Miscarriage is, unfortunately, a common occurrence with an estimated 15 to 20% of all clinical pregnancies ending in miscarriage. Recurrent miscarriage is when three or more consecutive early (less than 12 weeks) miscarriages occur. Recurrent miscarriage is far less common and is estimated to affect 1 to 3% of couples.
Known causes of miscarriage include:
- Fetal chromosomal abnormality (up to 70% of early miscarriages)
- Parental chromosomal abnormality (up to 4% of cases)
- Antiphospholipid syndrome
- Maternal poor health (such as poorly controlled diabetes, thyroid disease and obesity)
- Maternal age (risk of miscarriage is known to increase with increasing maternal age)
- Congenital uterine abnormalities (found in 5 to 30% of women with a history of recurrent miscarriage)
- Fibroids (may be a cause of later pregnancy loss if affecting the uterine cavity)
- Inherited thrombophilias (activated protein C resistance, deficiency in protein C/S, deficiency in anti-thrombin III, hyperhomocysteinuria and prothrombin gene mutations have been associated with recurrent miscarriage)
Potential causes of recurrent miscarriage include:
- Luteal insufficiency (either insufficient progesterone production and or hCG production)
- Immunology (there is a great deal of debate about the involvement of Natural Killer cells in recurrent miscarriage. Endometrial biopsies have shown that women with recurrent miscarriage have differing numbers of decidual NK cells with fewer CD56Bright cells and more CD56Dim cells than in control women. NK cells in the blood vary hugely and there is no clear association with recurrent miscarriage)
- Thyroid Peroxidase Antibodies (have been associated with an increased prevalence of recurrent miscarriage)
- Maternal and Paternal HLA antigen conformity
It is important to assess each couple on an individual basis and the need for tests tailored accordingly.
It should be remembered that even after thorough investigation, a cause may not be identified as the cause of recurrent miscarriage is still not fully understood.
Whilst treatment of recurrent miscarriage should be evidence based, many treatments are given empirically with no clear evidence of efficacy. Empirical treatments should be safe and patients should be aware of the lack of evidence to support their effective use.
Support can be obtained from The Miscarriage Association