Doppler ultrasonography of endovascular trophoblast plugs/ aggregates

Published experiments strongly challenge the classic theory of endovascular trophoblast (EndTb) plugs and the absence of placental perfusion in the early first trimester. These studies suggest that within the spiral arteries (SAs) lumens, the "plugs" are incomplete, resulting in local stenosis-a structure previously difficult to visualize in vivo.

Pregnant women (n = 3474) were recruited and stratified into ten groups based on gestational age (range: 5 to 32⁺⁶ weeks). Detection rates of DT visualized via color Doppler flow imaging (CDFI) and pulsed-wave Doppler (PW) were observed and recorded, while hemodynamic parameters were collected and statistically analyzed across pregnancy stages. Additionally, DT blood flow parameters were measured and analyzed in a cohort of 145 women during uterine contractions.

In 3474 pregnant women, blood flow parameter variation was greater in the first trimester and decreased progressively, stabilizing in the second and third trimesters. In 145 healthy pregnant women, DT blood flow velocity increased during uterine contractions and returned to baseline afterward.

Doppler ultrasound can identify the location of the DT. In normal pregnancy, stenosis of the DT aperture structure results in localized hemodynamic acceleration, which can be dynamically modulated by uterine smooth muscle tone and amniotic cavity pressure via Braxton Hicks contractions. We provide new evidence suggesting that maternal blood enters the intervillous space (IVS) earlier than previously reported.