<Li> Subamniotic or preplacental hematomas are contained within amnion and chorion . Rare . </Li> <P> Most patients with a small subchorionic hematoma are asymptomatic . Symptoms include vaginal bleeding, abdominal pain, premature labor and threatened abortion . </P> <P> Ultrasonography is the preferred method of diagnosis . A chorionic hematoma appears on ultrasound as a hypoechoic crescent adjacent to the gestational sac . The hematoma is considered small if it is under 20% of the size of the sac and large if it is over 50% . </P> <P> The presence of subchorionic bleeding around the gestational sac does not have a significant association with miscarriage overall . However, the case of intrauterine hematoma observed before 9 weeks of gestational age has been associated with an increased risk of miscarriage . In one study women who complied with instructions for bed rest for the duration of bleeding had a lower rate of miscarriage and a higher rate of term pregnancy than non-compliant women . The study had several limitations; results were severely confounded by inherent differences between compliant and non-compliant women . </P>

Bleeding between the uterine wall and placental membrane