Miscarriage is the most common kind of pregnancy loss, affecting around one in four pregnancies. This section of our website aims to tell you something about what it is, why it happens and more.
We talk below about what miscarriage is and what we know about its causes. On the pages that follow, we’ll talk about
- symptoms and diagnosis
- the physical process
- what happens after miscarriage
- tests and treatments
- missed miscarriage
- late (second trimester) miscarriage, and
- recurrent miscarriage.
We hope this will help at what can be a very difficult time.
What is a miscarriage?
Miscarriage is when a baby (or fetus or embryo) dies in the uterus during pregnancy. In the UK, that definition applies to pregnancies up to 23 weeks and 6 days, and any loss from 24 weeks is called a stillbirth. If the baby is born alive, even before 24 weeks, and lives even for a matter of minutes, that is considered a live birth and a neonatal death.
Those are legal timelines and definitions but you might feel that they don’t fit your circumstances, perhaps especially if your baby died late in pregnancy but before 24 weeks. It can be upsetting, too, because you can’t register a miscarriage. We talk more about that here.
It’s worth knowing that those definitions vary in different countries.
Why do miscarriages happen?
Even though miscarriage is so common, there’s a lot we still don’t know about why it happens. That means that most women never find out the cause of their loss, even if they have investigations.
It can be very difficult to cope with not having an obvious reason for your miscarriage. If you know why it happened, that can help make sense of it all, and perhaps help you plan for another pregnancy. If you don’t know, you may begin to wonder whether it was somehow your or your partner’s fault.
Causes of miscarriage
The main causes of miscarriage are thought to be:
- Genetic: This is when the baby doesn’t develop normally right from the start and cannot survive. This is the cause of more than half of all early miscarriages.
- Hormonal: Women with very irregular periods may find it harder to get pregnant; and when they do, are more likely to miscarry.
- Blood-clotting problems: Problems in the blood vessels that supply the placenta can lead to miscarriage, especially if the blood clots more than it should.
- Infection: Minor infections like coughs and colds are not harmful. But very high fevers and some illnesses or infections, such as German measles, may cause miscarriage.
- Anatomical: There are three main anatomical causes of miscarriage:
- If the cervix (the bottom of the uterus) is weak, it may start to open as the uterus becomes heavier in later pregnancy and this can cause a miscarriage.
- If the uterus has an irregular shape, there may not be enough room for the baby to grow.
- Large fibroids (harmless growths in the uterus) may cause miscarriage in later pregnancy.
Miscarriage isn’t just about facts, though. We know that for many women and their partners, it can be a very difficult and distressing experience and often quite a lonely one too. We talk more about this aspect of miscarriage here.
You can find more information about causes in our leaflet Why me? and we have links to several more leaflets below.
If you can’t find what you’re looking for, do contact us. We’ll always do our best to help.