When a miscarriage happens during a pregnancy at any stage it can be extremely distressing for a woman and her partner. However, when several miscarriages are experienced then this can be particularly devastating for those involved.
Miscarriages that occur in the first 12 weeks of pregnancy (first trimester) are known as early miscarriages, whereas those that occur from weeks 13-24 are known as late miscarriages.
Unfortunately, miscarriages are extremely common. It is thought that around 12-24% of known pregnancies end in miscarriage. The true number is likely to be much higher as many miscarriages occur before the woman realizes that she has missed a period and simply thinks that her period has arrived later than expected.
When a miscarriage happens three or more times in a row, it is called a recurrent miscarriage. Recurrent miscarriage affects 1 in 100 (1%) couples trying to have
a baby.
What are the risk factors for recurrent miscarriages?
- Maternal Age. As a woman gets older, the eggs (oocytes) that she is born with also increase in age. This means that there is a greater chance that the eggs are poorer in quality and may lead to an increased rate of chromosomal abnormalities. It is thought that chromosomal abnormalities may be the cause of 2-5% of couples who experience recurrent miscarriages.
- Previous history of miscarriages. As the number of miscarriage increases, unfortunately, the likelihood of further miscarriage also increases. After 3 successive miscarriages, the risk of further miscarriages rises to approximately 40%.
What are the causes of recurrent miscarriage?
- Recurrent early miscarriages (within the first semester) are most often due to genetic or chromosomal abnormalities.
- Antiphospholipid syndrome is an important cause of recurrent miscarriage. It is a disease that affects the blood and makes it more likely to clot than normal. This can lead to unwanted blood clots forming in blood vessels. In pregnancy, if a large blood clot (or lots of smaller blood clots) occurs in the placenta, then this can cause problems such as repeated miscarriage, stillbirth, pre-eclampsia, premature delivery and growth restriction. The risk of miscarriages due to Antiphospholipid Syndrome can be treated by taking aspirin and heparin (both types of blood thinning medication).
- Genetic problems in one of the parents sometimes do not manifest themselves until passed on to your baby. 2-5% of recurrent miscarriages are thought to be related to a chromosomal abnormality.
- A womb shape abnormality may lead to recurrent miscarriages.
- Polycystic ovaries have also been linked to recurrent miscarriages, although the link is not fully understood.
- Hormonal abnormalities. Some women, especially older women, have a deficiency in progesterone. The data available at present does not support the use of progesterone as a way of preventing miscarriages. Saying that progesterone supplementation is used in fertility clinics for this purpose, as there is data that supports its use when an artificial method has been used.
- Some vaginal infections have been associated with an increased risk of miscarriage.
- A significant proportion of cases of recurrent miscarriage remain unexplained despite the detailed investigation. Whilst this can be very frustrating for couples, the Royal College of Obstetricians (RCOG) estimate that the prognosis for a successful future pregnancy with supportive care alone is in the region of 75%.
When should a woman undergo investigations?
Many couples who have been through a miscarriage want to find out why it happened, especially if there is a cause that can be treated to improve their chances of success in their next pregnancy. Most, however, will not be offered further tests after a single miscarriage, or even two on the NHS. Although this can be frustrating and upsetting, the reason for this is that many women who have experienced 1 or 2 losses will then go on to have a healthy pregnancy next time. This suggests that their miscarriages were due to chance rather than to an underlying cause. However, once a couple has 3 or more miscarriages then the likelihood is that there is an underlying cause for the miscarriages increases.
On the NHS, some couples may be offered tests after 2 successive miscarriages if the woman is in her late 30’s or early 40’s, or if the couple has taken a very long time to conceive. A woman has a choice to undergo these investigations privately after 2 successive losses if she wishes to do so.
What investigations are available
Along with a gynaecological examination, we recommend the following:
- Blood Tests. The blood tests carried out involve testing for the blood count, clotting profile, and various clotting abnormalities that may lead to recurrent miscarriage (Antithrombin III, Factor V Leiden gene, Factor II Prothrombin gene, MTHFR gene, Fibrinogen, Lupus Anticoagulant, Protein C, Protein S, Anticardiolipin Antibodies). In addition, we carry out a chromosomal analysis.
- Infection screen. We recommend you have a swab for mycoplasma and ureaplasma along a routine swab culture.
- Ultrasound scan. This may identify fibroids, a weak or a short cervix or other structural abnormalities of the uterus that can be put right before your next pregnancy.
Your partner may also be recommended to undergo investigations, in particular when looking for chromosomal abnormalities.
If you wish to ask a question or book an appointment, please do get in touch.
