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.

Women with a bleeding disorder may be prone to more excessive bleeding. A hematologic work-up should discover the cause.

Antepartum bleeding (APH), also prepartum hemorrhage, is bleeding during pregnancy from the 24th week (sometimes defined as from the 20th week) gestational age to full 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.

Vaginal bleeding occurs during 15-25% of first trimester pregnancies. Of these, half go on to miscarry and half bring the fetus to term. There are a number of causes including rupture of a small vein on the outer rim of the placenta. It can also herald a miscarriage or ectopic pregnancy, which is why urgent ultrasound is required to separate the two causes. Bleeding in early pregnancy may be a sign of a threatened or incomplete miscarriage.

In the second or third trimester a placenta previa (a placenta partially or completely overlying the cervix) may bleed quite severely. Placental abruption is often associated with uterine bleeding as well as uterine pain.

Methods of measuring blood loss associated with childbirth vary, complicating comparison of prevalence rates. A systematic review reported the highest rates of PPH in Africa (27.5%), and the lowest in Oceania (7.2%), with an overall rate globally of 10.8%. The rate in both Europe and North America was around 13%. The rate is higher for multiple pregnancies (32.4% compared with 10.6% for singletons), and for first-time mothers (12.9% compared with 10.0% for women in subsequent pregnancies). The overall rate of severe PPH (>1000 ml) was much lower at an overall rate of 2.8%, again with the highest rate in Africa (5.1%).

Anovulation is a common cause of gynecological hemorrhage. Under the influence of estrogen the endometrium (uterine lining) is stimulated and eventually such lining will be shed off (estrogen breakthrough bleeding). The anovulation chapter discusses its multiple possible causes. Longstanding anovulation can also lead to endometrial hyperplasia and facilitate the development of endometrial cancer.

Breakthrough bleeding that does not resolve on its own is a common reason for women to switch to different pill formulations, or to switch to a non-hormonal method of birth control.

Endometrial atrophy, uterine fibroids, and endometrial cancer are common causes of postmenopausal vaginal bleeding.

The presence of subchorionic bleeding around the gestational sac does not have a significant association with miscarriage overall. However, the case of intrauterine hematoma observed before 9 weeks of gestational age has been associated with an increased risk of miscarriage. In one study women who complied with instructions for bed rest for the duration of bleeding had a lower rate of miscarriage and a higher rate of term pregnancy than non-compliant women. The study had several limitations; results were severely confounded by inherent differences between compliant and non-compliant women.

Causes of postpartum hemorrhage are uterine atony, trauma, retained placenta, and coagulopathy, commonly referred to as the "four Ts":

- Tone: uterine atony is the inability of the uterus to contract and may lead to continuous bleeding. Retained placental tissue and infection may contribute to uterine atony. Uterine atony is the most common cause of postpartum hemorrhage.

- Trauma: Injury to the birth canal which includes the uterus, cervix, vagina and the perineum which can happen even if the delivery is monitored properly. The bleeding is substantial as all these organs become more vascular during pregnancy.

- Tissue: retention of tissue from the placenta or fetus may lead to bleeding.

- Thrombin: a bleeding disorder occurs when there is a failure of clotting, such as with diseases known as coagulopathies.

Breakthrough bleeding is most commonly caused by an excessively thick endometrium (uterine lining). This is not a dangerous condition, though the unpredictable and often lengthy periods of bleeding are unpleasant. Breakthrough bleeding may also be caused by hormonal effects of ovulation. Breakthrough bleeding may also itself be a symptom of pregnancy.

Breakthrough bleeding is most common when a woman first begins taking oral contraceptives, or changes from one particular oral contraceptive to another, though it is possible for breakthrough bleeding to happen at any time. Smokers are especially prone to breakthrough bleeding while taking oral contraceptives; though many users experience breakthrough bleeding in the first three cycles of taking the pill, non-smokers tend to see the bleeding dissipate more quickly than smokers.

Breakthrough bleeding is likely due to hormonal fluctuations. The body is programmed to make certain estrogen levels each day and the estrogen (and some additional hormones, such as FSH, LH, and Progesterone) are responsible for regulating endometrium shedding. Therefore, when new levels of hormones enter the body through oral contraceptives, the body is provided with two ways to receive estrogen. These excess estrogen levels can cause pre-period bleeding (bleeding through). This should be regulated in several months.

