A marginal placenta previa describes a placenta that lies within 2cm of the cervical os but does not overlie the os. Treatment depends on whether or not the woman has bleeding, how far along she is in her pregnancy and whether the previa persists on repeat ultrasounds. Marginal placenta previa may be treated conservatively with observation or more aggressively with Caesarean section delivery.
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Placenta previa may be seen on ultrasounds done in the second trimester. Many of them resolve as the pregnancy progresses. Therefore, a woman diagnosed with placenta previa early in her pregnancy should have a repeat ultrasound in the third trimester.
A woman diagnosed with a marginal placenta previa may be watched carefully as an outpatient if she has no history of vaginal bleeding, has no other symptoms such as uterine contractions and if she can get to a hospital quickly if she develops bleeding, pain or contractions. After 28 weeks of gestation, she should engage in pelvic rest that involves avoiding tampons and sexual intercourse.
Admission to the Hospital
A woman with vaginal bleeding from the placenta previa is admitted to the hospital for maternal and fetal monitoring. She may receive corticosteroids, which help fetal lungs mature. During her hospital course, she will be monitored for excessive blood loss, and her baby will be assessed for lung maturity. If she is unstable due to ongoing bleeding or if the fetus develops mature lungs as measured by amniocentesis, she may proceed to delivery.
Vaginal delivery is possible in certain women with marginal placenta previa, although most women who have a placenta within 2cm of the cervical os will require Caesarean section for delivery.
Women with a marginal placenta previa are likely to be delivered by Caesarean section. A woman who is actively bleeding, has a placenta covering the cervical os has a fetus whose head is not down will be delivered by Caesarean section.