Week by week pregnancy calendar

pregnancy week by week calendar

Congratulations, you're pregnant! Our week-by-week guide to your pregnancy will, we hope, tell you fascinating facts about what's happening to you and your growing baby over the next nine months. From a bundle of cells to a fully formed baby, it's an extraordinary 40 weeks of development – and it's all hosted by you.

A few notes about our week-by-week pregnancy calendar:

Use the calendar at the top of each page to select your current week, or trimester, of pregnancy. You can work out how far along you are and roughly when you can expect to meet your baby using our due date calculator.

Your pregnancy is counted from the first day of your last period. Strange as it may seem, when the sperm meets the egg you're already counted as two weeks pregnant. So, when your pregnancy test is positive you'll be five or six weeks through your total of 40 without realising.

(This is good news as time can stand still when you're pregnant – especially in the home straight. Your baby, however, starts sprinting to the finish line as soon as conception occurs.)

Please remember, not all babies develop at the same time and in the same way, so what we say may not always match your own experience. If you have any worries, ask your antenatal team or GP.

These guides will sometimes tell you about what can go wrong. Thankfully, it's rare for things to go wrong, especially after week 12, so please enjoy your pregnancy and don't worry.

We all know babies come in two flavours (better known as 'boys and girls') but, as most of you won't know what flavour you're getting – or at least not yet – we'll refer to your baby as both 'he' and 'she' throughout the weeks.

pregnancy baby development week by week

Baby development illustrations are taken from The Pregnancy Encyclopedia, published by DK.