Human fetal cardiac function during the first trimester of pregnancy

Objective: To investigate first trimester human fetal cardiac function in relation to cardiac volume blood flow, and peripheral arterial and venous blood flow patterns. Methods: Transvaginal Doppler ultrasonography was performed in 16 uncomplicated pregnancies at 6+, 7+, 8+, 9+, and 10+ gestational weeks. The shape of the inflow waveform and the presence of atrioventricular valve regurgitation ( AVVR) were noted. The outflow mean velocity ( Vmean) was calculated. The proportions of the isovolumetric relaxation ( IRT%) and contraction times ( ICT%) of the cardiac cycle were defined. Ductus venosus and umbilical artery pulsatility indices ( PI) were obtained. Results: Every inflow waveform was monophasic before 9+ weeks. At 9+ weeks 11 of 16 and at 10+ weeks all waveforms were biphasic. At 7+ and 8+ weeks AVVR was documented in one case. At 9+ and 10+ weeks AVVR was present in four and seven fetuses, respectively. Mean ( SD) outflow Vmean increased between 6+ and 8+ weeks from 3.6 ( 1.5) to 8.4 ( 3.0) cm/ s ( p< 0.05). IRT% decreased significantly from 6+ to 7+ weeks ( 39.8 ( 2.6) to 19.2 ( 6.2), p< 0.001). ICT% decreased between 8+ and 9+ weeks from 13.2 ( 4.0) to 8.5 ( 2.5) ( p, 0.05). Ductus venosus PIs were unchanged. Umbilical artery Vmean increased between 7+ and 10+ weeks from 1.59 ( 0.51) to 5.06 ( 1.06) cm/ s ( p, 0.001) and PIs remained unchanged. Conclusions: The first trimester of pregnancy is characterised by significant improvements in cardiac diastolic and systolic function with a concomitant increase in cardiac volume blood flow. At 10+ weeks AVVR is a common finding. Placental volume blood flow increases significantly with no change in the placental vascular impedance.