Adverse pregnancy outcomes across SLE subgroups: significance of cardiovascular events

SLE is associated with increased risks of maternal cardiovascular events (CVEs) as well as adverse pregnancy outcomes. The influence of maternal CVEs on pregnancy complications in lupus is not clearly known. Our primary aim was to assess the risks of adverse pregnancy outcomes in individuals with SLE, specifically examining the influence of CVEs.

Using a California population-based birth cohort from 2005 to 2020, pregnant individuals with SLE were identified via International Classification of Diseases codes on maternal discharge records and further subdivided based on whether they had lupus nephritis (LN) or antiphospholipid syndrome (APS). We analysed adjusted relative risks (aRRs) of adverse pregnancy outcomes in SLE subgroups, comparing those with and without CVEs, to the reference group of pregnant individuals without autoimmune rheumatic diseases or APS and CVEs. CVEs were broadly defined to encompass thromboembolic and cardiovascular conditions associated with SLE.

CVEs complicated 17 130/7004 334 (0.2%) of pregnancies in individuals without autoimmune rheumatic diseases or APS, and 176/8422 (2.1%) with SLE, including 52/903 (5.8%) with LN and 40/513 (7.8%) with APS. Compared with the reference group, the aRRs for maternal complications were higher in SLE subgroups: non-cardiac severe maternal morbidity (3.2-fold to 31.5-fold), intensive care admission (2.0-fold to 12.2-fold), 1 year re-admission (2.4-fold to 6.0-fold) and death (7.0-fold to 7.9-fold). Similarly, adverse infant outcomes were higher: preterm birth (2.3-fold to 6.8-fold), small-for-gestational-age infant (1.8-fold to 3.4-fold), neonatal intensive care admission (2.1-fold to 7.9-fold) and infant death (1.6-fold to 3.7-fold), with highest risk estimates for SLE with LN or APS, particularly when complicated by CVEs.

LN and APS in SLE contributed to incremental risks for adverse outcomes, with the combination of LN or APS with CVEs yielding the highest point estimates. This underscores the importance of disease severity but also the impact of CVEs, helping to individualise the risks of pregnancy complications for various SLE subpopulations.