Vaginal Bleeding

Nonpregnant Patients

The mean time between menstrual periods is 28 days (±7 days), with menstruation generally lasting for 5 days. It is considered abnormal to bleed for more than 7 days. The average blood loss per menstruation is 35 mL; a loss of more than 80 mL is abnormal.

Since 2011, the American College of Obstetricians and Gynecologists (ACOG) has recommended the PALM-COEIN classification system, which uses the all-inclusive term abnormal uterine bleeding (AUB) and divides the causes of AUB into structural and nonstructural causes. Structural causes include p olyps, a denomyosis, l eiomyomas, and m alignancy ( PALM ). Nonstructural causes include c oagulopathy, o vulatory dysfunction, e ndometrial, i atrogenic, and n ot yet classified causes ( COEIN ). The use of the term dysfunctional uterine bleeding is no longer recommended.

Approximately 50% of cases of excessive menstruation fall under the nonstructural PALM-COEIN category of ovulatory dysfunction, which includes anovulatory bleeding. If a woman does not ovulate, there is no corpus luteum to produce progesterone, which results in estrogen being unopposed. Unopposed estrogen causes the endometrium to proliferate to the point at which it becomes unstable and begins to break down, causing irregular and unpredictable bleeding to occur. Cyclical heavy bleeding can also occur in the setting of regular ovulation (ovulatory bleeding).

Leiomyomas (fibroids) are benign tumors of the uterus that can be associated with significant morbidity including excessive menstrual bleeding. Submucosal fibroids (fibroid that project into the uterine cavity) are especially prone to unpredictable and heavy uterine bleeding because they result in increased endometrial surface area that prevents uterine contractions from adequately compressing the vessels on the surface of the endometrium. Fibroids are common and occur almost exclusively among reproductive-age women. The incidence increases with age and is highest for women ages 45 to 49 years. Black women are disproportionally affected (rates twofold to threefold higher). Cervical polyps, which commonly occur in multiparous women in their 40s and 50s, are friable and prone to bleeding.

Pregnant Patients

Pregnant women may experience bleeding throughout their pregnancy. In early pregnancy, ectopic pregnancy causes hemorrhage into the fallopian tube by disrupting of the blood supply to the ectopic gestational sac. In addition, the size of the growing gestational sac can rupture through the tubal wall.

After the 20th week of pregnancy, vaginal bleeding can be caused by placenta previa, in which the placenta completely or partially covers the internal cervical os. As the lower part of the uterus becomes thinner during the third trimester in preparation for labor, bleeding can occur. Placental abruption causes bleeding when the placenta tears away from the uterine wall. This can occur spontaneously or secondary to abdominal trauma, with transmission of forces to the uterus. It is important to note that a large amount of concealed blood can be retained between the detached placenta and uterus, and the extent of the hemorrhage may not be fully appreciated until delivery. The most significant risk factor for abruption is a history of abruption in prior pregnancies (10-fold increased risk). An increased incidence is also seen in pregnancies complicated by hypertensive disorders, including preeclampsia, eclampsia, the HELLP ( h emolysis, e levated l iver enzymes, and l ow p latelets) syndrome, and abnormal implantation of the placenta (e.g., placenta previa, accreta, increta, percreta). Smoking and cocaine use also increase the risk for abruption.

In the immediate postpartum period (first 24 hours), bleeding is usually the result of uterine atony if the uterus fails to contract. Atony is more likely to occur with conditions that overdistend the uterus, such as a large-for-gestational-age fetus, polyhydramnios, and multiparity. Prior history of postpartum hemorrhage, prolonged labor, induced labor, augmentation of labor with oxytocin, and instrumentation delivery also increase the risk of postpartum hemorrhage. After 24 hours postpartum, retained products of conception (POCs) are the most common cause of bleeding.