medwireNews: Tumor necrosis factor (TNF) inhibitor use by pregnant women with well-controlled rheumatoid arthritis (RA) is associated with a reduced risk for having a child that is born small for gestational age (SGA), study findings indicate.
“Future research should focus on understanding the underlying mechanism of TNF-inhibition on birth weight and the long-term consequences for the offspring,” write Hieronymus Smeele and colleagues, from Erasmus MC in Rotterdam, the Netherlands, in the Annals of the Rheumatic Diseases.
The analysis included data for 188 women from the Preconception Counseling in Active RA study who were treated according to a protocol that targeted minimal disease activity. Of these, 48.9% used a TNF inhibitor during pregnancy.
DAS28-CRP in the full cohort was low at all timepoints during pregnancy, with mean first, second, and third trimester scores of 2.21, 2.30, and 2.17 points, respectively. The corresponding values among those who used a TNF inhibitor were 2.18, 2.35, and 2.22 points.
Smeele and team report that women who used a TNF inhibitor had significantly heavier babies, on average, than those who did not (3.344 vs 3.171 kg) and were significantly less likely to have a baby that was SGA (<10th percentile; 9.8 vs 20.0%) or require an emergency cesarean section (6.9 vs 50.0%).
There was no significant difference between the two groups in the rates of pre-eclampsia (5.4 vs 6.3%), gestational hypertension (4.4 vs 8.3%), congenital malformations (7.6 vs 6.3%), or babies born large for gestational age (>90th percentile; 7.6 vs 6.3%).
In multivariate analysis adjusted for potential confounders, maternal age was significantly and negatively associated with birthweight, whereas there were significant positive associations between birthweight and TNF inhibitor use, diabetes mellitus, and gestational age.
Focusing on TNF inhibitor use, Smeele et al observed that the association with birthweight was stronger when the drugs were used later in pregnancy. Specifically, the babies of mothers who used a TNF inhibitor during the first trimester were, on average, a nonsignificant 90.6 g heavier than the babies of mothers who did not use a TNF inhibitor. This difference increased to a significant 180.5 g and 191.5 g with TNF inhibitor use in the second and third trimesters, respectively.
However, the investigators say that this finding should be “interpreted with caution” because women who used a TNF inhibitor in the third trimester were most likely to have used them in the first and second trimesters as well.
The authors conclude that theirs is the first study “to show a strong association between TNF [inhibitor] use during pregnancy and an increased birth weight of the offspring when corrected for major confounders.”
They add that “TNF [inhibitors] might be a future therapeutic option in preventing and treatment of intrauterine growth restriction.”
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