We conducted a retrospective review of prenatal sonograms of all fetuses (n = 25) with left sided congenital diaphragmatic hernia undergoing in utero surgical repair of the defect at the University of California, San Francisco, Fetal Treatment Center. Sixteen candidates were selected for analysis to determine reliable predictors of liver herniation. Bowing of the umbilical segment of the portal vein (portal sinus) to the left of midline and coursing of portal branches to the lateral segment of the left hepatic lobe toward or above the diaphragmatic ridge were the best predictors for liver herniation into the fetal thorax (positive predictive values of 85% and 100%, respectively). The stomach position was a good predictor if observed in a posterior or midthoracic location (positive predictive value = 100%). However, this occurred in only 7 of 16 (44%) cases. Visibility of the right lung was less informative (positive predictive value = 63%). We do not recommend in utero primary closure of congenital diaphragmatic hernia when there is sonographic evidence of liver herniation into the fetal thorax.