HR = 2.28, 95% CI: 1.11-4.71, p = .026) were associated with SSc development.
Conclusion: Having a CS, late childbirth, and a female infant are the risk factors for SSc in primipara. This study establishes the IR of SSc in primipara.
(© 2021 Japan College of Rheumatology.)