Background Women with systemic lupus erythematosus (SLE) have an increased risk of delivering preterm and low birthweight infants. In the general population, maternal obesity is associated with an increased risk of preterm birth and lower risk for small for gestational age (SGA) infants. The effect of maternal obesity on birth outcomes among SLE patients is unknown.
Objectives To estimate the association of pre-pregnancy body mass index (BMI) among women with SLE on preterm birth and birthweight for gestational age percentiles in live born infants.
Methods We used data prospectively collected in the Hopkins Lupus Pregnancy Cohort from 1987-2011 (n=450 pregnancies). Our analysis sample was restricted to SLE patients with a maternal weight measurement within one year prior to pregnancy or during the first trimester (n=216). Outcomes of interest were preterm birth (<37 weeks gestation), infants born small for gestational age (SGA; birthweight <10th percentile for gestational age), and birthweight for gestational age percentiles. BMI was categorized as underweight or normal weight (<25 kg/m2), overweight (25-29.9 kg/m2) and obese (≥30 kg/m2). Data were analyzed by ANOVA and logistic regression models. Race and prednisone use ever during pregnancy were included as a covariates in all models.
Results Of the 216 eligible pregnancies who had a pre-pregnancy weight available in the eligible time frame, patients were 59% white, 32% black, had a median age of 29.2 years, a median disease duration of 5.1 years and a median highest physician global assessment of disease activity (PGA) score during pregnancy of 1.0 (range: 0-2.5). There were 68 preterm births (32%), and the median birthweight percentile was 31.5 (19% SGA of 202 live births). The majority of women were underweight or normal weight (56%), 24% were overweight and 20% were obese. The frequency of preterm birth was 32% for underweight/normal weight women, 41% for overweight women and 18% for obese women. The exact odds ratio (OR) for preterm birth for overweight and obese women compared to underweight and normal weight women was 1.1 (95% CI: 0.6-2.2), adjusted for race and prednisone use. Adjustment for disease activity did not affect the results. The frequency of SGA was 23% for underweight/normal weight women, 11% for overweight women and 19% for obese women. The exact OR for SGA for overweight and obese women compared to underweight and normal weight women was 0.6 (95% CI: 0.3-1.4), adjusted for race and prednisone use during pregnancy. Adjustment for disease activity did not affect the results. The mean birthweight for gestational age percentile was lower for women classified as underweight/normal weight (31.0±23.6 vs. 44.4±27.0 in overweight and 37.6±29.9 in obese).
Conclusions While pre-pregnancy BMI was not significantly associated with preterm birth or SGA, our results suggest that, although the precision of the estimate is limited due to the small sample, being overweight and obese may potentially be protective against SGA, which is similar to what is seen in the general population.
Disclosure of Interest None declared