Dr Devora Lieberman - Miscarriage
Heartbreaking as it can be, pregnancy loss is not uncommon. With up to 20 per cent of pregnancies failing – often in the first trimester - miscarriage is a sad but normal part of human reproduction.
The loss of a pregnancy, at any stage, can be an extremely difficult and emotional time for many couples, particularly if it happens repeatedly or following infertility. But for the majority of women, it will be a one-off and they will go on to have successful pregnancies.
There are also lots of myths about causes of pregnancy loss and it’s important to remember that if you experience a miscarriage, it is almost certainly something that could not have been prevented and was not your fault.
I see many patients who are looking for answers after suffering two or more miscarriages. While it’s worthwhile investigating for underlying causes, in 50 per cent of cases we will not find a medical explanation. And for these couples, the likelihood of a subsequent pregnancy succeeding are not that different to the chance based on the woman’s age.
Here are answers to some of the most common questions about miscarriage.
What is miscarriage?
A miscarriage is a pregnancy that ends within the first 20 weeks. Most miscarriages happen within the first trimester and once a pregnancy reaches the 12 week mark, the risk of miscarriage falls to only two per cent.
Sometimes women will experience cramping and heavy bleeding, but for some women there are no symptoms and the fetus dies but stays in the uterus. This is known as a ‘missed’ or ‘silent’ miscarriage and women are usually given the option of having a surgical procedure or waiting for nature to take its course and for the fetus to be passed from the uterus.
How common is it?
It’s estimated that around 10 to 20 per cent of pregnancies end in miscarriage. But some studies* suggest that the actual rate of early pregnancy losses could be as high as between 60 and 75 per cent of conceptions – with the vast majority happening before a woman realises she is pregnant.However, the rate of miscarriage does increase as women get older. The risk of miscarriage among women in their early 20s is about 12 per cent. By the late 30s the risk is nearer to 25 per cent and by the age of 43 more than half of pregnancies will miscarry.**
Why does it happen?
It’s important to remember that there is almost always nothing that could have been done to prevent a pregnancy being lost and nothing that can be done to hang on to a pregnancy that is destined to end in miscarriage.The vast majority of miscarriages are unexplained, partly because they are not usually investigated until a woman has two or three in a row. But a random genetic abnormality is the most common cause of miscarriage.
About nine out of ten genetically abnormal pregnancies will not survive past the first trimester. In normal human cells there are 46 chromosomes, which contain DNA and genes. When cells have the wrong number of chromosomes, the error is known as aneuploidy – the best-known example of which is Down syndrome which is the result of having three copies of chromosome 21.
Around seven out of ten first trimester losses are caused by chromosome problems.
What is recurrent miscarriage?
While miscarriage is usually a one-time occurrence, up to one in 20 couples experience two miscarriages in a row and one in a hundred suffer three or more – this is known as recurrent miscarriage.
Some of the known causes of recurrent miscarriage are:
- Abnormalities of the uterus
- Blood clotting disorders
- Chromosome abnormalities
- Immune disorders
- Hormonal disorders
- Lifestyle factors such as smoking, alcohol and recreational drugs
When do you need to investigate?
If you have three miscarriages in a row, you will usually be referred to a specialist who may order some tests to see if there is an underlying cause. However, more than half of the time these investigations don’t find any explanation for the miscarriages – and this is good news, as it means you are likely to achieve a healthy pregnancy in the future without medical intervention.Because fertility declines and the risk of chromosome problems increases as we age, women in their mid to late 30s might be referred for investigations after two consecutive miscarriages.
What are the chances of a subsequent pregnancy being successful?
Where no cause for repeated miscarriage has been found, the risk of another pregnancy failing is similar to the age related risk of having a miscarriage.Studies suggest that a 20-year-old who has had three previous miscarriages faces a 90 per cent chance of the next pregnancy going to term, while a 30 year old with the same history has an 80 per cent chance of success. However, by the age of 45 the chance of a successful pregnancy after three miscarriages falls to 54 per cent. **
Is IVF an option?
Random chromosome problems are thought to be the cause of the majority of miscarriages – where a genetically abnormal embryo implants in the uterus, but is destined to fail. While the advice to couples will often be to keep trying, the emotional toll of repeated miscarriage can be immense.Also, the chance of chromosome errors increases as women get older.
There are now techniques available that allow scientists to screen an embryo in the lab during the IVF process and to ensure it has the correct number and sequence of chromosomes in the DNA.
The technique, known as CGH (Comparative Genome Hybridization) is usually recommended for older women who have suffered recurrent miscarriage or repeated IVF failure and can vastly improve the chances of a successful pregnancy and healthy baby.
*C Roberts and C Lowe ‘Where have all the conceptions gone?’ The Lancet 1975 i:498-499
** S Brigham et al ‘A longitudinal study of pregnancy outcome in unexplained recurrent first trimester miscarriage’ Human Reproduction, 1999, vol. 14, no. 11 : 2868-71
Devora Lieberman is one of the principal doctors in Genea's Miscarriage Management Program. Would you like to make an appointment with Dr Devora Lieberman? Fill out the form below.