1 = Spontaneous: the onset of regular contractions whether or not preceded by spontaneous rupture of the membranes

2 = Any caesarean section carried out immediately following the onset of labour, when the decision was made before labour

3 = Surgical induction by amniotomy

4 = Medical induction, including the administration of agents either orally, intravenously or intravaginally with the intention of initiating labour

5 = Combination of surgical induction and medical induction

8 = Not applicable (from 1996-97 onwards)

9 = Not known: validation error

null = Not applicable (from 1990-91 to 1994-95)