39 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 39 weeks pregnant, your baby is about the size of a small watermelon, about 50.7 cm (20 in) long. You're in the third trimester, in month 9, with 1 week to go until your due date. This week's milestone: full term. Symptoms vary from person to person.
| Week 39 at a glance | |
|---|---|
| Trimester | Third |
| Month | 9 |
| Weeks to due date | 1 |
| Baby's size | About the size of a small watermelon |
| Length | About 50.7 cm (20 in) |
| Weight | About 3.3 kg (7.3 lb) |
| This week | Full term |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 39 weeks
Your baby is about the size of a small watermelon and weighs about 3.3 kg (7.3 lb). At 39 weeks your baby is full term.
Your body at 39 weeks pregnant
Labor could start any day, but it's normal to still be waiting. ACOG says most people give birth between 38 and 41 weeks.
Things to do this week
- Time contractions from the start of one to the start of the next.
- Call your provider if you think you're in labor or aren't sure.
- Keep track of your baby's movements, which should continue right up to labor.
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 39 in Momi
Keep Momi's contraction timer handy on your home screen. 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.
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Keep reading
← 38 weeks pregnant · All weeks · 40 weeks pregnant →
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 39 weeks pregnant?
On average, a baby at 39 weeks is about the size of a small watermelon: about 50.7 cm (20 in), about 3.3 kg (7.3 lb). These are typical averages, and healthy babies vary.
How many months is 39 weeks pregnant?
39 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 39 weeks pregnant?
Time contractions from the start of one to the start of the next. Call your provider if you think you're in labor or aren't sure.
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.
