🤰 Third trimester
40 weeks pregnant
Your baby is about the size of a small pumpkin
By Emma Whitfield · Pregnancy & Baby Writer
Your baby at 40 weeks
Your due date. The average newborn is around 51cm and 3.5kg, but there's a wide healthy range. The baby is ready to meet you — birth happens when they and your body are ready.
Your body at 40 weeks
Going past your due date is completely normal. Your midwife will discuss monitoring and, if needed, options for induction, usually offered around 41–42 weeks.
Common symptoms this week
- Due date arrives (only ~1 in 20 babies come on theirs)
- Pressure, tightenings and impatience
Symptom lists are typical, never exhaustive — and having none of them is normal too.
Focus this week
Discuss what happens if you go overdue with your midwife — you may be offered a membrane sweep from around now to help things along naturally.
Week 40 checklist
- Attend your 40-week appointment (first babies)
- Consider the membrane sweep if offered
- Ask your unit how post-dates monitoring works
40 weeks pregnant: common questions
What is a membrane sweep?
A midwife sweeps a finger around the cervix during an internal examination to separate the membranes, releasing hormones that can trigger labour — offered from around 40 weeks (sometimes 39 for second babies). It's brief, can be uncomfortable, and makes labour within 48 hours more likely for many.
How big is my baby at 40 weeks pregnant?
At 40 weeks, your baby is approximately the size of a small pumpkin, about 51.2cm and around 3500g. These are approximate averages — every baby grows at its own pace.
What's happening at 40 weeks pregnant?
Your due date. The average newborn is around 51cm and 3.5kg, but there's a wide healthy range. The baby is ready to meet you — birth happens when they and your body are ready. For you: going past your due date is completely normal. your midwife will discuss monitoring and, if needed, options for induction, usually offered around 41–42 weeks.
Which trimester is 40 weeks?
40 weeks pregnant is in the third trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night. Reviewed July 2026.