Hepatoblastoma is a rare embryonal tumor with unknown etiology. The authors conducted a case-cohort study using public health surveillance data sets to examine perinatal risk factors for hepatoblastoma. Hepatoblastoma cases (n=58) diagnosed between 1985 and 2001 were identified from the New York State Cancer Registry and were matched to electronic birth records for 1985–2001 from New York State, excluding New York City. Controls (n=6,056) were selected from the birth cohorts for the same years. Having a birth weight less than 1,000 g was associated with a strongly increased risk of hepatoblastoma (relative risk (RR)=56.9, 95% confidence interval (CI): 24.0, 130.7). After adjustment for birth weight, a moderately increased risk of hepatoblastoma was found for younger maternal age (<20 years vs. 20–29 years: RR=2.5, 95% CI: 1.0, 5.5), presumptive use of infertility treatment (RR=9.2, 95% CI: 2.1, 31.5), maternal smoking (RR=2.1, 95% CI: 1.0, 4.2), and higher maternal prepregnancy body mass index (body mass index of 25–29 vs. 20–24: RR=2.9, 95% CI: 1.2, 7.6).