Fetal heart rate and blood flow velocity variability in the presence of increased nuchal translucency: a preliminary study

Abstract

K E Y W O R D S:blood flow velocity variability; heart rate variability; nuchal translucency ABSTRACTObjective To study the power spectrum distribution of heart rate and umbilical artery flow velocity variability in fetuses with increased nuchal translucency thickness (NT). 11-14 (median, 12) weeks. The NT group included 11 abnormal karyotypes: trisomy 18 (n = 3), 45,X (n = 4), trisomy 21 (n = 3) and a balanced translocation. Absolute heart rate as well as the coefficient of variation for both beat-to-beat heart rate variability and umbilical artery blood flow velocity variability were determined. The ratios of the integrated low-frequency components (0.05-0.2 Hz) and the integrated highfrequency ones (0.25-1.6 Hz; LH ratio) from normalized power spectrum distributions were established to reflect sympathovagal balance. Methods Doppler velocity waveforms were collected from long-lasting (> 20 s) umbilical artery recordings in 18 fetuses with increased NT (> 3 mm) and 18 normal controls matched for gestational age at ResultsThe mean heart rate was not significantly different between the two groups. However, mean heart rate variability and time-averaged flow velocity variability were significantly increased in the NT group, while there was no significant difference in the LH ratios between the two groups. The mean umbilical artery pulsatility index was significantly higher in the NT group. ConclusionThe autonomic nervous system does not seem to play a role in the altered cardiovascular homeostasis in the presence of increased fetal NT.

Fetal cardiac function between 11 and 35 weeks' gestation and nuchal translucency thickness

“…Increased afterload (distal to the aortic isthmus) when the NT is increased, could explain the decreased PV-AT found and the reported increased incidence of tricuspid regurgitation 41 . It is unclear if downstream placental resistance is altered in fetuses with increased NT, as reports are contradictory 37,42 . In early gestation, major changes in placental development occur along with the establishment of the intervillous circulation 43 .…”