Serum 17 beta-estradiol in newborn and neonatal hip instability.

This study evaluates the association between the level of 17 beta-estradiol in the umbilical cord blood and neonatal hip instability (NHI) in a population-based prospective case-control study comprising 2,185 consecutively newborns. beta-Estradiol levels were measured with a standard fluoroimmunoassay kit. Neonatal hip instability was determined by the anterior dynamic ultrasound method. An increased risk of NHI was found after breech malposition and in girls. Levels of beta-estradiol were higher in boys without NHI than in girls. A negative association between beta-estradiol level and parity was found. A significant association between beta-estradiol level and NHI was shown in boys with low serum concentrations. High levels of beta-estradiol tended to be associated with an increased risk of NHI in girls. An association was found between gender, parity, and beta-estradiol level in cord blood. No firm conclusion on the association between NHI and beta-estradiol level can be made; the possible association may be gender-dependent.