PRENATAL-DIAGNOSIS AND OUTCOME OF SUBAMNIOTIC HEMATOMAS

Subamniotic hematomas are classical placental pathological lesions res ulting from the rupture of chorionic vessels near the cord insertion. Most subamniotic hematomas are found after birth and result from exces sive traction on the umbilical cord at delivery. The developement of t hese lesions has been rarely reported in utero. We report here five ca ses of subamniotic hematomas diagnosed by ultrasound between 18 and 30 weeks of gestation. The sonographic features were those of a poorly r eflective oval-shaped cystic mass overlying the fetal plate of the pla centa and covered in a thin membrane. In all the cases, a cystic struc ture containing a thrombotic mass arising from the amniotic membrane, which was attached to the fetal placental surface, was found after del ivery. A high maternal serum alpha-fetoprotein level was found retrosp ectively in the four cases for which this information was available. T wo pregnancies were complicated by slow fetal growth, one by vaginal b leeding and one by polyhydramnios. These findings demonstrated that su bamniotic hematoma can be accurately diagnosed in utero by ultrasound and differentiated from other lesions of the placental chorionic plate . The findings also show that, although the lesion is located between the chorion and the amnion, it can be associated with fetomaternal hem orrhage and with fetal growth restriction.