Controversy continues regarding the nutritional value to the fetus of swallowed amniotic fluid. To clarify this issue further, esophageal ligations were performed to prevent deglutition in utero in 63 fetal rabbits during the final trimester of pregnancy. Compared with sham-operated littermate controls, the fetuses that were ligated for periods of 4, 5, or 6 days showed significant reductions in weight of 6.1, 18.9, and 9.2%, respectively. These results compare well with the magnitude of weight reduction seen clinically in patients with esophageal atresia. Significant but less consistent reductions were also noted in crown-rump length and biparietal diameter. No significant differences were seen in either body composition or gastrointestinal tract histology. These results indicate that swallowed amniotic fluid does play a role in fetal nutrition and may be particularly important in the later stages of gestation when placental function is limited.