Weeks 35 to 38
The baby continues to put on weight, reaching an average of 3.4 kilograms by 38 weeks (the 40th week of pregnancy). It is outgrowing the womb, and starts the birth off by releasing hormones. The muscles of the mother's womb start to contract, and labour begins. Most babies are born within ten days of their due date - but only 5 per cent actually arrive on the predicted day.