According to "Lange Gynecology and Obstetrics", 8th edition, the most common side effect associated with OC use is breakthrough bleeding. It usually occurs during the first one or two cycles and resolves itself spontaneously. Another common problem is amenorrhea. Persistent break through bleeding and amenorrhea commonly reflect an atrophic, or thin and poorly developed, endometrium.

Use of combined estrogen and progesterone eliminates the normal endogenous hormonal cycling and gradually produces atrophy of the endometrial glands. This is because the dosage of estrogen in the OCs pills is much lower than the quantity produced naturally by the ovaries. Higher quantities produced by the ovaries induce proliferation, but low levels supplied by the pills produce atrophy but are sufficient to inhibit the endogenous secretion of the gonadotropins.

The exact chain of events that lead from an atrophic endometrium to the spotting between menses is not explained by the text. This condition may be corrected by using a pill with a higher estrogen (which will stimulate further proliferation of the endometrium) or lower progestin content (which will reduce its stability).

The following have been identified as risk factors for placenta previa:

- Previous placenta previa (recurrence rate 4–8%), caesarean delivery, myomectomy or endometrium damage caused by D&C.

- Women who are younger than 20 are at higher risk and women older than 35 are at increasing risk as they get older.

- Alcohol use during pregnancy was previous listed as a risk factor, but is discredited by this article.

- Women who have had previous pregnancies ( multiparity ), especially a large number of closely spaced pregnancies, are at higher risk due to uterine damage.

- Smoking during pregnancy; cocaine use during pregnancy

- Women with a large placentae from twins or erythroblastosis are at higher risk.

- Race is a controversial risk factor, with some studies finding that people from Asia and Africa are at higher risk and others finding no difference.

- Placental pathology (Vellamentous insertion, succinturiate lobes, bipartite i.e. bilobed placenta etc.)

- Baby is in an unusual position: breech (buttocks first) or transverse (lying horizontally across the womb).

Placenta previa is itself a risk factor of placenta accreta.

Placenta previa occurs approximately one of every 200 births. It has been suggested that incidence of placenta previa is increasing due to increased rate of Caesarian section.

Perinatal mortality rate of placenta previa is 3-4 times higher than normal pregnancies.

10% of cases occur in women who are ovulating, but progesterone secretion is prolonged because estrogen levels are low. This causes irregular shedding of the uterine lining and break-through bleeding. Some evidence has associated Ovulatory DUB with more fragile blood vessels in the uterus.

It may represent a possible endocrine dysfunction, resulting in menorrhagia or metrorrhagia.

Mid-cycle bleeding may indicate a transient estrogen decline, while late-cycle bleeding may indicate progesterone deficiency.

Menorrhagia is a menstrual period with excessively heavy flow and falls under the larger category of abnormal uterine bleeding (AUB).

Abnormal uterine bleeding can be caused by structural abnormalities in the reproductive tract, anovulation, bleeding disorders, hormone issues (such as hypothyroidism) or cancer of the reproductive tract. Initial evaluation aims at figuring out pregnancy status, menopausal status, and the source of bleeding.

Treatment depends on the cause, severity, and interference with quality of life. Initial treatment often involve contraceptive pills. Surgery can be an effective second line treatment for those women whose symptoms are not well-controlled. Approximately 53 in 1000 women are affected by AUB.

Placental abruption occurs in approximately 0.2–1% of all pregnancies. Though different causes change when abruption is most likely to occur, the majority of placental abruptions occur before 37 weeks gestation, and 14% occur before 32 weeks gestation.

Dysfunctional uterine bleeding (DUB) is abnormal genital tract bleeding based in the uterus and found in the absence of demonstrable structural or organic disease. It is usually due to hormonal disturbances: reduced levels of progesterone cause low levels of prostaglandin F2alpha and cause menorrhagia (abnormally heavy flow); increased levels of tissue plasminogen activator (TPA) (a fibrinolytic enzyme) lead to more fibrinolysis.

Diagnosis must be made by exclusion, since organic pathology must first be ruled out.

DUB can be classified as "ovulatory" or "anovulatory", depending on whether ovulation is occurring or not. It is usually a menstrual disorder, although abnormal bleeding from the uterus is possible outside menstruation.

Some sources state that the term "dysfunctional" implies a hormonal mechanism. Use of the term "abnormal uterine bleeding" is preferred in today's medicine.

