Maternal juvenile rheumatoid arthritis may be associated with preterm birth but not poor fetal growth

Adverse pregnancy outcomes in mothers with juvenile rheumatoid arthritis (JRA) are not known. The objective of this study was to examine the risk of preterm birth and restricted fetal growth in pregnant mothers diagnosed with JRA, and to examine the impact of race/ethnicity and maternal age on this association.

Hospital discharge records for mothers who gave birth in 2011 and 2012 were examined in the National Inpatient Sample (NIS) database. JRA, preterm birth (<37 weeks of gestation), birth weight that is small for gestational age (SGA) and other demographic and clinical variables were identified using ICD-9 (International Classification of Disease--9th revision) diagnostic codes. The associations of JRA with preterm birth and restricted fetal growth were examined controlling for confounding variables.

The sample included 8,273,987 birthing mothers, of these 1236 (0.01%) had JRA. The prevalence of preterm birth and SGA was 6.08% and 2.34%, respectively. Preterm birth in mothers with JRA was 12.9% compared with 6.1% in mothers without JRA with an adjusted odds ratio (OR) of 2.1 (confidence interval (CI): 1.74 to 2.42, P<0.001). The incidence of SGA in infants born to mothers with JRA was 3.34% compared with 2.34% in non-JRA mothers, which was not statistically significant. Adjusted OR for preterm birth in association with JRA among White mothers was 1.78 (CI: 1.41 to 2.24, P<0.001). However, Hispanic mothers with JRA (12%) were the ethnicity to suffer the most from preterm birth with an adjusted OR of 4.43 (CI: 2.97 to 6.62, P<0.001). Preterm birth among advanced maternal age (AMA) mothers with JRA was 25% compared with 7% in those without JRA with an adjusted OR of 5.42 (CI: 3.51 to 8.35, P<0.001).

JRA is associated with preterm birth but not with SGA. This association is significantly influenced by race/ethnicity and maternal age. More studies are needed to examine these findings in relation to medications used, severity of the disease and exacerbation during pregnancy to understand the genetic/socioeconomic factors behind these racial/ethnic differences.