Women with systemic lupus erythematosus get pregnant more easily than women with rheumatoid arthritis.

Objectives: To examine possible differences in the ability to get pregnant and time to pregnancy (TTP) in women with SLE and RA, and to study possible influencing factors.

Methods: Data from RevNatus, a Norwegian nationwide prospective observational register including women with inflammatory rheumatic diseases when planning pregnancy or after conception, was used. We compared rate of achieved pregnancy, the pregnancy outcomes live birth or pregnancy loss, and TTP between women with SLE (n = 53) and women with RA (n = 180). TTP was compared between the groups using Kaplan-Meier plots, and Cox proportional hazard regression was performed adjusting for maternal age, parity and medication use. RAND-36 was used to assess health-related quality of life (HRQoL) in women achieving and not achieving pregnancy.

Results: Women with SLE had a pregnancy ratio of 1.91 (95% CI: 1.27, 2.88, P = 0.002) compared with women with RA, and a substantially shorter median TTP (3.0 vs 7.0 months, P = 0.001). Higher maternal age, medication use and low HRQoL in the physical domains may influence the ability to achieve pregnancy and prolong TTP in women with RA. Women with SLE not achieving pregnancy had lower HRQoL scores than SLE-women achieving pregnancy, while women with RA had generally low scores in physical domains whether or not achieving pregnancy, indicating poor HRQoL.

Conclusions: In the studied cohort, women with SLE got pregnant more easily than women with RA.