IntroductionAn increased risk of preterm birth in women with joint hypermobility syndrome or Ehlers-Danlos syndrome is suspected. Material and methodsIn this nationwide cohort study from 1997 through 2011, women with either joint hypermobility syndrome or Ehlers-Danlos syndrome or both disorders were identified through the Swedish Patient Register, and linked to the Medical Birth Register. Thereby, 314 singleton births to women with joint hypermobility syndrome/Ehlers-Danlos syndrome before delivery were identified. These births were compared with 1247864 singleton births to women without a diagnosis of joint hypermobility syndrome/Ehlers-Danlos syndrome. We used logistic regression, adjusted for maternal age, smoking, parity, and year of birth, to calculate adjusted odds ratios for adverse pregnancy outcomes. ResultsMaternal joint hypermobility syndrome/Ehlers-Danlos syndrome was not associated with any of our outcomes: preterm birth (adjusted odds ratio=0.6, 95% confidence interval 0.3-1.2), preterm premature rupture of membranes (adjusted odds ratio=0.8; 95% confidence interval 0.3-2.2), cesarean section (adjusted odds ratio=0.9, 95% confidence interval 0.7-1.2), stillbirth (adjusted odds ratio=1.1, 95% confidence interval 0.2-7.9), low Apgar score (adjusted odds ratio=1.6, 95% confidence interval 0.7-3.6), small for gestational age (adjusted odds ratio=0.9, 95% confidence interval 0.4-1.8) or large for gestational age (adjusted odds ratio=1.2, 95% confidence interval 0.6-2.1). Examining only women with Ehlers-Danlos syndrome (n=62), we found a higher risk of induction of labor (adjusted odds ratio=2.6; 95% confidence interval 1.4-4.6) and amniotomy (adjusted odds ratio=3.8; 95% confidence interval 2.0-7.1). No excess risks for adverse pregnancy outcome were seen in joint hypermobility syndrome. ConclusionWomen with joint hypermobility syndrome/Ehlers-Danlos syndrome do not seem to be at increased risk of adverse pregnancy outcome.