Descriptive epidemiology of hemivertebrae, Hawaii, 1986-2002.

The intent of this study was to report on the epidemiology of hemivertebrae. Cases were derived from a population-based birth defects registry in Hawaii and comprised all infants and fetuses with hemivertebrae delivered during 1986-2002. Hemivertebrae rates per 10 000 births were determined for selected factors and comparisons made by calculating the rate ratio (RR) and 95% confidence interval (CI). Forty-two cases of hemivertebrae were identified, for a total rate of 1.33. Forty-one of the cases were live births, of which 26.83% expired within one year after delivery. Other major structural birth defects were found in 95.24% of the cases. The most frequent associated defect was scoliosis, affecting 54.76% of the cases. The rate among females was significantly lower than among males (RR 0.48, 95% CI 0.23-0.94). The rate was lower with maternal age > or =35 years (RR 0.50, 95% CI 0.10-1.57) and higher with birth weight < 2500 g (RR 5.96, 95% CI 2.84-11.90) and gestational age < 38 weeks (RR 3.94, 95% CI 2.01-7.64). The majority of hemivertebrae cases had other major structural birth defects. Hemivertebrae occurred predominantly among males and risk was lower with increased maternal age. Rates for hemivertebrae were higher with lower birth weight and gestational age. Further population-based research involving larger study populations are recommended to confirm these observations.