Objective: SLE is prevalent among women of reproductive age, increasing the risk of adverse pregnancy outcomes (APOs). However, the correlation between the onset time of SLE and APOs remains unclear. This study aimed to analyse and compare pregnancy outcomes and clinical characteristics among three groups of patients with SLE: those with childhood onset, onset in adulthood before pregnancy and onset in adulthood during pregnancy.

Methods: A retrospective analysis was conducted on pregnant women with SLE admitted to Nanfang Hospital of Southern Medical University from 2010 to 2024. Patients were categorised based on the onset time of SLE. Clinical features, laboratory characteristics, medication and pregnancy outcomes were compared among three groups. Logistic regression analyses were used to explore the relationship between the onset time of SLE and APOs.

Results: The study included a total of 251 pregnancies from 223 women. Pregnant women with SLE onset in adulthood during pregnancy had more pronounced multisystem disorders, higher disease activity and an increased incidence of APOs. SLE onset in adulthood during pregnancy was associated with a higher risk of fetal loss (OR=5.342, 95% CI 1.629 to 17.520, p=0.006) and premature birth (OR=6.390, 95% CI 1.244 to 32.828, p=0.026).

Conclusions: Patients with SLE onset in adulthood during pregnancy exhibit more aggressive disease manifestations and higher rates of APOs, while women with childhood-onset or pre-pregnancy-onset SLE had a lower risk. The incidence of APOs does not correlate with disease duration if maternal disease is quiescent in the period before conception. Closer monitoring and tailored management strategies are needed for these patients.