A pregnancy that goes beyond about 42 weeks can put the baby at risk because the placenta starts to degenerate. It is therefore sometimes necessary to start (induce) labour artificially. Labour may also be induced for a number of other reasons, including diseases of the mother (eg. pre-eclampsia, diabetes), and problems with the baby (eg. foetal distress from a twisted cord or separating placenta).
Induction of labour can be done in a number of ways, including rupturing the membranes that surround the baby through the vagina, stimulating the cervix, by tablets, vaginal gel (eg. dinoprostone) or by medication given through a drip into a vein in the arm. Using these methods, doctors can control the rate of labour quite accurately to ensure that there are no problems for either mother or baby.