Objective: To compare birth and early developmental screening outcomes for infants with and without in utero cannabis exposures. Study design: Observational cohort of women receiving prenatal care within a large health system, live birth between October 1, 2015 and December 1, 2017, and at least one infant visit. Cannabis exposure was through routine urine toxicology screen. Preterm birth, small for gestational age (SGA) birth, birth defects, and early developmental screening outcomes were assessed from birth and electronic health record data. Results: Of 3435 women, 283 (8.2%) had a positive urine toxicology screen. In utero cannabis exposure was associated with SGA birth, adjusted rate ratio (aRR) 1.69 (95% confidence interval [CI]: 1.22–2.34). Abnormal 12-month developmental screens occurred in 9.1% of infants with in utero cannabis exposure vs. 3.6% of those with negative maternal screens, aRR 1.90 (95% CI: 0.92–3.91). Additional birth outcomes were not associated with in utero cannabis exposure. Conclusions: Exposure to cannabis during pregnancy may adversely impact fetal growth.