Clinics in Mother and Child Health

Abstract

Risk Factors for Developmental Dysplasia of the Hip in the Newborn Data from the Swedish Medical Birth Register

Bengt Kallen

Background: Developmental dysplasia of the hip (DDH) is a common anomaly in the neonate which, if not treated, can result in chronic hip problems. In the previous literature some risk factors are known: female sex, first parity, breech presentation and family history.

Material and methods: The Swedish Medical Birth Register was used to identify infants with neonatal DDH for the period 1973-2011 and data from 1998-2011 were used in order to identify and quantify risk factors. Analysis was performed with Mantel-Haenszel methodology with estimates of odds ratios and approximate 95% confidence intervals were estimated with Miettinen’s method.

Results: Among all infants born (n=3,977,681), 34,530 had DDH. The rate of DDH diagnoses declined markedly during the 1980s but was relatively constant after 1998. A marked geographical variation was found. The previously identified risk factors were verified: female sex, breech presentation, family history, first parity. An increasing risk with maternal age (adjusted for parity) was seen and a reduced risk at maternal smoking. There is a strong linear regression between gestational duration or birth weight and presence of DDH while only reduced and not excess intrauterine growth markedly affected DDH rate. Caesarean section did not change the DDH risk at vertex presentation but reduced it at breech presentation. Maternal use of anticonvulsants increased the risk for DDH but a decreased risk was seen after maternal use of insulin or antidepressants.

Conclusions: The study has demonstrated previously little known risk factors for DDH.