Baby by Week
Week 31

Your week 31 guide

Rapid brain, lung, and fat development continues as the fetus practices coordinated movement.
Trimester

3

Month

8

Weeks left

9

Size at a glance

Comparison
Coconut
Length
46 cm
Weight
> 3 lb
Measurements are approximate. Healthy babies grow at different rates.

Baby development

The brain forms more connections and can process information from the senses.
The lungs keep maturing, although they are not yet fully ready for independent breathing.
Growth may make movement feel more like rolling and stretching than large flips.

Your body

Bladder pressure, back pain, clumsiness, headaches, and poor sleep can increase.
Shortness of breath can happen as the uterus pushes upward.
Pregnancy-related forgetfulness can make notes and reminders useful.

This week's checklist

Pack or outline a hospital bag based on your birth location.
Learn the signs of preterm labor and who to call after hours.
Complete essential nursery or sleep-space safety tasks before decorative extras.

Call your care team

Call maternity care immediately for reduced movement, bleeding, fluid leakage, or regular painful contractions.
Seek urgent help for severe headache with vision changes, chest pain, fainting, severe abdominal pain, or shortness of breath that is sudden or severe.

Medical information, not medical advice

Every pregnancy is different. Use this guide for general education and follow the advice of your own maternity care team. Do not delay urgent care because of something you read here.