The relationship between neonatal developmental dysplasia of the hip and maternal hyperthyroidism.

OBJECTIVE Development of the hip joint is complete by 11 weeks of gestation. As triiodothyronine and thyroxine are important regulators of early bone and muscle development, we hypothesized that excessive thyroid hormone in the early fetal period was a congenital risk factor of developmental dysplasia of the hip (DDH). Consequently, it was proposed that elevations of maternal thyroxine in the first trimester could alter the incidence of neonatal DDH. METHODS The patient population comprised a retrospective cohort of all children born in Yukiguni-Yamato General Hospital from 1996 to 2003 (n = 2137). All infants were physically assessed for DDH. Pregnancies were divided into normal, Graves disease (n = 15), and severe hyperemesis gravidarum in the first trimester (n = 39, which is associated with gestational transient hyperthyroidism in up to 73%). RESULTS From a total 2137 pregnancies, 21 children (18 female) were diagnosed with DDH. Thirteen affected infants were from normal pregnancies (0.63%), 3 from mothers affected with Graves disease (20%, P < 0.0001), and 5 from mothers with hyperemesis gravidarum (12.8%, P < 0.0001). CONCLUSIONS Developmental dysplasia of the hip is associated with first-trimester maternal hyperthyroidism, and infants of these mothers should be closely checked for hip abnormalities.