By the 32nd week of pregnancy most babies are in a head-down position in the womb. Up to 4 per cent of them, however, have their buttocks (breech) presenting at the neck of the womb. If the baby is still a breech presentation at the 34th to 35th week the obstetrician may, by external manipulation, try to turn it to the head-down position. If this is not successful, the fetus is left in the breech position. Breech deliveries are more difficult for mother and baby because the buttocks are less efficient than the head at dilating the cervix and vagina during labour. An EPISIOTOMY is usually necessary to assist delivery, and obstetric FORCEPS may also have to be applied to the baby's head. If the infant and/or the mother become unduly distressed, the obstetrician may decide to deliver the baby by CAESAREAN SECTION; some obstetricians prefer to deliver most breech-presentation babies using this method because evidence suggests it is safer for the babies. (See PREGNANCY AND LABOUR.)