Prematurity is officially defined as any infant born at less than 37 weeks gestation. The baby is also called pre-term, because it’s arrived before the pregnancy has come to term. In most cases the reason why babies arrive early is unknown, but premature labour is associated with some other conditions of pregnancy such as pre-eclampsia and polyhydramnios (described in this section), multiple pregnancy or infection. Any abnormality in the uterus such as fibroids or incompetence of the cervix can precipitate early delivery, and it occurs more often in women who smoke, are relatively malnourished, have a history of early delivery and who have frequent pregnancies. Premature babies are smaller than they should be, and are at risk of developing complications - with the risks being greater the smaller and earlier they are. (some babies are small even though the pregnancy has continued to 40 weeks. These babies are called light for dates, and while this may be a result of foetal malformation it is more usually a result of intra-uterine growth delay, described above). The major problems associated with birth before 32 weeks gestation are lack of surfactant - the wetting agent that allows the lungs to expand - and low blood sugar. Premature labour can sometimes be stopped using agents which prevent uterine contraction. Women who go into labour early need expert assistance.