Pregnancy week by week
Pick a week to see your baby's average size as a fruit or vegetable, the length and weight, what's developing, how you may feel and one practical tip.
Pregnancy is counted in about 40 weeks from the first day of your last period, in 3 trimesters. [2] Each page gives the average length for that week from the NHS, and from week 14 the average weight from the WHO fetal growth charts. [1][3]
These are averages. Every baby grows at their own pace.
Not sure which week you're in?
The due date calculator works it out from your last period or conception date.
First trimester
Week 4a poppy seed
Week 5a sesame seed
Week 6a lentil
Week 7a blueberry
Week 8a raspberry
Week 9a cherry
Week 10a strawberry
Week 11a fig
Week 12a lime
Week 13a peachSecond trimester
Week 14a lemon
Week 15an apple
Week 16an avocado
Week 17a pear
Week 18a bell pepper
Week 19a mango
Week 20a banana
Week 21a pomegranate
Week 22a papaya
Week 23a grapefruitWeek 24an ear of corn
Week 25an eggplant
Week 26a coconut
Week 27a cauliflowerThird trimester
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 40Questions
How are pregnancy weeks counted?
From the first day of your last period. Pregnancy is assumed to start about 2 weeks later, so week 4 is about 2 weeks after conception, and a pregnancy lasts about 40 weeks.
Where do the sizes come from?
Lengths are the averages the NHS gives for each week. Weights from week 14 are the middle value (50th percentile) of the WHO fetal growth charts. They are averages, so your own scans may differ.
Which trimester am I in?
ACOG counts the first trimester to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 on.
Sources
- NHS: Week-by-week guide to pregnancy Checked October 30, 2026
- ACOG: How your fetus grows during pregnancy Checked October 30, 2026
- WHO: The World Health Organization fetal growth charts (Kiserud et al., PLoS Medicine 2017), table 11: estimated fetal weight Checked October 30, 2026
Spotted an error? Write to [email protected]. How we check health information.