Uteroplacental circulation during the first trimester of normal and abnormal pregnancy.

The aim of this study was to evaluate the uteroplacental vascular characteristics during the first trimester of normal and failed pregnancies. A clinical descriptive study was conducted using colour Doppler ultrasound in 45 women with normal pregnancies (group A) and 44 with non-embryonic sac or missed abortions (group B). The mean gestational age in these two groups was 9.3 and 7.6 weeks respectively (P < 0.01). The number of myometrial blood vessels (arteries and veins identified by power Doppler mapping), the quantity of intervillous flow, the resistance index (RI) for the arterial system, and the pulsatility index (PI) of the myometrial arteries were evaluated. The number of myometrial blood vessels in group A was lower than that in group B. The intervillous flow was observed in some cases from early pregnancy and more often after 10 weeks. This characteristic was observed significantly more frequently in group B than in group A. The RI and PI in the uterine arteries were significantly higher in group A than in group B. The RI and the PI of the uterine arteries decreased with the advance of gestational age in both groups. Colour Doppler ultrasound provides information about uteroplacental circulation during the first trimester and indicates early development of intervillous circulation. Although a greater uteroplacental blood circulation was observed in failed pregnancies, the overlapping between groups severely limits the application of this characteristic in clinical practice.