Objectives.Use of antepartum tests of fetal well-being is widespread even though effectiveness in preventing fetal damage or stillbirth has not been established. The study objective was to examine whether aggressive use of these tests might contribute to increased rates of other birth outcomes, including low birth weight (LBW).Methods.A total of 3,235 low-income women receiving care from 28 clinic sites were studied. All women were eligible for Medi-Cal benefits. Clinic sites were classified as aggressive, moderate, or low users of antepartum tests. The relations between patient risk factors, clinic testing style, LBW, and other pregnancy outcomes were examined using multiple logistic regression.Results.After adjustment for risk factors, patients seen by aggressive testers had a risk of LBW higher than patients receiving care from moderate testers (odds ratio = 1.65;P<0.01). Rates of LBW within patients receiving care from moderate and low testers did not differ (P= 0.22). Patients seen by aggressive testers also had higher rates of preterm delivery, cesarean delivery, and provided more expensive care.Conclusions.Although antepartum testing is intended to prevent fetal distress, extremely aggressive use of antepartum testing may have unfavorable effects on LBW and other pregnancy outcomes. More attention should be paid to variation in obstetric practices in evaluations of the costs and effectiveness of public prenatal care programs.