Bleeding before the expected time of menarche could be a sign of precocious puberty. Other possible causes include the presence of a foreign body in the vagina, molestation, vaginal infection (vaginitis), and rarely, a tumor.

The bleeding is usually light, often referred to as "spotting," though a few women may experience heavier bleeding.

Many women find that the breakthrough bleeding ceases after one or two cycles.

Most unusual bleeding or irregular bleeding (metrorrhagia) in premenopausal women is caused by changes in the hormonal balance of the body. These changes are not pathological. Exceptionally heavy bleeding during menstruation is termed "menorrhagia" or "hypermenorrhea", while light bleeding is called "hypomenorrhea". Women on hormonal contraceptives can experience breakthrough bleeding and/or withdrawal bleeding. Withdrawal bleeding occurs when a hormonal contraceptive or other hormonal intake is discontinued.

There are pathological causes of unusual vaginal bleeding as well. Dysfunctional uterine bleeding is a common cause of menorrhagia and irregular bleeding. It is due to a hormonal imbalance, and symptoms can be managed by use of hormonal contraception (although hormonal contraception does not treat the underlying cause of the imbalance). If it is due to polycystic ovary syndrome, weight loss may help, and infertility may respond to clomifene citrate. Uterine fibroids (leiomyoma) are benign tumors of the uterus that cause bleeding and pelvic pain in approximately 30% of affected women. Adenomyosis, a condition in which the endometrial glands grow into the uterine muscle, can cause dysmenorrhea and menorrhagia. Cervical cancer may occur at premenopausal age, and often presents with "contact bleeding" (e.g. after sexual intercourse). Uterine cancer leads to irregular and often prolonged bleeding. In recently pregnant women who have delivered or who have had a miscarriage, vaginal bleeding may be a sign of endometritis or retained products of conception.

Gynecologic hemorrhage represents excessive bleeding of the female reproductive system. Such bleeding could be visible or external, namely bleeding from the vagina, or it could be internal into the pelvic cavity or form a hematoma. Normal menstruation is not considered a gynecologic hemorrhage, as it is not excessive. Hemorrhage associated with a pregnant state or during delivery is an obstetrical hemorrhage.

Signs and symptoms may initially include: an increased heart rate, feeling faint upon standing, and an increased breath rate. As more blood is lost the women may feel cold, their blood pressure may drop, and they may become unconscious.

Menstruation occurs typically monthly, lasts 3–7 days, and involves up to 80 ml blood. Bleeding in excess of this norm in a nonpregnant woman constitutes gynecologic hemorrhage. In addition, early pregnancy bleeding has sometimes been included as gynecologic hemorrhage, namely bleeding from a miscarriage or an ectopic pregnancy, while it actually represents obstetrical bleeding. However, from a practical view, early pregnancy bleeding is usually handled like a gynecological hemorrhage.

A normal menstrual cycle is 21–35 days in duration, with bleeding lasting an average of 5 days and total blood flow between 25 and 80 mL. Menorrhagia is defined as total menstrual flow >80ml per cycle, or soaking a pad/tampon every 2 hours or less. Deviations in terms of frequency of menses, duration of menses, or volume of menses qualifies as abnormal uterine bleeding. Bleeding in between menses is also abnormal uterine bleeding and thus requires further evaluation.

Complications of Menorrhagia could also be the initial symptoms. Excessive bleeding can lead to anemia which presents as fatigue, shortness of breath, and weakness. Anemia can be diagnosed with a blood test.

Depending on the definition in question, postpartum hemorrhage is defined as more than 500ml following vaginal delivery or 1000ml of blood loss following caesarean section in the first 24 hours following delivery.

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.

Breakthrough bleeding (BTB) is any of various forms of vaginal bleeding, usually referring to mid-cycle bleeding in users of combined oral contraceptives, as attributed to insufficient estrogens. It may also occur with other hormonal contraceptives. Sometimes, "breakthrough bleeding" is classified as "abnormal" and thereby as a form of metrorrhagia, and sometimes it is classified as "not abnormal".

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.

Clinical symptoms of apoplexy associated with the basic mechanism of this disease:

1. Pain, which occurs primarily mid-cycle or after a minor delay in menstruation (at the time of the rupture of a corpus luteum cyst, for example). Pain is most often localized in the lower abdomen. Sometimes the pain may radiate to the rectum or to the lumbar or the umbilical region.

