31 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 31 weeks pregnant, your baby is about the size of a coconut, about 41.1 cm (16.2 in) long. You're in the third trimester, in month 7, with 9 weeks to go until your due date. This week's milestone: major development largely done. Symptoms vary from person to person.
| Week 31 at a glance | |
|---|---|
| Trimester | Third |
| Month | 7 |
| Weeks to due date | 9 |
| Baby's size | About the size of a coconut |
| Length | About 41.1 cm (16.2 in) |
| Weight | About 1.5 kg (3.3 lb) |
| This week | Major development largely done |
Sizes are typical averages. Before about 20 weeks, length is measured crown to rump; after that, head to heel.
Your baby at 31 weeks
Your baby is about the size of a coconut and weighs about 1.5 kg (3.3 lb). ACOG says that at week 31 major development is finished, and the baby is gaining weight quickly.
Your body at 31 weeks pregnant
You may leak a little colostrum from your breasts, and Braxton Hicks may be more frequent.
Things to do this week
- Attend your 31-week appointment if it's your first baby (UK).
- Talk about your birth plan with your midwife or doctor.
- Know the signs of preterm labor.
When to call your doctor or midwife
Contact your care team straight away if:
- your baby is moving less than usual, has stopped moving, or the pattern has changed. The NHS says to call immediately, even in the middle of the night
- you have a severe headache, vision changes, pain below your ribs or sudden swelling (possible pre-eclampsia)
- you have intense itching, especially on the palms of your hands or soles of your feet
- you have contractions, your waters break or you bleed before 37 weeks
- you have a fever of 100.4°F (38°C) or higher
If something feels wrong, trust that feeling and call. In an emergency, call your local emergency number.
Track week 31 in Momi
Momi's contraction timer logs length and time apart if you need to tell your care team about tightenings. 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
← 30 weeks pregnant · All weeks · 32 weeks pregnant →
Sources
- ACOG: Changes During Pregnancy (infographic)
- NHS: Your baby's movements
- NHS: Antenatal care and appointments
- CDC: Urgent Maternal Warning Signs
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 31 weeks pregnant?
On average, a baby at 31 weeks is about the size of a coconut: about 41.1 cm (16.2 in), about 1.5 kg (3.3 lb). These are typical averages, and healthy babies vary.
How many months is 31 weeks pregnant?
31 weeks pregnant is in the seventh 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 31 weeks pregnant?
Attend your 31-week appointment if it's your first baby (UK). Talk about your birth plan with your midwife or doctor.
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.
