Antepartum hemorrhage is defined as bleeding from or in the genital tract prior tobefore delivery. Miscarriage, ectopic pregnancy, placenta previa, placental abruption, uterine rupture, and vasa previa are the most common causes of significant antepartum hemorrhage. Three to five percent of all pregnancies are complicated by antepartum hemorrhage, and it remains a leading cause of maternal and perinatal morbidity and mortality worldwide. Recognition of hemorrhage is often challenging, as the signs and symptoms of pregnancy may mimic normal physiologic changes of pregnancy. Yet, timely recognition and management of the hemorrhage are important for improving maternal and neonatal outcomes. Multidisciplinary institutional protocols should be established to standardize the approach and management of hemorrhaging parturients.
Keywordshemorrhage, hemorrhage protocol, miscarriage, placenta previa, placental abruption, placenta accreta, vasa previa
A 30-year-old woman, gravida 3, para 2, presents at 28 weeks’ gestation with vaginal bleeding. She has had a previous myomectomy and two previous cesarean deliveries. This is her first episode of bleeding in pregnancy. The estimated blood loss is about 200 mL. She is hemodynamically stable and her hematocrit is 30%. Ultrasonography reveals evidence of placenta accreta.
Antepartum hemorrhage is defined as bleeding from or in the genital tract before delivery. From 3% to 5% of all pregnancies are complicated by antepartum hemorrhage, and it remains a leading cause of maternal and perinatal morbidity and mortality worldwide.
Many reviews suggest that hemorrhage-related deaths may be avoided by improvements in care. Recommendations to improve care include (1) identification of women at high risk for hemorrhage, (2) improved recognition of the hemorrhage, and (3) timely management of the bleeding. Recognition of hemorrhage is challenging, as the physiology of pregnancy allows a pregnant women to lose more blood than a nonpregnant woman before showing signs or symptoms of hypovolemia. Furthermore, clinicians are poor at estimating blood loss. Multidisciplinary protocols have been developed to standardize the approach and management of hemorrhaging parturients.
Miscarriage, ectopic pregnancy, placenta previa, placental abruption, uterine rupture, and vasa previa are the most common causes of significant antepartum hemorrhage. The etiology of antepartum hemorrhage may vary with gestational age. Bleeding during early pregnancy (before 20 weeks’ gestation) can result from abnormal embryo implantation (e.g., placenta previa, placenta accreta, placental abruption, or vasa previa), miscarriage, ectopic pregnancy, gestational trophoblastic disease, dysfunctional uterine bleeding, and benign and malignant tumors of the reproductive tract. Among pregnancies complicated by bleeding in the first trimester, less than 50% progress normally beyond 20 weeks’ gestation; 10% to 15% are ectopic pregnancies, 0.2% are hydatidiform moles, and more than 30% result in miscarriage. The most common causes of bleeding beyond 20 weeks’ gestation are placental abruption and placenta previa.
Placental abruption —also referred to as abruptio placentae or placental separation—is defined as the premature separation of a normally situated placenta from its attachment to the placental decidua basalis before the birth of the fetus. Such separation is thought to result from a rupture of placental arteries or veins. Placental abruption occurs in 0.5% to 1.8% of all pregnancies, with approximately 40% of cases occurring after the 37th week of gestation, 40% occurring between the 34th and 37th weeks, and less than 20% occurring before the 32nd week. In 20% to 35% of cases, the bleeding may be concealed (i.e., no vaginal bleeding occurs); therefore attention to signs and symptoms of hypovolemia is important for appropriate management.
Placenta previa is implantation of the placenta in the lower uterine segment. It is classified by the degree to which the cervical os is encroached on or covered ( Fig. 33.1 ). As the lower uterine segment elongates during gestation, the amount of placental encroachment on the cervical os (and therefore the risk of bleeding) may lessen. Placenta previa occurs in up to 1% of third-trimester pregnancies.
On occasion, the placenta can adhere to the implantation site with an absent decidua, an abnormality that produces an absence of the physiologic line of cleavage through the decidual layer. The placenta can also invade the myometrium (placenta increta) or can extend through the myometrium and adhere to surrounding structures (placenta percreta).
Although the umbilical cord typically is attached to the placenta, in about 1% and 9% of single and twin gestations, respectively, it attaches to the chorioamniotic membranes. Such atypical or velamentous insertion exposes the umbilical vessels to trauma or compression as they traverse between the amnion and chorion to reach the placenta. Vasa previa exists when the velamentous umbilical vessels present ahead of the fetus, placing the fetus at even greater risk with rupture of membranes. Fetal exsanguination and demise often result.
