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Obstetrical bleeding also known as obstetrical hemorrhage and maternal hemorrhage, refers to heavy bleeding during pregnancy, labor, or the postpartum period. Bleeding may be vaginal or less commonly but more dangerously, internal, into the abdominal cavity. Typically bleeding is related to the pregnancy itself, but some forms of bleeding are caused by other events.

The most frequent cause of maternal mortality worldwide is severe hemorrhage with 8.7 million cases occurring in 2015 and 83,000 of those events resulting in maternal death. Between 2003 and 2009, hemorrhage accounted for 27.1% of all maternal deaths globally.

Early pregnancy
In ICD-10, early pregnancy bleeding (code O20.9) refers to obstetrical hemorrhage before 20 completed weeks of gestational age.

First trimester bleeding, is obstetrical hemorrhage in the first trimester (0 weeks-12 weeks of gestational age). First trimester bleeding is a common occurrence and estimated to occur in approximately 25% of all (clinically recognized) pregnancies.

First trimester bleeding, is obstetrical hemorrhage in the first trimester (0 weeks-12 weeks of gestational age). First trimester bleeding is a common occurrence and estimated to occur in approximately 25% of all (clinically recognized) pregnancies.[5][6]

Differential diagnosis of first trimester bleeding is as follows, with the mnemonic AGE IS Low (during first trimester):
 * Abortion (spontaneous), also referred to as miscarriage. One study came to the result that the risk of miscarriage during the course of the pregnancy with just spotting during the first trimester was 9%, and with light bleeding 12%, compared to 12% in pregnancies without any first trimester bleeding. However, heavy first trimester bleeding was estimated to have a miscarriage risk of 24%.
 * Gestational trophoblastic neoplasia
 * Ectopic pregnancy, which implies a pregnancy outside the uterus, commonly in the fallopian tube, and may lead to bleeding, internally, that could be fatal if untreated. In cases where there is a heavy bleeding and an obstetric ultrasonography comes to the result of pregnancy of unknown location (no visible intrauterine pregnancy), it has been estimated that approximately 6% have an underlying ectopic pregnancy.
 * Implantation bleeding
 * Chorionic hematoma
 * Spotting
 * Lower GU tract causes
 * Vaginal bleed
 * Cervical bleed

Other causes of early pregnancy bleeding may include:
 * Postcoital bleeding, which is vaginal bleeding after sexual intercourse that can be normal with pregnancy
 * Iatrogenic causes, or bleeding due to medical treatment or intervention, such as sex steroids, anticoagulants, or intrauterine contraceptive devices


 * Infection

Later pregnancy
Main article: Antepartum bleeding

Antepartum bleeding (APH), also prepartum hemorrhage, is bleeding during pregnancy from the 24th week  (sometimes defined as from the 20th week ) gestational age to term (40th week). The primary consideration is the presence of a placenta previa which is a low lying placenta at or very near to the internal cervical os. This condition occurs in roughly 4 out of 1000 pregnancies and usually needs to be resolved by delivering the baby via cesarean section. Also a placental abruption (in which there is premature separation of the placenta) can lead to obstetrical hemorrhage, sometimes concealed. This pathology is of important consideration after maternal trauma such as a motor vehicle accident or fall.

Other considerations to include when assessing antepartum bleeding are: sterile vaginal exams that are performed in order to assess dilation of the patient when the 40th week is approaching. As well as cervical insufficiency defined as a midtrimester (14th-26th week) dilation of the cervix which may need medical intervention to assist in keeping the pregnancy sustainable.

During labor
Besides placenta previa and placental abruption, uterine rupture can occur, which is a very serious condition leading to internal or external bleeding. Bleeding from the fetus is rare, but may occur with two conditions called vasa previa and velamentous umbilical cord insertion where the fetal blood vessels lie near the placental insertion site unprotected by Wharton's jelly of the cord. Occasionally this condition can be diagnosed by ultrasound. There are also tests to differentiate maternal blood from fetal blood which can help in determining the source of the bleed.

After delivery
Main article: Postpartum bleeding

Bleeding after delivery, or postpartum bleeding, is the loss of greater than 500 ml of blood following vaginal delivery, or 1000 ml of blood following cesarean section. Other definitions of postpartum bleeding are hemodynamic instability, drop of hemoglobin of more than 10%, or requiring blood transfusion. In the literature, primary postpartum hemorrhage is defined as uncontrolled bleeding that occurs in the first 24 hours after delivery while secondary hemorrhage occurs between 24 hours and six weeks.

Risk factors
In rare cases, inherited bleeding disorders, like hemophilia, von Willebrand disease (vWD), or factor IX or XI deficiency, may cause severe postpartum hemorrhage, with an increased risk of death particularly in the postpartum period. The risk of postpartum hemorrhage in patients with vWD and carriers of hemophilia has been found to be 18.5% and 22% respectively. This pathology occurs due to the normal physiological drop in maternal clotting factors after delivery which greatly increases the risk of secondary postpartum hemorrhage.

Another bleeding risk factor is thrombocytopenia, or decreased platelet levels, which is the most common hematological change associated with pregnancy induced hypertension. If platelet counts drop less than 100,000 per microliter the patient will be at a severe risk for inability to clot during and after delivery.

Medical tests
If a small amount of bleeding is seen in early pregnancy a physician may request:
 * A quantitative human chorionic gonadotropin (hCG) blood test to confirm the pregnancy or assist in diagnosing a potential miscarriage
 * Transvaginal pelvic ultrasonography to confirm that the pregnancy is not outside of the uterus
 * Blood type and Rh test to rule out hemolytic disease of the newborn

For bleeding seen in later pregnancy tests may include:
 * Complete blood count (CBC) and blood type and screen
 * Ultrasound to determine placental location
 * Kleihauer-Betke (KB) test especially if there was maternal trauma

Unrelated bleeding
Pregnant patients may have bleeding from the reproductive tract due to trauma, including sexual trauma, neoplasm, most commonly cervical cancer, and hematologic disorders. Molar pregnancy also called hydatiform mole is a type of pregnancy where the sperm and the egg have joined within the uterus but instead of making an embryo it creates a cyst resembling a grape-like cluster. Bleeding can be an early sign of this tumor developing.