Fig. 1From: Population-based study of the incidence of congenital hip dysplasia in preterm infants from the Survey of Neonates in Pomerania (SNiP)Effect of gestational age and birth weight on Graf classification in preterm infants of the SNiP cohort. For the left (p < 0.001) and right hip (p < 0.001), extremely preterm and very preterm neonates had a significantly higher incidence of mature hips than late preterm babies. χ 2 95% confidence interval 0.99–1.37Back to article page