Placenta Previa

Placenta Previa Leave the first rating Students also studied Terms in this set (13) Science MedicineObstetrics Save Occult Spinal Dysraphism (OSD)

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nguyenniferPreview Abruptio Placentae vs Placenta Pre...10 terms kiwe0410Preview Placental Abruption 17 terms nguyenniferPreview Neonat 20 terms ngu Definitionpresence of placental tissue that extends over the internal cervical os. Sequelae include the potential for severe bleeding and preterm birth, as well as the need for c/s Incidence3.5 - 4.6/1000 births Incidence is several-fold higher early in gestation, but most of these cases resolve before delivery Risk factors1. previous placenta previa

• previous c/s
• multiple gestation
• multiparity
• advanced maternal age
• infertility treatment
• previous abortion
• previous intrauterine surgical procedure
• maternal smoking
• maternal cocaine use
• male fetus
• non-white ethnicity

Pathophysiologyplacental bleeding is thought to occur when gradual changes in the cervix and lower uterine segment apply shearing forces to the inelastic placental attachment site, resulting in partial detachment.Vaginal examination or coitus can also disrupt the intervillous space and cause bleeding.Bleeding is primarily maternal but fetal bleeding can occur if a fetal vessel is disrupted.Clinical features: US1-6% of pregnant women display sonographic evidence of a placenta previa between 10-20 weeks gestation.Majority of these women are asymptomatic and 90% of these early cases resolve.Anterior placenta previa appears to resolve more often and quickly than a posterior placenta previa.Why does the majority of placenta previas at 20 week resolve at term?

Two schools of thought:

• Lower uterine segment lengthens from 0.5 cm at 20 weeks to >5 cm at term,

relocating the stationary lower edge of the placenta away from internal os.

• Trophotropism: progressive unidirectional growth of trophoblastic tissue toward

the fundus within the relatively stationary uterus results in upward migration of the placenta.Clinical presentation1. painless vaginal bleeding (70-80% of cases)

• uterine contractions (10-20% of cases)

Associated conditions1. placenta accreta

• preterm labour

3. PROM

• malpresentation

5. IUGR

• vasa previa
• velamentous umbilical cord
• congenital anomalies
• amniotic fluid embolism

Maternal morbidityplacenta previa increases risk of antepartum, intrapartum, and postpartum hemorrhage.For this reason, women with placenta previa are more likely to receive transfusions, undergo hysterectomy, uterine/iliac artery ligation, or embolization of pelvic vessels to control bleeding.Recurrence4-8% recurrence in subsequent pregnancies

Route of delivery: previac/s is always indicated when there is sonographic evidence of a complete placenta previa and a viable fetus.Vaginal delivery may be considered in rare circumstances, such as in the presence of a fetal demise or a pre-viable fetus, as long as the mother remains hemodynamically stable.When the placenta reaches the internal os but does not cross it, it has been hypothesized that vaginal delivery can occasionally be performed because the fetal head tamponades the adjacent placenta, thus preventing hemorrhage.However, these pregnancies remain at high risk for intrapartum hemorrhage.Route of delivery: low placentarates of c/s and antepartum bleeding decrease as the distance between the placental edge and internal os increase.General consensus of a reasonable possibility of vaginal delivery without hemorrhage when the placenta is >20 mm from internal os, so a trial of labour is appropriate if there are no other contraindications to vaginal birth.When distance is between 1-20 mm, rate of c/s ranges from 40-90%. Data from one study supports vaginal delivery attempt when placental edge is >10 mm from internal os.Timing of C/SSchedule C/S at 36-37 weeks.Incision of the placenta should be avoided as this increases the risk of fetal hemorrhage.Preoperative or intraoperative sonographic localization is helpful in determining the position of the hysterotomy incision.A vertical incision may need to be made in the lower uterine segment where the placenta is not located, however, this often results in extension into the upper uterine segment.When incision of the placenta is unavoidable, the infant should be delivered rapidly and the cord promptly clamped.