Expulsion of a FETUS before it is normally viable, usually before 24 weeks of pregnancy. (Although there are exceptional cases in which fetuses as young as 22 weeks’ gestation may survive.) (See also PREGNANCY AND LABOUR.)
Usually called miscarriage by most people, 85 per cent occur in the first 12 weeks of pregnancy. Of all diagnosed pregnancies, 25 per cent end in spontaneous abortion.
Spontaneous abortions occurring in early pregnancy are almost always associated with chromosomal abnormalities of the fetus. Other causes include an anatomically malformed uterus, maternal disorders such as DIABETES MELLITUS, diseases of the thyroid gland (see under ENDOCRINE GLANDS), and problems with the immune system (see IMMUNITY). Recurrent spontaneous abortion (that is, three or more) may be a particular problem in women who have an abnormal response of their immune system to pregnancy. Other factors include being older, having had a lot of babies previously, cigarette smoking and spontaneous (but not therapeutic) abortion in the past.
Early ULTRASOUND scans have altered the management of spontaneous abortions. These make it possible to distinguish between threatened abortion, where a woman has had some vaginal bleeding but the fetus is alive; inevitable abortion, where the neck of the uterus has started to open up; incomplete abortion, where part of the fetus or placenta is lost but some remains inside the uterus; and complete abortion. There is no evidence that bed rest is effective in stopping a threatened abortion becoming inevitable.
Inevitable or incomplete abortion will usually require a gynaecologist to empty (evacuate) the uterus. (Complete miscarriage requires no treatment.) Evacuation of the uterus is carried out using local or general anaesthetic, usually gentle dilatation of the neck of the uterus (cervix), and curetting-out the remaining products of the pregnancy. (See also CURETTE.)
A few late abortions are associated with the cervix opening too early, structural abnormalities of the uterus, and possibly infection in the mother.
In proven cases of cervical incompetence, an obstetrician may recommend the cervix is closed with a suture which is removed at 37 weeks’ gestation.
In the UK, before an abortion procedure is legally permitted, two doctors must agree and sign a form defined under the 1967 Abortion Act that the continuation of the pregnancy would involve risk – greater than if the pregnancy were terminated – of injury to the physical and/or mental health of the mother or any existing child(ren).
Legislation in 1990 modified the Act, which had previously stated that, at the time of the abortion, the pregnancy should not have exceeded the 24th week. Now, an abortion may legally be performed if continuing the pregnancy would risk the woman's life, or the mental health of the woman or her existing child(ren) is at risk, or if there is a substantial risk of serious handicap to the baby. In 95 per cent of therapeutic terminations in the UK the reason given is ‘risk of injury to the physical or mental health of the woman’.
There is no time limit on therapeutic abortion where the termination is done to save the mother's life, there is substantial risk of serious fetal handicap, or of grave permanent injury to the health of the mother.
About 185,000 terminations are carried out in the UK each year, the number having fallen from a previous level of about 205,000; only 1–1.5 per cent are over 20 weeks’ gestation; the vast majority of these late abortions are for severe, late-diagnosed, fetal abnormality. In 2014, nearly 16 abortions were carried out for every 1000 women aged 15–44.
The maternal mortality from therapeutic abortion is less than 1 per 100,000 women and, provided that the procedure is performed skilfully by experienced doctors before 12 weeks of pregnancy, it is very safe. There is no evidence that therapeutic abortion is associated with any reduction in future fertility, increased rates of spontaneous abortion or preterm birth in subsequent pregnancies.
In the UK, all abortions must be carried out in premises licensed for doing so or in NHS hospitals. In 2014, 98 per cent were conducted by the NHS. About half are performed surgically and half by using medication, the latter being used more and the former less as time goes on. Proper consent must be obtained, signed for and witnessed. A woman under 16 years of age can consent to termination provided that the doctors obtaining the consent are sure she clearly understands the procedure and its implications. Parental consent in the under-16s is not legally required, but counselling doctors have a duty to advise young people to inform their parents and to record that they have given this advice. However, many youngsters do not do so. The woman's partner has no legal say in the decision to terminate her pregnancy.
A combination of two drugs, mifepristone and a prostaglandin (or a prostaglandin-like drug, misoprostol see PROSTAGLANDINS) may be used to terminate a pregnancy up to 63 days’ gestation. A similar regime can be used between nine and 12 weeks but at this gestation there is a 5 per cent risk of post-treatment HAEMORRHAGE.
An ultrasound scan is first done to confirm pregnancy and gestation. The sac containing the developing placenta and fetus must be in the uterus; the woman must be under 35 years of age if she is a moderate smoker, but can be over 35 if she is a non-smoker. Reasons for not using this method include women with diseases of the ADRENAL GLANDS, on long-term CORTICOSTEROIDS, and those who have a haemorrhagic disorder or who are on ANTICOAGULANTS. The drugs cannot be used in women with severe liver or kidney disease, and caution is required in those with CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD), disease of the cardiovascular system, or prosthetic heart valves (see PROSTHESIS), as well as with those who have had a CAESAREAN SECTION or an ECTOPIC PREGNANCY in the past or who are being treated for HYPERTENSION.
Vacuum curettage is a method used up to 14–15 weeks. Some very experienced gynaecologists will perform abortions surgically by dilating the cervix and evacuating the uterine contents up to 22 weeks’ gestation. The greater the size of the pregnancy, the higher the risk of haemorrhage and perforation of the uterus. In the UK, illegal abortion is rare but in other countries this is not the case. Where illegal abortions are done, the risks of infection and perforation are high and death a definite risk.