During the first half of pregnancy, extravillous trophoblast (TB) cells invade the decidua and myometrium (interstitial TB) and the uterine spiral arteries (endovascular TB). Invasion results in ''physiological transformation" of the spiral arteries characterized by a loss of normal musculo-elastic structure and replacement by amorphous fibrinoid material in which TB cells are embedded. In pre-eclampsia and FGR there is failure of TB invasion and consequent spiral artery transformation (Lyall and Robson, 2000).
Several studies have shown that uterine artery FVW indices are increased in women where there is failure of TB invasion on placental bed biopsy (Lin etal., 1995; Sagol et al., 1999). Between 73 and 90% of cases with a uterine artery systolic/diastolic (S/D) ratio S/D > 2.5 or an RI > 0.58 have absent TB migration into the myometrium (Lin et al., 1995; Sagol etal., 1999). Sagol etal. (1999) reported early diastolic notches in 57% of women with impaired
TB migration compared to 13% in those with normal migration. However, absence of physiological transformation of spiral arteries has also been reported in women with normal uterine artery Doppler FVW1 (Aardema et al., 2001).
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...