The spontaneous loss of a pregnancy before 20 weeks gestation is known as a miscarriage, though we don’t as yet know all of the reasons that cause a miscarriage.

However we do know that a miscarriage can sometimes be devastating for all concerned. Before looking at what causes a miscarriage, here are some facts about miscarriage that may help put things in perspective:

  • 20 to 30% of pregnancies end in miscarriage.What Causes a Miscarriage
  • Up to 75% of miscarriages take place in the first trimester (12 weeks) of pregnancy.
  • Some miscarriages occur so early that the woman may not yet be even aware that she was pregnant.
  • There is very little that a woman can do or not to do to prevent a miscarriage – working, having sex, exercising and other normal behaviors are not what causes a miscarriage.
  • We don’t yet know all of the reasons for a miscarriage, though a woman’s advanced age, certain medical conditions such as high blood pressure and diabetes, certain prescription medications, lifestyle habits of either parents and so on are known to increase risk of miscarriage.

General reasons understood for what causes a miscarriage are:

Chromosomal Abnormalities

These are thought to be the cause of up to 60% of miscarriages according to some experts. A mismatch of chromosomes from the mother and the father; when the egg and the sperm meet, can result in a miscarriage. In such miscarriages, the chances are high that a woman will go on to have a successful pregnancy and a healthy baby.

Genetic Reasons

Sometimes the genetic abnormalities that a fetus has are so severe, that life in the uterus cannot be sustained and this is what causes a miscarriage. A proper heart or brain may not have formed, and there could be other severe malformations; genetic problems that could result in a pregnancy loss.

Tissue rejection

New reasons for miscarriages are now coming to light and according to some experts, one of the reasons are Antiphospholipid antibodies. These are antibodies within the system, that attack one’s own tissue, including embryos, ejecting them and thereby causing miscarriage.

Uterine Abnormalities

Sometimes it is a physical reason such as malformations of the uterus that prevent a child being carried to term It may be necessary to use an MRI to detect such malformations and in some cases surgery could correct these problems. Sometimes it is the scarring in the uterus or an incompetent cervix that prevents a baby being carried to term.

Infections and medical conditions

Exposure to certain diseases when a woman is pregnant, such as measles can cause miscarriages. Certain bacterial infections, or infections of the urinary tract and so on may also be responsible for causing a miscarriage.

An estimated 5 to 10% women have Polycystic Ovary Syndrome (PCOS) and this is one of the reasons thought to cause miscarriages. There are hormonal imbalances that are thought to be the cause of miscarriage. Thyroid imbalances and uncontrolled diabetes are thought to create unfavorable an uterine environment which, in some cases is what causes a miscarriage.