Comparison of colour Doppler features and pathological findings in complicated early pregnancy

Resistance index (RI) and pulsatility index (PI) in the uterine and spiral arteries, uterine artery peak systolic velocity and intervillous blood flow were recorded by transvaginal colour Doppler imaging in 30 missed abortions and 30 normal pregnancies matched for menstrual age. Pathological examination was performed in both groups within 24 h of Doppler investigation. The mean uterine PI was significantly (P < 0.01) higher in missed abortions compared to normal controls, whereas the mean uterine RI and peak systolic velocity and spiral RI and PI did not differ. A continuous intervillous flow was found in 16 out of 23 (69.6%) of the complicated pregnancies before 12 weeks of gestation whereas it was not found in controls. In the missed abortion cases, the trophoblastic shell was fragmented or absent in 53% and trophoblastic infiltration and physiological changes in the spiral arteries were reduced or absent in 43 and 63%, respectively. These findings were not related to normal or abnormal Doppler indices. Extended dislocation of the trophoblastic shell and a massive infiltration of the intervillous space and placental bed by maternal blood was also found in cases presenting with a continuous intervillous blood flow before 12 weeks of gestation. These findings suggest that abnormal flow velocity waveforms in early pregnancies complicated by embryonic death are related to deficient placentation and dislocation of the trophoblastic shell that follows embryonic demise. The premature entry of maternal blood into the intervillous space disrupts the materno-embryonic interface and is probably the final mechanism causing abortion.