Treatment depends on the type of ovary apoplexy and the severity of intra-abdominal bleeding, but the condition must be treated in a hospital. In the case of pain without signs of intraabdominal bleeding, conservative therapy may be initiated, which includes bed rest, antispasmodics, and physiotherapy. In the presence or suspected internal bleeding, surgery is indicated via laparoscopy or laparotomy. Other treatments may include efforts to stop the bleeding or resection of the affected portion of the ovary. However, in cases in which there is extensive damage to the ovary, it may be necessary to remove it.

After being discharged from the hospital, it is important to take steps to prevent a recurrence in the future. Such steps include avoiding risk factors or beginning a regimen of oral contraceptives to control ovarian activity.

The prognosis of this complication depends on whether treatment is received by the patient, on the quality of treatment, and on the severity of the abruption. Outcomes for the baby also depend on the gestational age.

In the Western world, maternal deaths due to placental abruption are rare. The fetal prognosis is worse than the maternal prognosis; approximately 12% of fetuses affected by placental abruption die. 77% of fetuses that die from placental abruption die before birth; the remainder die due to complications of preterm birth.

Without any form of medical intervention, as often happens in many parts of the world, placental abruption has a high maternal mortality rate.

Usually no causative abnormality can be identified and treatment is directed at the symptom, rather than a specific mechanism. However, there are known causes of abnormal uterine bleeding that need to be ruled out. Most common causes based on the nature of bleeding is listed below followed by the rare causes of bleeding (i.e. disorders of coagulation).

Chorionic hematoma (also chorionic hemorrhage) is the pooling of blood (hematoma) between the chorion, a membrane surrounding the embryo, and the uterine wall. It occurs in about 3.1% of all pregnancies, it is the most common sonographic abnormality and the most common cause of first trimester bleeding.

Causes include:

- acute pancreatitis, where methemalbumin formed from digested blood tracks around the abdomen from the inflamed pancreas

- bleeding from blunt abdominal trauma

- bleeding from aortic rupture

- bleeding from ruptured ectopic pregnancy

Importance of the sign is on a decline since better diagnostic modalities are now available.

In the ovaries of sexually mature women, follicles grow, and oocyte matures in them, to prepare for potential fertilization. As a menstrual cycle progresses, a dominant follicle begins to stand out, and in the middle of the menstrual cycle it reaches its maximum size of about 20mm. Then the follicle ruptures, releasing a mature egg (ovulation). The location from which the follicle emerges then forms a temporary cyst, called the corpus luteum, which produces hormones to continue the menstrual cycle and mature the uterine lining. This is the normal ovarian cycle.

In cases of dystrophic and sclerotic changes in ovarian tissue, acute and chronic inflammatory processes in the uterus, or in polycystic ovary syndrome and some other diseases, as well as the result of medication that stimulate ovulation, certain irregularities in ovulation process and corpus luteum formation occur. As a result, blood vessels in the ovary contract, become dilated, and increase intra-ovarian bleeding. As a result, a hemorrhage can occur in the corpus luteum due to the fragility of blood vessels, causing a hematoma. All this is accompanied by pain, weakness, dizziness, nausea, vomiting, pale skin, and/or fainting. If left untreated, internal bleeding may increase, creating a real threat to the health and life of the woman. Other possible causes of ovarian rupture include abdominal trauma, excessive physical stress, vigorous sexual intercourse, horseback riding, etc.

Cullen's sign is superficial edema and bruising in the subcutaneous fatty tissue around the umbilicus.

It is named for gynecologist Thomas Stephen Cullen (1869–1953), who first described the sign in ruptured ectopic pregnancy in 1916.

This sign takes 24–48 hours to appear and can predict acute pancreatitis, with mortality rising from 8–10% to 40%. It may be accompanied by Grey Turner's sign (bruising of the flank), which may then be indicative of pancreatic necrosis with retroperitoneal or intraabdominal bleeding.

A number of causes may account for a hematosalpinx, by far the most common being a tubal pregnancy. Blood may also escape into the peritoneal cavity leading to a hemoperitoneum.

A hematosalpinx can also be associated with endometriosis or tubal carcinoma. Further, if menstrual blood flow is obstructed (cryptomenorrhea), caused for instance by a transverse vaginal septum, and gets backed up it may lead to a hematosalpinx.