DATA BRIEFING: Caesarean rates in one part of the UK have now reached the US average - and every 1 per cent rise costs the NHS £5m, says John Appleby

Choice in childbirth is, everyone would agree, a good thing. Choices facing women and their partners include where to give birth, who should attend, the extent of invasive monitoring of the baby, and the type of pain relief used. Some choices concern personal preferences, but others - whether or not to have a caesarean section, for example - affect healthcare staff. Moreover, the choice of a caesarean means weighing up complicated information about risks and benefits. And for an individual mother and baby, it involves a difficult translation of trial results to their particular circumstances, characteristics and preferences.

This last point is sometimes overlooked by doctors;

patients often place a different value on costs and benefits than do healthcare professionals. In the case of a birth there are a number of potential outcome measures which may be more or less important to mothers. The successful delivery of a healthy baby is the most important outcome, but mothers will also want to take into account the degree of pain associated with different ways of giving birth, and the risks of various morbidities to themselves - perineal tearing, subsequent stress incontinence, etc. Mothers will also want to take account not only of outcomes, but process measures too; some will value the presence of a birth partner, others may not.

Weighing up and trading off these many outcome and process measures is difficult, and the stakes for mothers and babies and for medical staff - can be high.

Concerns about growing trends in the caesarean section rate, not only in this country, but around the world, have been expressed for 20 years or more. The most recent figures for England show that rates are now around 19 per cent of all births - with rates in London now equivalent to the average for the US (21 per cent). It is estimated that each 1 per cent increase in the caesarean-section rate costs the NHS£5m. In Brazil, the Ministry of Health has imposed a ceiling of 35 per cent for the caesarean rate; in private hospitals, 70 per cent of births are now caesarean. The most quoted optimal rate is the World Health Organisation's 10-15 per cent.

While it seems that more women are choosing caesareans (indeed, one survey reported that 31 per cent of female obstetricians would choose an elective caesarean) the risks of maternal death where there is no emergency are 2. 84 times higher with a caesarean than with a vaginal birth. Moreover, babies born by caesarean - again, where there are no complications - are at risk of respiratory distress syndrome.

As with virtually all medical interventions, decisions involve balancing risks. For a baby in distress the potential risks of a caesarean can be outweighed by the risks of not doing it. Ironically, one indication for caesarean - breech presentation for a first baby - may well become increasingly self-fulfilling: as more caesareans are carried out for this reason, midwives and obstetricians will slowly lose experience and skills in delivering breech babies.