Week 21 of pregnancy
Week 21 sits in the middle stretch of pregnancy, the second trimester.
What's developing
The baby is now heavier than the placenta and can hear noises and voices outside the womb. [1]
What you might notice
You may feel unsteady as your center of gravity shifts and your joints loosen. If you fall, tell your midwife as soon as you can. [1]
Everyone's pregnancy is different. If something worries you, call your midwife or doctor.
A tip for this week
The baby may be wide awake just when you want to sleep. Nap when you can to make up for it. [1]
Questions you could bring to your next appointment
- When is my mid-pregnancy scan?
- Will I be offered a glucose test?
- Is there anything I should change about exercise or work?
Questions
When will I feel the baby move?
The NHS says between 16 and 24 weeks. In a first pregnancy you might not feel movements until after 20 weeks.
What if I haven't felt the baby move by 24 weeks?
Tell your midwife or doctor. They'll check your baby's heartbeat and movements.
Is my baby exactly this size?
Probably not exactly. The length is the average the NHS gives for this week, and the weight is the middle value (50th percentile) of the WHO fetal growth charts. Your scan results are the ones that count.
Sources
- NHS: 21 weeks pregnant guide Checked October 30, 2026
- NHS: Your baby's movements Checked October 30, 2026
- WHO: The World Health Organization fetal growth charts (Kiserud et al., PLoS Medicine 2017), table 11: estimated fetal weight Checked October 30, 2026
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