Maternal smoking during pregnancy improves the anatomy of the hip joint in the female neonate

Abstract

Objective: Because the greater frequency of developmental dysplasia of the hip in the female could have an endocrine etiology, and because maternal smoking in pregnancy causes fetal endocrinedisequilibrium, we investigated the anatomy of the hip in neonates of smoking and non-smoking mothers.Methods: Clinical and sonographic examination was performed on 2066 hips of 521 male and512 female neonates. In 48 male and 53 female neonates, the mothers smoked during pregnancy.Results: The mean ± SD α angle in the male neonates of the non-smoking mothers was 62.3°± 5.1° and of the smoking mothers 62.1° ± 4.9° (p = 0.7). In the female neonates of the non-smoking and the smoking mothers, it was 60.7° ± 5.3° and 61.9°± 4.8°, respectively (p = 0.02). The difference between the male and the female neonates of the non-smoking mothers was significant (p < 0.000001), but there was no significantdifference between the female neonates of the smoking mothers and the male neonates (p = 0.5). Among the female neonates whose mothers were non-smokers, the number of those with hip type IIa or worsewas significantly greater than among the female neonates whose mothers were smokers. The clinical findings were in agreement with the sonographic findings.Conclusions: Maternal smoking duringpregnancy reduces the frequency of sonographic and possibly clinically detected hip dysplasia in female but not in male neonates. Nonetheless, because smoking causes numerous adverse effects on the fetusand child, it is contraindicated during pregnancy.