Assessment of the Early Foetal Circulation
With the advent of transvaginal Doppler ultrasound, it became feasible to examine the maternal uterine and foetal circulation as early as the first trimester of pregnancy. Particularly during the late first and early second trimester, marked developmental changes occur both at foetal and placental level which should have an impact on foetal cardiovascular performance. Foetal heart rate changes from 170–180 bpm to 140–150 bpm with appearance of beat to beat variation most likely resulting from parasympathetic nerve development . At the same time there is a remarkable differentiation in foetal movement patterns. Furthermore, around 14 weeks a continuous intervillous flow pattern has been observed . This is associated with an abrupt increase of the mean uterine blood flow velocity, which possibly corresponds to the complete dislocation of the trophoblast plugs, allowing uninhibited blood supply to the intervillous space. An overview on human foetal cardiovascular Doppler research in early pregnancy will be presented.
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