RESULTS
Description of cases and controls
One or more amalgam fillings were placed during pregnancy in 3.5 percent of the women with a low-birthweight infant and in 5.3 percent of the women with an infant having a birth weight of greater than or equal to 2,500 g (table 1). There were no substantial differences with respect to the number of resin-based fillings, sealants, or crowns placed during pregnancy. Standard medical and socioeconomic risk factors for low birth weight were confirmed. When compared with mothers whose infant(s) weighed greater than or equal to 2,500 g, mothers with a low-birthweight infant were more likely to be less than 20 years of age, less likely to be Caucasian, less likely to have more than a high school degree, and more likely to have had inadequate prenatal care (table 1). Self-reported cigarette smoking during pregnancy, established or gestational diabetes, zero parity, and preecclampsia were identified as risk factors for low birth weight. Dental procedures other than restorative procedures were similar in both groups with the exceptions of orthodontic procedures, which were more prevalent among women with low-birth-weight infants, and preventive procedures, which were more prevalent among women with infants with a birth weight greater than or equal to 2,500 g (table 2).