The operation used to deliver a baby through its mother's abdominal wall. It is performed when the risks to mother or child of vaginal delivery are thought to outweigh the problems associated with operative delivery. An elective section is one that is preplanned because of a known hazard; an emergency section is one performed urgently because a complication has developed suddenly which threatens the safety of mother or baby. One of the most common reasons for Caesarean section is ‘disproportion’ between the size of the fetal head and the maternal pelvis. Current guidelines favour a section if the baby is BREECH PRESENTATION. Other reasons include: if the placenta covers the entrance to the uterus (see PLACENTA PRAEVIA); or maternal HIV, hepatitis C or a recent first infection with genital herpes, to reduce the risk of infection of the baby. A woman who has had a Caesarean section in the past will not automatically need to have one for subsequent deliveries, so its need should be assessed anew in each pregnancy.

Rates of Caesarean section rates vary from hospital to hospital, and especially between countries, emphasising that the criteria for operative delivery are not universally agreed. The current rate in the UK is about 20 per cent. The rate has shown a steady rise in all countries over the last decade. Fear of litigation by patients is one reason for this rise, as is the uncertainty that can arise from abnormalities seen on fetal monitoring during labour, and the policy of offering choice to women, some of whom choose a section.

The operation is usually performed through a low, horizontal ‘bikini line’ incision. A general anaesthetic in a heavily pregnant woman carries increased risks, so the operation is often performed under regional – epidural or spinal – ANAESTHESIA. This also allows the mother to see her baby as soon as it is born, and the baby is not exposed to drugs used for general anaesthesia. If a general anaesthetic is needed (usually in an emergency), exposure to these agents may make the baby drowsy for some time afterwards and increases the chances of need for resuscitation at birth (a chance of 35/1,000 as opposed to 5/1,000 after vaginal delivery).

Another problem with delivery by Caesarean section is, of course, that the mother must recover from the operation whilst coping with the demands of a small baby. (See PREGNANCY AND LABOUR.) In general, a woman would spend 3–4 days in hospital after a Caesarean delivery rather than the 1–2 days usual after a vaginal delivery.