BELLEVUE, WASH. – The severity of rheumatoid arthritis early in pregnancy is an independent risk factor for preterm delivery, according to data from the Organization of Teratology Information Specialists Autoimmune Diseases in Pregnancy Project.
The prospective cohort study of 447 pregnant women with rheumatoid arthritis who had a live-born infant from 2005-2013 found that the greater disease severity before 20 weeks of gestation, assessed by a variety of measures, the higher the adjusted risk of delivering preterm. But there was no significant impact on the adjusted risk of having an infant small for gestational age or a cesarean section.
"Disease severity in women with rheumatoid arthritis, measured early in pregnancy, is predictive of preterm delivery," noted Dr. Balambal Bharti, a researcher at the bioscience center, University of California, San Diego, in presenting the findings at the annual meeting of the Teratology Society.
The investigators are performing additional analyses to determine whether disease severity at different times – early versus late pregnancy – has a similar or differing impact, and to assess any effect of a change in severity during pregnancy.
"For future research, we’d like to investigate if better disease management early in pregnancy improves pregnancy outcome," she said.
Session cochair Suzan L. Carmichael, Ph.D., of the department of pediatrics (neonatology) at Stanford (Calif.) University asked, "Did you know if there were differences in disease severity or treatment based on whether women had planned their pregnancies, and whether that could have affected your results? I’m just wondering if there are certain women who had planned their pregnancy and had changed their treatment regimen in anticipation of that."
"We didn’t know whether women had planned their pregnancies," Dr. Bharti replied, although some data suggest that about half of pregnancies in the Organization of Teratology Information Specialists cohort are unplanned. The investigators also did not look at whether women changed their treatment before conceiving, she said.
Session attendee Dr. Jan M. Freidman of the University of British Columbia in Vancouver noted, "Two of the three outcome variables you looked at are actually continuous variables: birth weight (or birth weight for gestational age) and week of gestation at which you deliver. As a clinician, it would be useful to know what the size of the effect was in terms of those continuous variables: How much did [disease severity] reduce birth weight? How much was the reduction, or was there a reduction, in gestational age? Did you look at the analysis in that way, or just in the discrete way you presented here?"
"All of our outcomes were dichotomized," Dr. Bharti replied.
"There is more information there that you might want to look at," Dr. Friedman recommended.
The women studied were administered the 4-point Health Assessment Questionnaire Disability Index (HAQ-DI) at baseline, before 20 weeks of gestation. They also rated their pain and global health in the past week on 100-point scales.
Overall, 15% of the women had a preterm delivery (one occurring before 37 weeks of gestation), 9% gave birth to an infant who was small for gestational age, and 42% had a cesarean section.
In multivariate adjusted analyses, women’s risk of preterm birth rose with each 1% increase (worsening) in HAQ-DI score (relative risk, 1.55) and with each 20-point increase (worsening) in pain score (RR, 1.17) and score on the global scale of overall health (RR,1.22).
In contrast, none of the three measures of disease severity independently predicted small for gestational age or cesarean delivery.
Dr. Bharti said that, to the authors’ knowledge, only one other prospective study has looked at the impact of rheumatoid arthritis disease severity on pregnancy outcomes (Arthritis Rheum. 2009;60:3196-206). That study followed white Dutch-speaking women in a first pregnancy who were taking prednisone, sulfasalazine, or hydroxychloroquine.
"Our study adds to [that study] by having women of diverse ethnic background who were in a first or subsequent pregnancy, and they were either on no treatment for rheumatoid arthritis or on any kind of treatment," she commented.
The new findings are generally similar to those of that previous study but differ in that they show a positive association between disease severity and preterm delivery, according to Dr. Bharti.
She disclosed no conflicts of interest related to the research.