Trophoblastic Invasion and Vascular Remodeling in Pregnancy

Normal Pregnancy Characteristics

In normal pregnancy, spiral arteries undergo extensive remodeling through deep trophoblastic invasion, transforming them into significantly distended, low-resistance vessels, according to the American College of Obstetricians and Gynecologists 1, 2
The remodeled vessels extend into the inner third of the myometrium, creating optimal placental perfusion, as recommended by the American College of Obstetricians and Gynecologists 1, 2
This transformation results in a low-impedance, high-flow circulation reflected by high velocity and continuous forward flow in diastole on Doppler assessment, as stated by the American Heart Association 3, 1
The process optimizes intervillous placental blood flow and delivery of oxygen and nutrients to the fetus, according to the American College of Obstetricians and Gynecologists 3

PIH and preeclampsia are fundamentally characterized by failure of trophoblastic invasion of the myometrial spiral arteries, resulting in reduced uteroplacental perfusion and persistent high-resistance circulation, as described by the American College of Obstetricians and Gynecologists 1, 2, 4
The failed remodeling creates reduced placental perfusion and placental ischemia, according to the American College of Obstetricians and Gynecologists 1, 2, 4
This results in high-impedance circulation detectable on uterine artery Doppler as elevated pulsatility index >95th percentile or presence of diastolic notch, as stated by the American Heart Association 3, 1
The ischemic placenta releases anti-angiogenic factors (sFlt-1, sEng) causing systemic endothelial dysfunction and the maternal syndrome of preeclampsia, according to the American Heart Association 5, 6, 4
Attenuated reductions in systemic vascular resistance and impaired tolerance to plasma volume expansion characterize the hemodynamic profile, as described by the American Heart Association 5, 6
Deficient natriuretic peptide signaling contributes to inadequate vascular adaptation, according to the American Heart Association 5, 6