Five to 10 percent of women have vaginal bleeding in late pregnancy. The clinician must distinguish between placental causes (placenta previa, placental abruption, vasa previa) and nonplacental causes (labor, infection, disorders of the lower genital tract, systemic disease. The approach to bleeding in late pregnancy depends on the underlying cause, the gestational age at presentation, the degree of blood loss, and the overall status of the mother and her fetus. The cause of antepartum bleeding after mid-pregnancy is unknown in one-third of cases.
The patient should initially be observed closely with continuous fetal monitoring to assess for fetal distress. A CBC with platelets and an 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 21–6) (eFigure 21–7). 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.
Placenta previa. A. In this transvaginal image at 34 weeks' gestation, the anterior placenta completely covers the internal cervical os outlined by arrows. B. This transvaginal image at 34 weeks' gestation depicts a posterior placenta (arrow) that just reaches the level of the internal cervical os. (Reproduced, with permission, from Obstetrical Hemorrhage. In: Cunningham F, Leveno KJ, Bloom SL, Dashe JS, Hoffman BL, Casey BM, Spong CY (editors). Williams Obstetrics, 25th ed. McGraw Hill; 2018.)
Placental abruption. Shown to left is a total placental abruption with concealed hemorrhage. To the right is a partial abruption with blood and clots dissecting between membranes and decidua to the internal cervical os and then externally into the vagina. (Reproduced, with permission, from Obstetrical Hemorrhage. In: Cunningham F, Leveno KJ, Bloom SL, Dashe JS, Hoffman BL, Casey BM, Spong CY (editors). Williams Obstetrics, 25th ed. McGraw Hill; 2018.)
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 cigarette 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’ ...