Pregnancy week 1

When you find out you're pregnant, one of the first things you will want to know is when your baby is due.

Your baby’s due date is actually calculated from the first day of your last period. Add nine months onto this date and then add another seven days. For example, if your last period started on 1 March, then you would calculate your due date as follows:

1 March + 9 months = 1 December

1 December + 7 days = 8 December which will be your estimated due date

It is assumed that you will actually conceive halfway between periods (on day 14 of your cycle) and that pregnancy lasts 38 weeks from the date you conceive.

This means that your 40 weeks of pregnancy also include the first two weeks of your last cycle when you weren’t actually pregnant because you hadn’t conceived yet.

Due dates are not set in stone

It is important to remember that not every woman has a 28 day cycle though, and not everyone produces an egg which is ready for fertilisation halfway between their periods. If you conceive earlier or later in your cycle then your due date will be different from that estimated.

In fact, only 5% of women have their baby on the due date calculated at the start of their pregnancy. More babies are born after their calculated due date but it is normal to have your baby up to about two weeks on either side of your due date.

What's on your mind?

Finding out you're pregnant can be exciting, scary and worrying all at the same time. NCT provides a range of articles on pregnancy and birth to help you feel supported and informed as your pregnancy progresses.