Miscarriage is defined as pregnancy loss before 24 completed weeks of pregnancy. The occurrence of a miscarriage is a tragic loss for a couple trying to have a child and can be associated with significant psychological problems for the woman, their partner and family. Miscarriage is usually a single occurrence, and often followed by successful pregnancy. Recurrent miscarriage is defined as the loss of three or more consecutive pregnancies. Even after 3 consecutive losses, the chance of a successful pregnancy is over 60%. Most miscarriage occurs within the first 14 weeks of pregnancies. Maternal age and previous number of miscarriages are independent risk factors for a further miscarriage. There could be several reasons for repeated - recurrent miscarriages.
Causes of miscarriage
There are several causes of miscarriage that have been identified. These include chromosomal abnormalities, gene defects, hormonal problems, infection, immunological, uterine abnormalities, chronic maternal illness and environmental hazards.
Blood clotting (thrombophilic) disorders Inherited thrombophilias include Factor V Leiden, Factor II(prothrombin gene) mutations in the gene that codes for MTHFR, an enzyme involved in folate metabolism.
If blood clots occur in the blood vessels of the placenta, the blood flow to the baby is decreased and this can lead to either second trimester miscarriage or, if the pregnancy proceeds, to the birth of a baby that is smaller than he or she ought to be. Women with these disorders are also at risk of developing high blood pressure later in pregnancy
Chromosomal abnormalities One-off pregnancy losses can occur when the cells of the placenta and the fetus contain an abnormal number of chromosomes. Mostly the extra chromosome or the deficient chromosome is not present in the parents: instead the abnormality occurs as mature eggs or (less often) sperm cells are formed just before they are released
The miscarriage happens by chance. In most cases, there is nothing wrong with the mother or father's health and miscarriage is not likely to occur again in a later pregnancy.
The uterus and miscarriage Several abnormalities of the uterus are commonly linked to repeated pregnancy loss. Most of them can be treated with surgery.
They include:
• Congenital abnormalities. These are defects present from birth. For instance, a woman may have a uterus that is divided into two sections by a wall of tissue (septate uterus).
• Uterine fibroids (leiomyomata). Uterine fibroids are benign growths (not cancer) made up of uterine muscle tissue.
• Incompetent cervix. An incompetent cervix is one that begins to widen and open too early, in the middle of pregnancy, without any sign of pain or labor. Incompetent cervix is not a cause for recurrent first trimester losses.
Causes of miscarriage
There are several causes of miscarriage that have been identified. These include chromosomal abnormalities, gene defects, hormonal problems, infection, immunological, uterine abnormalities, chronic maternal illness and environmental hazards.
Blood clotting (thrombophilic) disorders Inherited thrombophilias include Factor V Leiden, Factor II(prothrombin gene) mutations in the gene that codes for MTHFR, an enzyme involved in folate metabolism.
If blood clots occur in the blood vessels of the placenta, the blood flow to the baby is decreased and this can lead to either second trimester miscarriage or, if the pregnancy proceeds, to the birth of a baby that is smaller than he or she ought to be. Women with these disorders are also at risk of developing high blood pressure later in pregnancy
Chromosomal abnormalities One-off pregnancy losses can occur when the cells of the placenta and the fetus contain an abnormal number of chromosomes. Mostly the extra chromosome or the deficient chromosome is not present in the parents: instead the abnormality occurs as mature eggs or (less often) sperm cells are formed just before they are released
The miscarriage happens by chance. In most cases, there is nothing wrong with the mother or father's health and miscarriage is not likely to occur again in a later pregnancy.
The uterus and miscarriage Several abnormalities of the uterus are commonly linked to repeated pregnancy loss. Most of them can be treated with surgery.
They include:
• Congenital abnormalities. These are defects present from birth. For instance, a woman may have a uterus that is divided into two sections by a wall of tissue (septate uterus).
• Uterine fibroids (leiomyomata). Uterine fibroids are benign growths (not cancer) made up of uterine muscle tissue.
• Incompetent cervix. An incompetent cervix is one that begins to widen and open too early, in the middle of pregnancy, without any sign of pain or labor. Incompetent cervix is not a cause for recurrent first trimester losses.
Hormonal disorders
1. Progesterone
Low levels of progesterone hormone are frequently found in women whose pregnancies are miscarrying.
However, low progesterone levels in early pregnancy reflect the fact that the pregnancy has not implanted successfully in the womb lining, rather than because the developing placenta is not producing enough progesterone to maintain the pregnancy. This is an important point - low progesterone is the effect not the cause of the miscarriage. This explains why giving women progesterone and/or hCG hormone injections in early pregnancy does not improve pregnancy outcome.
The exception to this is when we take advantage of the immunosuppressant effects of progesterone in women who are found to have immune problems.
2. Follicle Stimulating Hormone
Follicle stimulating hormone (FSH) drives the ovary to start growing follicles. Unfortunately, some women with a history of pregnancy loss are also found to have high FSH levels because their ovaries have become prematurely menopausal. Although rare, this is obviously a very important problem to identify. If FSH levels are high, the appropriate next step is referral to a fertility specialist.
3. The uterine lining (the endometrium)
At the present time the only way of determining the response of the endometrium at the time of implantation is to sample it and look at the histological (microscopic) evidence of the state of the tissues. An endometrial biopsy can be performed towards the end of your cycle (approximately day 26). This biopsy is no more uncomfortable than undergoing a cervical smear test. However, in order to be able to obtain the most useful information from the biopsy, it is important to know exactly the time of ovulation.
4. Polycystic ovarian syndrome
A pelvic ultrasound scan shows that many women with recurrent miscarriage have polycystic ovaries (PCO). This is a common condition, found in 25% of all women, in which there are multiple small cysts within the ovary. These cysts are not dangerous and cannot be removed as they are within the ovary.
Polycystic ovaries can sometimes be associated with a number of hormonal imbalances such as increased production of LH and testosterone. A number of carefully designed studies have shown that neither PCO nor high LH levels are a cause for recurrent miscarriages.
Infections The role that vaginal infections may play in recurrent pregnancy loss is the subject of a new field of research.
Infection may well play a role in causing late pregnancy losses (14 weeks gestation) in a small number of women but it is unlikely to be important in causing early miscarriages.
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