normal delivery time?

The length of a normal pregnancy can be anything from 37 weeks to 42 weeks. So you have a five-week period when your baby could arrive at any time and it would be considered normal.

If you give birth before 37 weeks of pregnancy, your baby is defined as premature and is likely to need extra care. A pregnancy that lasts longer than 42 weeks is called a prolonged pregnancy and may carry a higher risk of complications.

Even though all pregnant women are given a due date or estimated date of delivery (EDD), only about one in 25 babies are born on their exact due date.

Most babies arrive between 37 weeks and 41 weeks of pregnancy, usually within a week either side of their due date. Twins and particularly triplets are more likely to be born premature.

The due date you are given at your dating scan will be more accurate than using your last period to calculate it. The day of ovulation in the menstrual cycle can vary from woman to woman depending on their cycle length, while a scan can pinpoint the exact week and day of pregnancy based on the size of the embryo.

The length of your pregnancy may also be influenced by how long your baby took to implant when she was conceived. Fertilised eggs that take longer to implant tend to have a longer gestation from implantation to birth.

Mothers with naturally longer pregnancies also tend to be older, have had longer pregnancies in previous births and have been heavier at birth than mothers with shorter pregnancies.

Tall women tend to have longer pregnancies than short women, and white European women tend to have naturally longer pregnancies than African-Caribbean or Asian women.

It's common for babies to arrive a week or so after their due date. About one in five babies are born at 41 weeks of pregnancy or more.

It's thought that between one in 10 and one in 20 women has a pregnancy that would naturally last longer than 42 weeks. Although most women in the UK have their labour induced before they get to this point.