The association between active proliferative lupus nephritis during pregnancy and small for gestational age newborns

To analyse maternal variables associated with occurrence of small for gestational age (SGA) newborns in pregnancies of women with systemic lupus erythematosus (SLE), considering clinical and laboratory characteristics prior to conception, during gestation and comorbidities.

Retrospective cohort study with SLE pregnant patients and singleton deliveries after 22 weeks. SGA newborn was defined as birth weight below 10th percentile and SLE activity at conception and during gestation was measured using the SLE Pregnancy Disease Activity Index (SLEPDAI). Univariate analysis was employed to evaluate individual influence of demographic and clinical variables on the SGA newborn outcome, while variables with p<0.20 were included in multivariate regression.

Among 151 pregnancies, 28 (18.5%) had SGA newborns. History of proliferative nephritis (RR=3.84, CI 1.63-9.3) and positivity for anti-RNP and anti-Sm antibodies (RR=2.67, CI 1.11-6.43; 2.78, CI 1.44-5.32) were more frequent in the study group. Active proliferative nephritis at conception (RR=3.29, CI 1.75-6.18) and during gestation (RR=3.63, CI 1.97-6.71), as well as complement C3 consumption (RR=2.70, CI 1.09-6.67) and venous pulse therapy with methylprednisolone (RR=20.3, CI 2.18-190), were also associated with SGA newborns, the latter being independently associated in multivariate regression. Adverse perinatal outcomes, such as stillbirths (4.3 times) and neonatal intensive care unit admissions (3.2 times), were more frequent among SGA infants.

Active proliferative lupus nephritis during pregnancy was associated with SGA newborns, while its treatment with venous pulse therapy with methylprednisolone may play a significant role in this context. Presence of previous proliferative nephritis, SLEPDAI ≥4, C3 consumption and presence of anti-RNP and anti-Sm antibodies were additional variables associated with SGA newborns in this population.