Mother nature rules is an important factor.If contraception has been via 'the pill' and for some time [more than 3 years] this has been telling the body that pregnancy is not wanted.Hormonal balances have been disrupted and reset.Also age,[yawn] is important-nature has hard wired the system for conception to be best from 15 to 35.Thus when contraception pills are not taken it can be 6 months before hormonal balances are restored and the body says to itself ahhhh switch back to fertility and pregnancy.Other methods of contraception still affect natures systems but noone shold think that after years of 'switching off' the body will respond quickly for a pregnancy.