The spontaneous end of a pregnancy before week 24, also known as a spontaneous abortion
- Most common under the age of 16 and over the age of 35
- In some cases, due to a genetic or chromosomal abnormality in the fetus
- Smoking and alcohol or drug abuse during pregnancy are risk factors
More than 1 in 4 of all pregnancies end in miscarriage, the loss of a fetus before the 24th week of pregnancy. Most miscarriages occur in the first 14 weeks of pregnancy, and some occur so early that the woman may not be aware that she is pregnant. Generally, women who miscarry have abnormal vaginal bleeding and abdominal cramps.
What are the causes?
About 3 in 5 miscarriages in the first 14 weeks of pregnancy are caused by a genetic disorder or an abnormality in the fetus. Early miscarriage is more common in multiple pregnancies (see Multiple pregnancy and its problems).
Later miscarriages (between weeks 14 and 24) may be due to a weak cervix (see Cervical incompetence) or to a severe infection in the mother. An abnormally shaped uterus or noncancerous tumours in the wall of the uterus (see Fibroids) may also cause a late miscarriage. Smoking and alcohol or drug abuse in pregnancy are also risk factors. Women who have diabetes mellitus are at increased risk of a late miscarriage.
Any of the above factors may cause recurrent miscarriages. Generally, miscarriage is more common in women under the age of 16 or over 35. It is a commonly held belief that stress or minor injuries may lead to miscarriage, but there is no evidence to support this.
What are the types?
A miscarriage can be classified into one of several different types: threatened, inevitable, and missed miscarriage.
In a threatened miscarriage, the fetus is alive and the cervix remains closed. There is some vaginal bleeding, which is usually painless, but the pregnancy often continues for its full term of about 40 weeks. However, sometimes a threatened miscarriage develops into an inevitable miscarriage.
In an inevitable miscarriage, the fetus is usually dead and the cervix is open. An inevitable miscarriage is frequently painful because the uterus contracts to expel the fetus. Pain varies from mild, menstrual period-type pains to severe pain, and there may be heavy vaginal bleeding with clots. An inevitable miscarriage may be either complete (all the contents of the uterus are expelled) or incomplete (some contents remain in the uterus after the miscarriage).
In a missed miscarriage, the fetus is dead, but there is usually no bleeding or pain. The uterus does not contract, and the cervix is closed with the fetus still inside. Although pregnancy symptoms, such as nausea, come to an end, a missed miscarriage is often not detected until a routine ultrasound scan is carried out (see Ultrasound scanning in pregnancy).
You should consult your doctor if you have vaginal bleeding or pain in pregnancy. If bleeding or pain is severe, call an ambulance immediately.
How is it diagnosed?
Your doctor will examine your cervix using a speculum. If your cervix is closed, an ultrasound scan will be performed and, if the fetus is alive, the pregnancy often continues. However, if the cervix is open, miscarriage is usually inevitable. An ultrasound scan will be carried out to check that all the contents of the uterus have been expelled.
How might the doctor treat it?
If you have a threatened miscarriage, your doctor will probably suggest that you rest for a few days until the bleeding has stopped and any identifiable cause, such as an infection, is treated. In the event of an inevitable miscarriage, your treatment will depend on whether the miscarriage is complete or incomplete. Normally, no further medical treatment is needed for a complete miscarriage, although you may be given painkillers if necessary. If a miscarriage was incomplete, you may need to be admitted to hospital so that any tissue left behind in the uterus can be removed. This procedure is also used for an early missed miscarriage. The doctor may also prescribe antibiotics to prevent an infection developing. If a missed miscarriage occurs in later pregnancy, you may require induction of labour.
What can I do?
The loss of a baby is always distressing, and you should take time to grieve and talk about your feelings. You may want to discuss your concerns about future pregnancies with your doctor. If you want to become pregnant again, it is best to wait several months to give yourself time to recover from your loss.
What is the prognosis?
Most women who have a miscarriage do not have problems with subsequent pregnancies. Some women have recurrent miscarriages, but with specialist investigation and treatment they may eventually have a successful pregnancy.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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