A study of placental bed spiral arteries and trophoblast invasion in normal and severe pre‐eclamptic pregnancies

Endovascular trophoblast did not show an all or none invasive phenomenon in normal and pre-eclamptic pregnancies. More decidual than myometrial arteries were invaded in both groups of patients, and there was a gradient in the percentage of decidual and myometrial arteries invaded from normal pregnancy to pre-eclampsia. Morphological features in one spiral artery may not necessarily be representative of all of those in a placental bed.