Objective: To determine whether the congenital cystic adenomatoid malformation (CCAM) volume ratio (CVR) is associated with fetal and postnatal outcome after prenatal diagnosis and antenatal expectant management in a provincial tertiary referral center that does not offer fetal surgery. Methods: Retrospective cohort of 71 consecutive cases of prenatally diagnosed CCAM meeting study criteria (1996–2004). CVR was calculated on the initial ultrasound at the referral center, and associated with hydrops (Fisher’s exact test) and a composite adverse postnatal outcome consisting of death, intubation for respiratory distress, extracorporeal membrane oxygenation, non-elective surgery for symptomatology, or respiratory infection requiring hospital admission (Mann-Whitney test). Results: A CVR >1.6 was significantly associated with hydrops (p = 0.003). In addition, the CVR was significantly associated with the composite adverse postnatal outcome (p = 0.004) at a mean age of follow-up of 41 months (range <1–117 months). For CVR and postnatal outcome, the area-under-the-curve receiver operating characteristic was 0.81 (95% CI 0.69–0.93, p = 0.006), and choosing a CVR cut-off of <0.56, the negative predictive value was 100% (95% CI 0.85–1.00). Conclusion: In a provincial referral center with antenatal expectant management of CCAM, the CVR was associated with hydrops and postnatal outcome, with a CVR <0.56 predictive of good prognosis after birth.