Second trimester
21 weeks pregnant
Your baby is about the size of a carrot
By Clever Mum Parenting · Parenting guides
How big is the baby at 21 weeks pregnant?
At 21 weeks pregnant, your baby is about the size of a carrot, roughly 26.7cm and around 360g. The baby's movements are getting stronger and more coordinated — you may notice patterns to when they're active. Their digestive system is practising for milk. These are typical averages — your midwife's measurements are the ones that matter for your pregnancy.
What might you feel at 21 weeks?
Most people at 21 weeks notice some mix of the symptoms below — and plenty notice none of them. Appetite is often strong now. Some experience swollen feet, indigestion or shortness of breath as the uterus rises. Stretch marks may appear on the bump, hips or breasts. None of this is a diagnosis; contact your midwife if something worries you.
Common symptoms this week
- Stronger, patterned movements
- Swollen feet by evening
- Indigestion beginning
- Possible stretch marks
Symptom lists are typical, never exhaustive — and having none of them is normal too.
What should you do at 21 weeks pregnant?
The useful job this week is practical, not medical. Start noting your baby's movement patterns. From now, getting to know what's normal for your baby matters — report any reduction to your maternity unit straight away. Pair it with the NHS week-by-week guide if you want a second description of the same stage.
Week 21 checklist
- Start tuning into your baby's movement pattern — from now, knowing what's normal for your baby matters
- Save your maternity unit's triage number in your phone
What else is useful at 21 weeks?
Use the week page for size and symptoms; use the guides below for the decisions that actually sit in this window — pay, packing, car seats, labour signs.
21 weeks pregnant: common questions
How many kicks should I feel a day?
There's no set number — the NHS moved away from kick counts. What matters is your baby's own pattern: once you know their normal, any slowdown or change is the signal. Report reduced movements to your maternity unit immediately, day or night, and never wait until morning.
How big is my baby at 21 weeks pregnant?
At 21 weeks, your baby is approximately the size of a carrot, about 26.7cm and around 360g. These are approximate averages — every baby grows at its own pace.
What's happening at 21 weeks pregnant?
The baby's movements are getting stronger and more coordinated — you may notice patterns to when they're active. Their digestive system is practising for milk. For you: appetite is often strong now. some experience swollen feet, indigestion or shortness of breath as the uterus rises. stretch marks may appear on the bump, hips or breasts.
Which trimester is 21 weeks?
21 weeks pregnant is in the second trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night. Reviewed August 2026.