How big is the baby in week 40 of pregnancy?

In week 40, your baby is roughly 51.2 cm long and weighs about 3.46 kg — about the size of watermelon.

40 of 40 weeks

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Third trimester

Week 40

It's your due week — any day now.

Baby size this week

As lovely as a watermelon

Measurements are averages — every baby grows at their own pace.

Length 51.2 cm 20.2 in

Weight 3.46 kg 7 lb 10 oz

Your baby this week

Your baby is full term — congratulations
The average newborn is about 51 cm and 3.4 kg
Your baby's skull plates overlap during birth — that's normal
Only about 4% of babies arrive exactly on their due date

Your body this week

Strong Braxton Hicks

Pelvic pressure

Nesting instinct

Better breathing

A little list for week 40

This week's to-do

Use the contraction timer and 5-1-1 guide Stay in touch with your midwife Gentle walks may encourage labor Every day past 40 weeks, monitoring increases A pre-packed hospital bag for the big dayHelpful pick

How we measure week 40

Pregnancy weeks are counted from the first day of your last menstrual period, following standard ACOG and NHS guidance. Sizes are crown-rump length in early weeks and head-to-heel from around week 20. Your care team may adjust dates after an ultrasound.

Recalculate your due date

BumpCount offers general information and does not replace advice from your doctor or midwife.

Week 40

As lovely as a watermelon

Your baby this week

Your body this week

This week's to-do

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