Background Mean birthweight is lower in children of SLE-mothers than in references. Active disease in pregnancy is considered one of the risk factors.
Objectives The aim of this study was to explore the association of disease activity in women with SLE in pregnancy and the birth weight of the child expressed as mean birth weight and mean z-score for birth weight.
Methods We linked data from RevNatus with data from the Medical Birth Registry of Norway (MBRN). RevNatus is a Norwegian nationwide prospective observational register including women with an inflammatory rheumatic disease when planning pregnancy or after conception. The register is administered by the National advisory unit on pregnancy and rheumatic diseases. Women 18 years or older are recruited and followed-up in each trimester of pregnancy and at 6 weeks, 6 months and 12 months after birth. MBRN is a national birth registry. The population constituted all singleton live births recorded in MBRN in the period 2006 – 2014. The births in women diagnosed with SLE in MBRN and included in RevNatus formed the patient group (n=180). The references were all other births (n=498849). Mean birth weight in the patient group was compared to mean birth weight in the general obstetric population. We calculated z-score for birth weight adjusted for gestational age and sex. The target population was then split in two groups according to disease activity assessed in the 2nd trimester, and compared to references. One-way ANOVA was performed to compare SLE-women without active disease, SLE-women with active disease and references from the general obstetric population.
Results The mean birth weight and mean z-score were both significantly lower in women with SLE compared to references.
When comparing three groups, a significantly lower mean birth weight and mean z-score remained between women without active disease and references and women with active disease and references. There were no significant differences between the two disease groups.
Conclusions Mean birth weight and Z-score was significantly lower in women with SLE compared to the general obstetric population. There were no significant differences in diseased women with active as opposed to quiescent disease.
Disclosure of Interest None declared