Pregnancy Guide

21 Weeks Pregnant

Your baby is the size of a Ear of Corn. Discover exactly what is happening to your body and your baby this week.

New pregnancy guide: Learn how weeks are counted, what each trimester means, and how to interpret your calculator results for better preparation and planning. Read the full guide
Medical & Editorial Review
Content reviewed against NHS and ACOG clinical guidelines.
Last reviewed: August 2026. This information is for educational purposes only and does not substitute professional medical advice. Always consult your healthcare provider.

21 Weeks Pregnant Fetal Development

Baby Development: Movements form a recognisable pattern — you'll start to learn your baby's active times. Rapid eye movements occur during sleep. Fingernails are fully formed.

Pregnancy Symptoms: Heartburn and indigestion may intensify as the uterus pushes against your stomach. Sleeping with your head elevated helps.

Weekly Tip: Shop for a maternity bra — your cup size will change significantly during pregnancy and nursing.

At 21 weeks pregnant, your baby is approximately the size of a Ear of Corn.

Week 21 in detail

Swallows, REM sleep, and a pattern of kicks

Baby this week

The digestive tract is practising: the baby swallows amniotic fluid. Movements often settle into a daily pattern (frequently when you lie down). Eyebrows and lids are formed. Rapid eye movements happen in sleep.

  • Swallowing fluid is practice, not hunger
  • Fingernails have reached the fingertips on many fetuses
  • An anterior placenta can still muffle kicks — patterns matter more than force

Your body this week

The uterus is around the navel. Heartburn is the classic week-21 complaint: hormones loosen the stomach valve and the bump shoves upward. Smaller meals beat a heroic dinner. Sleeping with the head raised is dull and effective.

  • Spicy food is a personal experiment, not a medical ban
  • Iron needs rise; constipation from iron tablets is common — ask about forms
  • A maternity bra now is cheaper than pretending sports bras still fit

Get ready

Eat smaller meals if reflux is running the night. The checklist above is food timing, bras, and iron. If heartburn comes with shortness of breath that is new and severe, that is chest, not chilli — get urgent care.

A general guide, not medical advice. Scan timing and symptoms vary — ask your clinician.

Baby Growth Curve

This chart visualizes the average length of the baby from week 1 to 40. Values are based on standard clinical averages.

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