Women with inflammatory polyarthritis have babies of lower birth weight

Objective. To assess the effect on fetal outcome, and development of the ch ild over the first 8 months of life, of rheumatoid arthritis (RA) during pr egnancy. Methods. Women with RA or undifferentiated inflammatory polyarthritis (IP) were recruited from throughout the UK and followed prospectively from late pregnancy to 8 months postpartum. Matched controls were obtained from gener al practitioners. The babies' health at birth and development at 8 months w ere monitored by the weight, head circumference, and length, Potential conf ounding variables were noted. Results. One hundred thirty-three women with RA or undifferentiated IP took part in the study. There were 5 (4%) admissions for hypertension during pr egnancy and no cases of preeclampsia. Cesarean section was common (23%). Ma tched controls were found for 103 (77%) subjects. There were no significant differences between groups in head circumference or length at birth. Babie s born to women with arthritis had lower mean birth weight than controls [3 .3 kg (standard deviation 0.5) compared to 3.5 kg (0.4); p = 0.004], even a fter adjustment for potential confounding factors. Within the patient group those whose arthritis was in remission had significantly heavier babies th an those with active disease [mean 3.5 kg (0.5) compared with 3.3 kg (0.5); p = 0.04]. This trend was still apparent at 8 months, but differences were no longer statistically significant. Conclusion. This is the first relatively large prospective study of the eff ects on mother and baby of RA during pregnancy. The results suggest that, a lthough disease improves in most women during pregnancy, it is still suffic iently active to have a modest negative effect on birth weight.