OC244: Blood pressure estimation in the human fetal descending aorta

Abstract

The objective of this study was to estimate fetal blood pressure from 2D color Doppler- derived aortic blood flow and diameter waveforms by applying the Womersley model in combination with the two-element Windkessel model, assuming constant pulse-wave velocity during the second half of pregnancy. A total of 21 women with uncomplicated singleton pregnancies between 19 and 41 weeks of gestation consented to participate in the study. Ultrasound color Doppler cineloops of the fetal descending aorta were obtained with a Philips ATL HDI 5000 (Bothell, WA, USA) ultrasound system, using a C5-2 curved-array transducer. The product option ‘Research Link’ was applied to export the digital data to an external computer for offline analysis. A statistically significant eightfold increase was observed in aortic compliance. The compliance Ca exhibited a log linear relationship with the gestational age as Log(Ca (mmHg/mL)) = 0.098 · ga − 6.42 (R2 = 0.72). The aortic downstream peripheral resistance decreased fourfold during the same time. Rp exhibited an exponentially decaying relationship with gestational age as Log(Rp (mmHg.s/mL)) = − 0.0065 · ga + 3.38 (R2 = 0.45). The systolic aortic pressure regression line increased linearly from 37 mmHg at 20 weeks' gestation to 58 mmHg at 40 weeks of gestation. The mean aortic pressure regression line increased linearly from 28 mmHg at 20 weeks' gestation to 45 mmHg at 40 weeks of gestation. The mean ( ± SD) diastolic pressure was 21 (+ 9.5) mmHg and did not change significantly with the gestational age. This study demonstrates the feasibility of estimating arterial blood pressure in the human fetus. The fetal mean arterial pressures are comparable to the aortic pressures shortly after birth in neonates born at the same gestational age.