Pregnancy week by week
Follow your pregnancy from 1 to 40 weeks. Each week explains your baby's size and development, changes in your body, common symptoms, a checklist, tips for your partner and when to call the doctor. Pick your week below, or work out how many weeks pregnant you are.
First trimester: weeks 1 to 13
Your baby's organs, heart and brain form, and you may feel sick and very tired. Folic acid matters most now. You'll have your booking appointment and dating scan.
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13
Second trimester: weeks 14 to 27
Energy returns, your bump shows and you'll feel your baby move. You'll have your anomaly scan at around 20 weeks and a glucose test at 24 to 28 weeks.
Week 14 Week 15 Week 16 Week 17 Week 18 Week 19 Week 20 Week 21 Week 22 Week 23 Week 24 Week 25 Week 26 Week 27
Third trimester: weeks 28 to 40
Your baby gains weight and gets ready for birth. Sleep on your side, track your baby's movements, pack your hospital bag and learn the signs of labour.
Week 28 Week 29 Week 30 Week 31 Week 32 Week 33 Week 34 Week 35 Week 36 Week 37 Week 38 Week 39 Week 40
How big is my baby?
| Week | About the size of |
|---|---|
| 4 weeks | a poppy seed |
| 8 weeks | a raspberry |
| 12 weeks | a lime |
| 16 weeks | an avocado |
| 20 weeks | a banana |
| 24 weeks | a corn cob |
| 28 weeks | an aubergine |
| 32 weeks | a squash |
| 36 weeks | a large papaya |
| 40 weeks | a watermelon |
Prefer months? See pregnancy month by month.
Questions about pregnancy weeks
How many weeks is a full-term pregnancy?
A full-term pregnancy is counted as 40 weeks from the first day of your last period. Babies born between 37 and 42 weeks are considered term, and full term is 39 to 40 weeks.
When does each trimester start?
The first trimester runs from week 1 to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth.
Why does the guide start at week 4?
Weeks 1 and 2 are counted from your last period, before you conceive, and implantation happens around week 4. Most women find out they are pregnant at about 4 or 5 weeks.