Reasons for Miscarriage

A pregnancy may end in miscarriage for many reasons, including a weakness in the womb or cervix, a chromosomal abnormality, viral infections, diabetes, or placental malformation. Sometimes there is no explanation for the loss of a pregnancy. Nearly all miscarriages are unexpected and are not preventable.

It is very rare for miscarriage to occur because of something you have or have not done, although many parents still feel this to be the case. For the majority of women the cause of the miscarriage will never be known, even after extensive testing. Many parents have expressed feelings of frustration and helplessness when a cause for their miscarriage cannot be found.

There are many different reasons for an early pregnancy loss. Some of these include:

  • Abnormalities with the embryo or foetus
  • Problems with implantation of the embryo in the wall of the uterus
  • Problems with the formation of the placenta
  • Hydatidiform mole or molar pregnancy
  • Abdominal surgery

While uncommon prior to 20 weeks gestation, abdominal surgery may increase uterine irritability.

  • Anembryonic pregnancy (previously known as blighted ovum)

Sometimes an egg is fertilised but does not continue to divide. A pregnancy test will be positive and a sac is formed, although there is no baby. Miscarriage usually occurs between seven and 12 weeks.

  • Any severe or poorly controlled illness

Illnesses such as hypothyroidism and diabetes, if not well controlled, may cause miscarriage, although only rarely.

  • Cervical incompetence

Cervical incompetence is where the cervix is unable to hold the contents of the uterus in place and painlessly dilates too early, usually after the 14th week of pregnancy.

  • Chromosomal defect or abnormality

The majority of chromosomal defects or abnormalities happen by chance and, in most cases, will remain unknown.

  • Direct trauma

An extremely severe, direct blow to the lower abdomen may damage the uterus and placenta.

  • Hydatidiform mole or molar pregnancy

In rare instances, the placenta develops abnormally into a mass of fluid-filled sacs. The symptoms of pregnancy exist although there is no baby. In very rare cases, a form of cancer can develop after such a pregnancy.

  • Immunological problems

Sometimes the mother’s immune system does not produce the antibodies necessary to prevent rejection of the baby.

  • Indirect trauma

Examples of indirect trauma are cardiac arrest, severe blood loss and shock.

  • Infection or virus

Infections or viruses such as listeria, toxoplasmosis, cytomegalovirus and others may lead to miscarriage.

  • Uterine abnormalities

Some women are born with an unusually shaped uterus, which can increase the chance of miscarriage.

Ectopic Pregnancy

Another cause for an early pregnancy loss might be an Ectopic pregnancy. This type of pregnancy develops most often in the fallopian tube and occasionally at other pelvic sites. This causes vaginal bleeding and severe abdominal pain. Some women are not aware they are pregnant until the ectopic pregnancy is diagnosed. If you experience these symptoms, medical advice should be sought as ectopic pregnancies can be life threatening. If you have an ectopic pregnancy, an operation is necessary to remove the pregnancy. Sometimes it is possible to save the fallopian tube, however, if it has ruptured it will be necessary to remove this as well.

Many women become concerned that they may be able to fall pregnant again with only one tube, however as women usually have two fallopian tubes, it is normally possible to become pregnant again if there are no other complications

Ask your doctor for further information why your miscarriage may have occurred.

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Last modified: 6/12/16