The patient should initially be observed closely with continuous fetal monitoring to assess for fetal distress. A complete blood count with platelets and a prothrombin time (INR) should be obtained and repeated serially if the bleeding continues. If hemorrhage is significant or if there is evidence of acute hypovolemia, the need for transfusion should be anticipated and an appropriate volume of red cells prepared with cross-matching. Ultrasound examination should be performed to determine placental location (eFigure 19–10 and 19–11). Digital pelvic examinations are done only after ultrasound examination has ruled out placenta previa. Administration of anti-D immune globulin may be required for women who are Rh negative.
Total placenta previa. Sagittal midline sonogram in the last trimester shows the placenta (P) completely covering the internal cervical os (arrowhead). F, fetus. (Reproduced, with permission, from Krebs CA, Giyanani VL, Eisenberg RL. Ultrasound Atlas of Disease Processes. Originally published by Appleton & Lange. Copyright © 1993 by The McGraw-Hill Companies, Inc.)
Placenta previa. Sagittal sonogram of the lower uterine segment in a patient with vaginal bleeding. The placenta (P) is seen to encroach upon the cervix (arrows) consistent with a marginal placenta previa. (Used, with permission, from Peter W. Callen, MD.)
Placenta previa occurs when the placenta implants over the internal cervical os. Risk factors for this condition include previous cesarean delivery, increasing maternal age, multiparity, and smoking. If the diagnosis is initially made in the first or second trimester, the ultrasound should be repeated in the third trimester. Persistence of placenta previa at this point is an indication for cesarean as the route of delivery. Painless vaginal bleeding is the characteristic symptom in placenta previa and can range from light spotting to profuse hemorrhage. Hospitalization for extended evaluation is the appropriate initial management approach. For pregnancies that have reached 37 weeks’ gestation or beyond with continued bleeding, cesarean delivery is generally indicated. Pregnancies at 36 weeks or earlier are candidates for expectant management provided the bleeding is not prodigious, and a subset of these women can be discharged if the bleeding and contractions completely subside.
C. Morbidly Adherent Placenta
Morbidly adherent placenta is a general term describing an abnormally adherent placenta that has invaded into the uterus. The condition can be further classified depending on whether the depth of invasion is limited to the endometrium (accreta), extends into the myometrium (increta), or invades beyond the uterine serosa (percreta). The most important risk factor for a morbidly adherent placenta is a prior uterine scar—typically from one or more prior cesarean deliveries. The focus of invasion usually involves the scar itself, and placenta previa is commonly associated with morbid adherence. Of serious concern for the field of obstetrics, the incidence of these syndromes has increased dramatically over the last 50 years commensurate with the increasing cesarean delivery rate.
After delivery of the infant, almost always in a repeat cesarean section, the morbidly adherent placenta does not separate normally, and the bleeding that results can be torrential. Emergency hysterectomy is usually required to stop the hemorrhage, and transfusion requirements are often massive. Because of the considerable increase in both maternal morbidity and mortality associated with this condition, careful preoperative planning is imperative when the diagnosis is suspected antenatally. Ultrasound findings such as intraplacental lacunae, bridging vessels into the bladder, and loss of the retroplacental clear space suggest placental invasion in women who have placenta previa. Importantly, however, even if ultrasound findings are subtle, an abnormally adherent placenta should be suspected in any patient with one or more prior cesarean deliveries and an anterior placenta previa. Ideally, delivery planning should involve a multidisciplinary team, and the surgery should take place at an institution with appropriate personnel and a blood bank equipped to handle patients requiring massive transfusion. It has been demonstrated that a systematic approach to management with a multidisciplinary team improves patient outcomes. Evidence-based recommendations regarding delivery timing are lacking, but the goal is to have a planned, late-preterm cesarean delivery. As such, delivery at 34–36 weeks in a stable patient seems a reasonable approach.
Placental abruption is the premature separation of the placenta from its implantation site before delivery. Hypertension is a known risk factor for abruption. Other risk factors include multiparity, cocaine use, smoking, previous abruption, and thrombophilias. Classic symptoms are vaginal bleeding, uterine tenderness, and frequent contractions, but the clinical presentation is highly variable. There is often concealed hemorrhage when the placenta abrupts, which causes increased pressure in the intervillous space. Excess amounts of thromboplastin escape into the maternal circulation and defibrination occurs. Profound coagulopathy and acute hypovolemia from blood loss can occur and are more likely with an abruption severe enough to kill the fetus. Ultrasound may be helpful to exclude placenta previa, but failure to identify a retroplacental clot does not exclude abruption. In most cases, abruption is an indication for immediate cesarean delivery because of the high risk of fetal death.
American College of Obstetricians and Gynecologists. Obstetric Care Consensus No. 7: Placenta accreta spectrum. Obstet Gynecol. 2018 Dec;132(6):e259–75.
American College of Obstetricians and Gynecologists. Practice Bulletin No. 183: Postpartum hemorrhage. Obstet Gynecol. 2017 Oct;130(4):e168–86. [Reaffirmed 2019]
et al. Association of implementing a multidisciplinary team approach in the management of morbidly adherent placenta with maternal morbidity and mortality. Obstet Gynecol. 2018 Nov;132(5):1167–76.
et al. Outcomes of planned compared with urgent deliveries using a multidisciplinary team approach for morbidly adherent placenta. Obstet Gynecol. 2018 Feb;131(2):234–41.