WS15‐08Physiologic change of spiral arteries – what ultrasound can add?

Abstract

Physiologic change of spiral arteries is important adaptation of maternal vascular network for ongoing pregnancy. It is characterised by destruction of muscular layer of these vessels changing them to a low resistance vascular channels. Physiologic change was found to be incomplete in pregnancies complicated by pregnancy induced hypertension (PIH) and intrauterine growth retardation (IUGR). These changes were detected in vitro in histrologic studies but recently were investigated in vivo using Doppler ultrasound. In normal pregnancy the impedance to blood flow in spiral arteries measured by resistance (RI) and pulsatility (PI) indices significantly decrease toward the mid trimester (P < 0.05) and then remains stable. Similar observation was found in pregnancies complicated by PIH and IUGR. Both of these represent the second wave of trophoblastic invasion of spiral arteries. In pregnancies complicated by PIH and IUGR measured impedance indices were significantly higher compared to the matched normotensive women with normal fetal growth (P < 0.05), representing ht failure of the complete physiologic change of the spiral arteries. This is in concordance with histologic studies. Comparing the significance levels of blood flow in proximal and distal parts of uteroplacental circulation between investigated groups, the higher significance levels were obtained in terminal parts. This can have serious implication in designing further research protocols of the screening programmes for the PIH and IUGR based on the blood flow in uteroplacental circulation.