Low birth-weight in NSW, 1987: a population-based study.

The New South Wales perinatal data collection was used to examine the association between low birth-weight and some of its potential risk factors. The study population comprised all recorded singleton births to residents of NSW in 1987. Low birth-weight infants were categorized as either small for gestational age (SGA) or preterm (less than 37 weeks). Risk factors were analyzed separately for these categories. The risk factors examined were primarily demographic or reproductive history variables. Univariate analysis and multivariate logistic regression were used to evaluate the risk factors. The factors associated with SGA birth were mainly demographic (maternal age, parity, marital status, socioeconomic status, and ethnic group) while those associated with preterm birth had more reproductive history variables (maternal age, parity, marital status, prior spontaneous abortion, prior induced abortion, prior stillbirth or neonatal death, sex of infant). A first antenatal visit after 12 weeks had a statistically significant but small effect on both SGA and preterm birth.