Fetal heart rate and umbilico-placental Doppler flow velocity waveforms in early pregnancies with a chromosomal abnormality and/or an increased nuchal translucency thickness.

Fetal heart rate, umbilical artery pulsatility index, end-diastolic flow, nuchal translucency thickness and placental thickness were recorded in 250 women with a viable singleton pregnancy undergoing chorionic villous sampling for fetal karyotyping at 11-14 weeks of gestation. The fetal karyotype was normal in 210 cases and abnormal in 40, including 21 with trisomy 21, 13 with trisomy 18, three with triploidy, two with monosomy X and one with trisomy 13. A total of 52 fetuses with a normal karyotype had a nuchal translucency > or = 3 mm and were considered separately. There was a stable and significant increase in the mean fetal heart rate in trisomy 21 pregnancies compared to controls. No significant difference was found for the other variables between the groups. In chromosomally normal fetuses with an increased nuchal thickness, the development of fetal heart rate and compliance of the umbilico-placental circulation were within the normal ranges. Some fetuses with trisomy 18 or triploidy had an increased resistance to blood flow in the umbilical artery, which was probably due to abnormal placental development.