Objective To investigate outcome and course of pregnancies in women with axial spondyloarthritis (axSpA) in a pooled data analysis of pregnancy registries in rheumatology.

Methods Prospectively followed women with axSpA, fulfilling ASAS classification criteria and for whom a pregnancy outcome was reported, were eligible for the analysis. Anonymised data of four registries was pooled. Rates of adverse pregnancy outcomes were calculated. Systemic inflammation, disease activity and treatment patterns with tumour necrosis factor inhibitor (TNFi) before, during and after pregnancy were analysed.

Results In a total of 332 pregnancies from 304 axSpA women, 98.8% of the pregnancies resulted in live birth. Mean maternal age was 31 years and disease duration 5 years. Most of these patients received pre-conception counselling (78.4%). Before pregnancy, 53% received TNFi treatment, 27.5% in first and 21.4% in third trimester. Pregnancy and neonatal outcomes were favourable with rates of 2.2% for pre-eclampsia, 4.9% for preterm birth, 3.1% for low birth weight and 9.5% for small for gestational age. Neonates were delivered by caesarean section in 27.7% of pregnancies, of which 47.4% were emergencies. Pooled mean CRP was 4 mg/L before conception peaking in the second trimester at 9.4 mg/L. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was below 4 at all time-points.

Conclusions Pooled rates of most outcomes were better than what had been reported in the literature and within expected rates of those reported for the general population. Pre-conception counselling, planned pregnancies and a tight management in expert centres applying a tailored treatment approach may have contributed to the favourable pregnancy outcomes.