Physiological conversion of the maternal spiral arteries is key to a successful human
pregnancy. It involves loss of smooth muscle and the elastic lamina from the vessel wall as
far as the inner third of the myometrium, and is associated with a 5–10-fold dilation at the
vessel mouth. Failure of conversion accompanies common complications of pregnancy,
such as early-onset preeclampsia and fetal growth restriction. Here, we model the effects of
terminal dilation on inflow of blood into the placental intervillous space at term, using …