Baby by Week
Week 21

Your week 21 guide

Brain-to-muscle connections are strengthening while bones and digestion mature.
Trimester

2

Month

5

Weeks left

19

Size at a glance

Comparison
Long banana
Length
18 cm
Weight
11 oz
Measurements are approximate. Healthy babies grow at different rates.

Baby development

Billions of neurons connect with muscles, supporting more active movement.
Cartilage continues hardening into bone and bone marrow starts making blood cells.
The fetus swallows amniotic fluid and passes waste to the large bowel.

Your body

Movement may range from gentle taps to stronger kicks.
Backache, leaking colostrum, and occasional Braxton Hicks tightenings can begin.
Hair and nails may grow faster.

This week's checklist

Review your anatomy-scan results and questions with your clinician.
Plan leave, support, or nursery needs at a pace that works for you.
Wear the lap belt below your belly and the shoulder belt between your breasts.

Call your care team

Call for bleeding, fluid leakage, painful regular contractions, fever, or severe abdominal pain.
Seek urgent help for chest pain, fainting, trouble breathing, or severe headache with vision changes or swelling.

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.