ABSTRACT
The terminal parts of the uteroplacental circulation include spiral arteries and intervillous space. In pregnancy, spiral arteries are invaded by trophoblast leading to their physiological change. This is a necessary adaptation of pre-existing vessels for ongoing pregnancy. Blood flow in the intervillous space is fully dependent on blood flow in the spiral arteries. In pregnancies complicated by pregnancy-induced hypertension and intrauterine growth restriction, the physiological change of the spiral arteries was found to be incomplete. In this review, we will present the complex circulation of the spiral arteries and intervillous space in normal pregnancy and pregnancies complicated by pregnancy-induced hypertension, assessed by ultrasound techniques.