Umbilical artery flow velocity waveform analysis in normal ovine pregnancy and after carunculectomy.

Twenty fetal lambs were studied in utero using continuous wave Doppler ultrasound to analyse the fetal umbilical artery flow velocity waveforms. Satisfactory waveforms were obtained. Prepregnancy surgical removal of uterine caruncles was used to produce intrauterine fetal growth retardation in 14 of these ovine pregnancies of whom 8 delivered a small for gestational age fetus. In only one fetus was the umbilical artery flow velocity waveform abnormal with a high systolic diastolic ratio. We conclude that the growth restriction occurring in the ovine fetus following a reduction of placental implantation sites is not related to a restriction in the fetoplacental circulation and this is different from the most frequently observed human fetal growth retardation.