Blocked Menstrual Flow (Periods) Causes and Complications

There are many reasons why a young girl may not menstruate despite obvious signs of puberty and even other menstrual symptoms. From pregnancy and hormonal disturbances to drugs and even psychological stress, the menstrual cycle can be impacted to varying degrees. However, in these cases menstruation (periods) does not occur. This missed period is known as amenorrhea.

There are other instances where menstruation does occur but cannot pass out due to an obstruction. This blocked period flow is usually due to a physical obstruction often as a result of an anatomical abnormality. The menstrual blood may instead accumulate within the vagina or uterus. This occurrence can be mistaken for amenorrhea but there is a difference between a missed period and blocked menstrual blood.

What is cryptomenorrhea?

Cryptomenorrhea is the medical term for menstrual blood that is unable to exit the female body. Retained menstruation occurs when a woman has normal periods but the menstrual blood is unable to flow out due to an obstruction in the genital tract. This is also known as genital tract outflow obstruction.

The menstrual blood can accumulate usually within the vagina and this is known as hematocolpos (“hemato” referring to blood and “colpos” meaning vagina). Accumulation of menstrual blood within the uterus is known as hematometra. Sometimes the menstrual blood may enter the fallopian tubes which is referred to as hematosalpinx.

It is important to note that regular periods still occur in these conditions although it may seem like there is a missed period which is known as amenorrhea (no period). There may even be period pain and other menstrual symptoms. Genital outflow obstruction can lead to complications if left untreated. However, the necessity for treatment and type of treatment must be determined after investigation by a medical professional. In most cases, the condition may be corrected by surgery.

Blockage in the Female Reproductive Tract

A blockage in the female reproductive tract prevents menstrual blood outflow as well as the outflow of other secretions from within the female genital tract. This can be congenital or acquired. Congenital is where there is a defect present from birth. This can arise with abnormal development during fetal life. Acquired is where the problem develops during the course of life.

The lower two thirds of the vagina develop from the urogenital sinus, while the upper vagina, cervix, uterus, fallopian tubes, and ovaries develop from the Mullerian duct system. During development of the embryo, there can be a failure of the two systems to fuse vertically.

It results in cervical stenosis or atresia, vaginal atresia, transverse vaginal septum, and imperforate hymen. These malformations are rare and are usually accompanied by other abnormalities, especially related to the kidneys, urinary tract, and bones.

Causes of Blocked Menstruation

It is important to understand the process of menstruation. The ovary releases an egg cell (ovum) during the ovulation phase. The inner lining of the uterus (endometrium) becomes thicker in preparation for pregnancy. When pregnancy fails to occur then the egg cell along with the thickened endometrium that sloughs off is expelled. This expulsion is known as menstruation.

In genital tract outflow obstruction, secretions cannot exit the body of a female. The obstruction may not always be detected in early life. Young girls with genital tract outflow obstruction who have reached puberty will experience many of the symptoms of menstruation without the period. The hormonal changes that occur during the menstrual cycle may still occur as normal.


Some of the causes of vaginal problems that lead to retained menstrual blood have been discussed below. Most of these conditions are congenital in nature, meaning that it has been present from the time of birth.

1. Imperforate Hymen

Hematocolpos or accumulation of menstrual blood in the vagina occurs most frequently due to an imperforate hymen. The hymen is a membrane situated at the entrance to the vagina, which partially occludes the vaginal opening. In some cases, the hymen completely occludes the vagina, leading to retention of menstrual blood within the vagina.

This congenital (present at birth) abnormality may be detected in a newborn baby but is more frequently detected soon after menarche. Signs of puberty such as breast development will be present but the girl will present with a history of primary amenorrhea. There may be cyclic menstrual pain each month but no menstrual flow.

A painless mass may be felt at the lower abdomen, and urinary problems such as dysuria (painful urination) and frequency (frequent urination) may be reported. A quick surgical perforation of the hymen is usually advised.

2. Transverse vaginal septum

This is also a congenital condition which may block the outflow of menstrual blood. Excision of vaginal septum is the treatment of choice.

3. Severe labial adhesions

Labial adhesions usually form due to vaginal inflammation, local irritation or trauma. Childhood sexual abuse must be investigated in young girls who present with these adhesions. Surgery may be needed in severe cases.

4. Vaginal atresia and agenesis

These are congenital defects of the female reproductive system where the vagina partially or completely fails to form. Therefore the menstrual blood does not have a suitable passage to flow out. Vaginal reconstruction may be contemplated in suitable cases.

Causes of Hematometra

These are causes that affect the outflow of menstrual blood from the uterus (womb). The problem may lie in the upper vagina, cervix or uterus itself.

1. Proximal transverse vaginal septum

This is a congenital defect due to an embryological abnormality meaning that it arises during during fetal development.

2. Cervical stenosis

Stenosis is narrowing of the endocervical canal which could be due to a number of causes including trauma, recurrent vaginal infections (vaginitis), cervical cancer, menopause or exposure to radiation. It can also be congenital – present since birth.

3. Cervical atresia

With atresia, the cervical canal is absent. It is congenital and due to abnormal development in fetal life. The canal has to be surgically reconstructed.

Complications of Blocked Menstruation

Treatment is necessary for genital tract outflow obstruction. Surgery to some degree is usually required. If left untreated, the blockage of menstrual blood flow can lead to complications.

  • Retention of menstrual blood in the vagina (hematocolpos), uterus (hematometra) or in the fallopian tubes (hematosalpinx).
  • Retrograde menstruation or back flow of menstrual blood.
  • Endometriosis
  • Peritonitis
  • Urinary retention

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