Purpose: Detection of congenital lower limb deformities often occurs at the time of routine prenatal ultrasound. Counseling referred patients on the basis of these abnormal ultrasound findings presents a challenge for orthopedic surgeons, given limited reports on the accuracy of ultrasound findings in these conditions. In this study, we aimed to determine the accuracy of prenatal ultrasound in the diagnosis of lower extremity congenital disorders. Additionally, we aimed to assess the ability of ultrasound measurement to accurately predict postnatal limb length discrepancy. Methods: Electronic medical records were queried to identify patients referred to our tertiary care medical center for prenatal ultrasound between 2004 and 2015 due to a suspicion of tibial hemimelia, fibular hemimelia, posteromedial tibial bow, or proximal femoral focal deficiency (PFFD). The medical records of both mother and infant were retrospectively reviewed to identity prenatal ultrasound diagnosis and measurements of the lower extremities, postnatal radiographic imaging and postnatal confirmation of diagnosis. Results: Thirteen cases were identified in which there was a suspicion of lower limb deformity based on prenatal ultrasound: tibial hemimelia (2 cases), fibular hemimelia (4 cases), posteromedial tibial bow (5 cases), distal athrogryposis (1 case), and PFFD (1 case). The mean gestational age at time of diagnosis is 19.2 weeks, ranging from 15 to 23 weeks. Prenatal ultrasound diagnosis was confirmed as accurate in 12 of 13 cases (92.3%). In the 6 patients in which limb length difference was calculated prenatally, the percent of growth inhibition was compared with postnatal radiographic measurements. There was a high degree of agreement between the measurements, with ICC=0.803 (95% CI = 0.21-0.97; p=0.009). Conclusion: Prenatal ultrasound can accurately detect congenital lower limb deformities. In cases involving suspected limb length discrepancy, ultrasound measurements of limb segment length can be useful in determining severity and can guide counseling of families regarding limb length difference at maturity. Prenatal identification of lower extremity congenital deformities can help physicians counsel parents regarding their child’s expected leg length difference, possible treatment plans, and functional outcomes.