40 Weeks Pregnant
Reviewed by Safi Allah Khan
Medically reviewed by: Safi Allah Khan · Written by the Momi team · Last updated 20 October 2026
Quick answer: At 40 weeks pregnant, your baby is about the size of a small pumpkin, about 51.2 cm (20.2 in) long. You're in the third trimester, in month 9, and this is the week of your due date. This week's milestone: due date week. Symptoms vary from person to person.
| Week 40 at a glance | |
|---|---|
| Trimester | Third |
| Month | 9 |
| Weeks to due date | Due date week |
| Baby's size | About the size of a small pumpkin |
| Length | About 51.2 cm (20.2 in) |
| Weight | About 3.4 kg (7.6 lb) |
| This week | Due date week |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 40 weeks
Your baby is about the size of a small pumpkin and weighs about 3.4 kg (7.6 lb), although healthy newborns vary widely. ACOG says babies are about 20 inches and 7.5 to 8 pounds at 40 weeks.
Your body at 40 weeks pregnant
You've reached your due date. Only a small share of babies arrive on this exact day. If you're still pregnant, your provider will talk about monitoring and your options, including induction.
Things to do this week
- Attend your 40-week check.
- Ask about next steps if you go past 41 weeks.
- Call straight away about reduced movements, bleeding or your waters breaking.
When to call your doctor or midwife
Contact your care team straight away if:
- your baby is moving less than usual or you can't feel them moving
- your waters break, especially if the fluid is green, brown, smelly or bloody
- you have vaginal bleeding
- you have constant, severe pain with no relief between contractions
- contractions are regular and coming every 5 minutes or more often (call for guidance), or any contraction lasts longer than 2 minutes
If something feels wrong, trust that feeling and call. In an emergency, call your local emergency number.
Track week 40 in Momi
Finish your pregnancy story in Momi. With Premium, you can turn your timeline into a PDF journey book. Momi follows your pregnancy week by week with your baby's size and development, and keeps your diary, bump photos, appointments, kick counts and contractions in one place.
Download Momi free on the App Store or Google Play. Free with ads; optional Premium.
Keep reading
← 39 weeks pregnant · All weeks
Sources
- ACOG: Changes During Pregnancy (infographic)
- ACOG: How to Tell When Labor Begins
- NHS: Signs that labour has begun
- NHS: Your baby's movements
Medical disclaimer: Momi and this website provide general information, not medical advice. Always talk to your doctor or midwife; in an emergency call your local emergency number.
FAQ
How big is a baby at 40 weeks pregnant?
On average, a baby at 40 weeks is about the size of a small pumpkin: about 51.2 cm (20.2 in), about 3.4 kg (7.6 lb). These are typical averages, and healthy babies vary.
How many months is 40 weeks pregnant?
40 weeks pregnant is in the ninth month of pregnancy and the third trimester. Months don't divide evenly into 40 weeks, so different sources may label the month slightly differently.
What should I do at 40 weeks pregnant?
Attend your 40-week check. Ask about next steps if you go past 41 weeks.
Related guides
Track this in Momi
Momi is a free pregnancy tracker app for iPhone and Android that follows pregnancy week by week, estimates the due date, and keeps a pregnancy journal, weight log, kick counter and contraction timer in one place.
