Gray scale and color Doppler sonography in the third stage of labor for early detection of failed placental separation

Objective: The purpose of this study was the characterization of normal and abnormal third stage placental separation using gray scale and color Doppler sonography. Methods: The third stage of labor was examined in 62 patients using gray scale and color Doppler sonography. After identification of placental basal plate vessels by color Doppler sonography, the placentation site was examined throughout the third stage with combined gray scale and color Doppler mode. Placental separation from the myometrium was defined clinically and correlated to cessation of color Doppler detected blood flow in basal plate vessels. Results: Three sonographic phases of placental separation were: (1) latent = interval between delivery of the fetus and beginning placental separation; (2) detachment = mono- or multiphasic shearing off of the placenta and (3) expulsion = interval between completed separation and vaginal delivery of the placenta. In 57 cases with clinically normal placental separation blood flow between placenta and myometrium ceased immediately after delivery of the fetus during the latent period. In five cases manual or instrumental removal was necessary because of placenta adhaerens in one case and placenta accreta in four cases. The latter showed maternal blood flow from the myometrium deep into the placenta beyond the latent phase. Conclusion: Cessation of blood flow between the basal placenta and myometrium following delivery of the baby is the sonographic hallmark of normal placental separation. Persistent blood flow demonstrated by color Doppler sonography is suggestive of placenta accreta.