Rheumatoid arthritis and birth outcomes: a Danish and Swedish nationwide prevalence study

To examine the prevalence of preterm birth, infants with low Apgar score, small for gestational age (SGA) birth, stillbirth and congenital abnormalities in women with rheumatoid arthritis (RA) compared with women without RA.

Prevalence study.

Combined Sweden and Denmark nationwide from 1994 to 2006.

We included 871,579 women with a first-time singleton birth identified through population-based healthcare databases.

We compared the prevalence of preterm birth, low Apgar score (<7 at 5 min), SGA birth, stillbirth and congenital abnormalities amongst women with RA compared with women without RA using prevalence odds ratio (OR) with 95% confidence interval (95% CI), whilst controlling for maternal age, smoking, parental cohabitation and year. We stratified analyses by period of birth (1994-1997, 1998-2001 and 2002-2006).

Amongst 1199 women with RA, 7.8% gave birth between 32 and 36 gestational weeks (adjusted OR, 1.44; 95% CI, 1.14-1.82), 1.4% gave birth before gestational week 32 (adjusted OR, 1.55; 95% CI, 0.97-2.47), 1.6% had an infant with a low Apgar score (OR, 0.99; 95% CI, 0.95-1.65), 5.9% had an SGA birth (adjusted OR, 1.56; 95% CI, 1.2-2.01), 0.9% experienced stillbirth (adjusted OR, 2.07; 95% CI, 0.98-4.35) and 4.3% gave birth to an infant with congenital abnormalities (adjusted OR,1.32; 95% CI, 0.98-1.79). The OR for congenital abnormalities decreased from 2.57 (95% CI, 1.59-4.16) in 1994-1997 to 1.00 (95% CI, 0.64-1.56) in 2002-2006.

Women with RA had a high prevalence of most adverse birth outcomes. This could be due to inflammatory activity, medical treatment or other factors not controlled for.