2. Bleeding into the abdominal cavity, which may be accompanied by:

Sometimes there may be inter-menstrual bleeding or spotting after menstruation.

Quite often, ovarian apoplexy occurs after intercourse or training in the gym, when pressure in the abdomen has increased or ovarian tissue has experienced some stress. However, rupture of ovarian tissue can occur in conjunction with other diseases.

Abnormal bleeding after delivery, or postpartum hemorrhage, is the loss of greater than 500 ml of blood following vaginal delivery, or 1000 ml of blood following cesarean section. Other definitions of excessive 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.

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

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.

However, according to recent data, this classification is inadequate, because the ovary cannot rupture without bleeding.

Therefore, a new pathology has been devised in which the condition is divided according to severity: mild, moderate and severe (depending on the magnitude of blood loss).

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.

Chorionic hematomas can be caused by the separation of the chorion from the endometrium (inner membrane of the uterus). Hematomas are classified by their location between tissue layers:

- Subchorionic hematomas, the most common type, are between the chorion and endometrium.

- Retroplacental hematomas are entirely behind the placenta and not touching the gestational sac.

- Subamniotic or preplacental hematomas are contained within amnion and chorion. Rare.

Most patients with a small subchorionic hematoma are asymptomatic. Symptoms include vaginal bleeding, abdominal pain, premature labor and threatened abortion.

Ultrasonography is the preferred method of diagnosis. A chorionic hematoma appears on ultrasound as a hypoechoic crescent adjacent to the gestational sac. The hematoma is considered small if it is under 20% of the size of the sac and large if it is over 50%.

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.

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.

Women with placenta previa often present with painless, bright red vaginal bleeding. This commonly occurs around 32 weeks of gestation, but can be as early as late mid-trimester. 51.6% of women with placenta previa have antepartum haemorrhage. This bleeding often starts mildly and may increase as the area of placental separation increases. Previa should be suspected if there is bleeding after 24 weeks of gestation. Bleeding after delivery occurs in about 22% of those affected.

Women may also present as a case of failure of engagement of fetal head.

In the early stages of placental abruption, there may be no symptoms. When symptoms develop, they tend to develop suddenly. Common symptoms include sudden-onset abdominal pain, contractions that seem continuous and do not stop, vaginal bleeding, enlarged uterus disproportionate to the gestational age of the fetus, decreased fetal movement, and decreased fetal heart rate.

Vaginal bleeding, if it occurs, may be bright red or dark.

A placental abruption caused by arterial bleeding at the center of the placenta leads to sudden development of severe symptoms and life-threatening conditions including fetal heart rate abnormalities, severe maternal hemorrhage, and disseminated intravascular coagulation (DIC). Those abruptions caused by venous bleeding at the periphery of the placenta develop more slowly and cause small amounts of bleeding, intrauterine growth restriction, and oligohydramnios (low levels of amniotic fluid).

Abnormal uterine bleeding is a general category that includes any bleeding from menstrual or nonmenstrual causes. Hypomenorrhea is abnormally light menstrual periods. Menorrhagia (meno = month, rrhagia = excessive flow/discharge) is an abnormally heavy and prolonged menstrual period. Metrorrhagia is bleeding at irregular times, especially outside the expected intervals of the menstrual cycle. If there is excessive menstrual and uterine bleeding other than that caused by menstruation, menometrorrhagia (meno = prolonged, metro = uterine, rrhagia = excessive flow/discharge) may be diagnosed. Causes may be due to abnormal blood clotting, disruption of normal hormonal regulation of periods or disorders of the endometrial lining of the uterus. Depending upon the cause, it may be associated with abnormally painful periods.

Disorders of ovulation include oligoovulation and anovulation:

- Oligoovulation is infrequent or irregular ovulation (usually defined as cycles of ≥36 days or <8 cycles a year)

- Anovulation is absence of ovulation when it would be normally expected (in a post-menarchal, premenopausal woman). Anovulation usually manifests itself as irregularity of menstrual periods, that is, unpredictable variability of intervals, duration, or bleeding. Anovulation can also cause cessation of periods (secondary amenorrhea) or excessive bleeding (dysfunctional uterine bleeding).

Hematosalpinx (sometimes also hemosalpinx) is a medical condition involving bleeding into the fallopian tubes.