When is my baby due?
The length of pregnancy varies and only five per cent of babies arrive on their estimated date. Here you can find more information about pregnancy due dates.
Estimated date of delivery (EDD)
A due date or EDD, is needed for your NHS maternity care. Routine checks are organised around this date and will be considered when offering any treatment you or your baby might need. However, only five per cent of babies arrive on their EDD so the idea of a due date can be unhelpful.
How to work out your due date
Every woman and every pregnancy is different. The average length of time a pregnancy lasts is around nine months, but there is a wide range of dates within which labour can start within a healthy pregnancy.
It is very useful to work out your birth month as this helps you get prepared and remain confident if you have a longer pregnancy.
At the beginning of pregnancy, you will be asked for your last menstrual period (LMP) date. This is the date when your most recent menstrual period started. This data is used to generate an approximate EDD and is then adjusted after measuring the baby at an ultrasound scan at around 10 to 14 weeks into the pregnancy.
If you don't know the first day of your last period, don't worry; you can give a best guess. The important thing is to self-refer so you don't miss out on care.
Your midwife will talk about the length of your pregnancy and the gestational age of your unborn baby in weeks. Your pregnancy is described as reaching 40 weeks on your estimated delivery date. This might also be written as 40+0 which means forty weeks exactly. The day after can be written as 40+1, and so on up to 40+6 before the next week starts.