Uterine rupture is defined as a defect in the uterine wall associated with fetal distress or maternal hemorrhage sufficient to require cesarean delivery or postpartum laparotomy. Rupture of the gravid uterus occurs in less than 1% of pregnancies, most often in patients with prior uterine trauma. Uterine scar dehiscence does not require surgical intervention. Although it is more common than true uterine rupture, most cases are asymptomatic and are not likely to cause maternal or fetal mortality. However, uterine scar dehiscence can result in significant morbidity, especially if it causes extension of the placenta laterally into major uterine vessels or there is abnormal placentation (placenta accreta, increta, or percreta). Cesarean scar rupture is more likely to occur if labor has been induced.
Miscarriage (i.e., spontaneous abortion) is defined as the loss of a recognized pregnancy before 20 weeks’ gestation. Miscarriages may be classified as threatened, inevitable, complete, incomplete, septic, recurrent, or missed. Between 15% and 20% of all clinically diagnosed pregnancies result in miscarriage, but the actual incidence may be higher depending on the definition of miscarriage used. Typically, the presentation includes a history of vaginal spotting or mild bleeding. When vaginal bleeding during the first 12 weeks of pregnancy is as heavy as normal menstrual blood loss, the pregnancy is rarely successful. Larger amounts of blood loss are observed with intrauterine fetal demise, especially at greater gestational ages.
Approximately 2% of pregnancies do not implant normally in the uterus, and the incidence appears to be increasing. Although ectopic pregnancies classically present as pelvic pain with intraperitoneal bleeding, they can also masquerade as a number of other entities, including appendicitis, ovarian cyst torsion, endometriosis, and pelvic inflammatory disease. Major blood loss with sudden death has been described. The risk of bleeding and the outcome correlate with the implantation site (e.g., isthmic or interstitial portion of the fallopian tube, ovary, cervix, abdomen) and the timing of diagnosis. Ectopic pregnancies may resolve spontaneously, be treated medically, or require laparoscopic or open surgery. Surgery is indicated in the presence of peritoneal signs, hemodynamic instability, or failed conservative management.
Unclassified bleeding accounts for almost half of antepartum bleeding (vasa previa is sometimes included in this category). It usually occurs in late pregnancy, and its cause either is unknown or does not become apparent until later. This type of bleeding, though typically mild with spontaneous resolution, is associated with high perinatal mortality rate (3.5%–15.7%). This may be due to placental dysfunction and higher rates of preterm labor in patients with unclassified bleeding.
Hemorrhage during pregnancy can be masked by the normal physiologic changes of pregnancy. As early as 6 to 8 weeks’ gestation, there is a progressive increase in plasma volume, reaching near-maximal volume (4700–5200 mL) by 32 weeks. This volume, which represents a 45% increase over that in nonpregnant women, is further augmented with multiple gestations and appears to be correlated with fetal weight. Placental chorionic somatomammotropin, progesterone, erythropoietin, and prolactin act in concert to increase red cell mass by 250 to 450 mL at term, an increase of 20% to 30% over pregestational values. The disproportionate increase in plasma volume versus red cell mass accounts for relative hemodilution and the maximal decreases in hematocrit seen by the middle of the third trimester. The resulting decrease in blood viscosity is believed to improve intervillous perfusion, reducing the risk for thromboembolic events. It also serves to reduce red cell loss during delivery. The changes in hematocrit and blood volume help increase maternal cardiac output. The heart rate increases from the fifth week of gestation to a maximal increment of 15 to 20 beats per minute by 32 weeks. This is in response to the relative anemia, reduced vagal control, and increased sympathetic tone. Increased stroke volume, which is primarily responsible for the early increase in cardiac output, is related to increased myocardial muscle mass in the first trimester and end-diastolic volume in the second and early third trimesters. Overall, there is a 30% to 50% increase in cardiac output during pregnancy. Half the increase occurs during the first 8 weeks of gestation. The greatest increase is seen immediately postpartum. The resultant anemia, tachycardia, and decreased blood pressure seen in normal pregnancy mimic similar physiologic derangements seen in hemorrhage.
These physiologic alterations of pregnancy allow the pregnant patient to tolerate 1000 to 1500 mL of blood loss without major hemodynamic changes. However, because nearly 20% of cardiac output (600–700 mL of blood) flows through the placental intervillous spaces each minute, obstetric hemorrhage can rapidly result in severe signs of shock ( Table 33.1 ). Also, owing to the potential for severe blood loss with antepartum bleeding, the characteristics of the common causes of such bleeding should be reviewed to assist in early diagnosis and treatment ( Table 33.2 ).