Demographic and reproductive factors associated with hemifacial microsomia.

Objective: To identify demographic and reproductive risk factors for hemifacial microsomia in offspring.

Design: In a case-control study, maternal interviews were conducted within 3 years after delivery. Cases with hemifacial microsomia were ascertained from craniofacial centers in 26 cities in the United States and Canada. Controls were patients of the cases' pediatricians. Two hundred thirty-nine cases were compared with 854 controls. Odds ratios for various infant and maternal factors were estimated.

Results: Cases had lower birth weights, were more often male or a twin, and had more relatives with craniofacial malformations or hearing loss than controls. Case mothers had lower family incomes, had a lower body mass index, had more vaginal bleeding in the second trimester, and were more likely to have had a spontaneous abortion in a previous pregnancy.

Conclusions: Nonmodifiable factors (age and parity) were not associated with hemifacial microsomia risk. Factors that are related to poverty (low family income, late recognition of pregnancy, and low body mass index) are associated with an increase in risk. High risk estimates for multiple pregnancies and second-trimester vaginal bleeding suggest a vascular etiology.