A 29-year-old woman, gravida 2 para 1, at 32 weeks gestation comes to the emergency department due to heavy vaginal bleeding. The bleeding started an hour ago. It was light initially and associated with only mild abdominal pain, but both the bleeding and the pain have increased, and now the pain is constant and severe. The patient has no chronic medical conditions. Her prior pregnancy was a term vaginal delivery complicated by preeclampsia with severe features. Blood pressure is 156/98 mm Hg, and pulse is 112/min. The uterus is firm and tender. Pelvic examination reveals heavy bleeding from the cervical os. Which of the following is the most likely cause of this patient's current presentation?
Abruptio placentae | |
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This patient in the third trimester with painful vaginal bleeding likely has abruptio placentae, the premature separation of the placenta from the myometrium prior to fetal delivery. Placental abruption occurs when maternal vessels rupture at the uteroplacental interface (ie, decidua basalis); the resultant bleeding causes placental separation from the uterine myometrium. Blood can also accumulate between the placenta and uterine wall and cause an acute increase in intrauterine pressure, resulting in severe abdominal pain, uterine irritability (ie, high-frequency contractions), and a tender, firm uterus.
In this patient, abruptio placentae is likely a complication of preeclampsia, a hypertensive disorder of pregnancy that causes widespread endothelial cell damage. Endothelial cell dysfunction results in dysregulated vascular tone (eg, hypertension) and increased vessel fragility. Preeclampsia also impairs early spiral artery development needed to supply blood to the fetus and placenta. As a result, patients with preeclampsia have abnormally high-resistance spiral arteries that produce low placental perfusion, ischemia, and possible placental infarction, all of which increase the risk of abruptio placentae.
(Choice A) The abnormal invasion of trophoblast into uterine myometrium (eg, placenta accreta) can cause heavy vaginal bleeding. However, this disorder is typically diagnosed after fetal delivery when the placenta does not detach from the uterine wall, resulting in postpartum (not antepartum) hemorrhage.
(Choice B) Placenta previa, the extension of placental tissue over the cervix, can cause antepartum bleeding. However, placental bleeding from this location can readily exit the uterus via the cervix, so patients typically do not have severe abdominal pain or a firm, tender uterus.
(Choice C) Physiologic cervical dilation (ie, spontaneous labor) can progress from light vaginal bleeding with mild abdominal pain to heavier bleeding during contractions. Labor pain, however, is typically intermittent, and the uterus relaxes between contractions.
(Choice E) Rupture of the uterine myometrium and serosa can cause abdominal pain and heavy vaginal bleeding. However, in the classic presentation, fetal parts are palpable through the maternal abdominal wall and patients do not have a firm uterus. In addition, this patient has no risk factors (eg, prior cesarean delivery), making this diagnosis less likely.
Educational objective:
Abruptio placentae is caused by rupture of maternal vessels at the uteroplacental interface that leads to premature separation of the placenta from the myometrium. Patients typically have painful vaginal bleeding and a tender, firm uterus. Preeclampsia increases the risk of abruptio placentae.