Baby is the size of a carrot
👶 Baby's development
The baby swallows about 400 ml of amniotic fluid per day. The immune system is developing.
💛 How mom feels
Movements become more distinct and regular. Night leg cramps may appear.
📖 Tip of the week
Movements are becoming stronger and more regular — soon you'll be able to count kicks. The baby responds to touches on your belly. Start keeping a kick count diary — 10 movements in 2 hours is normal from week 28.
🔬 Detailed baby development
- The fetus's movements are becoming stronger and more patterned, with periods of sleep and activity
- Bone marrow begins producing blood cells, taking over from the liver and spleen
- The small intestine begins absorbing nutrients from swallowed amniotic fluid
- The fetus's eyelids are fully formed but remain fused shut until about week 26
- Rapid weight gain begins as the fetus starts accumulating more fat
- The fetus is about 26.7 cm long and weighs approximately 360 grams, roughly the size of a carrot
🤱 What mom may feel
- Varicose veins may appear or worsen, especially in the legs
- Braxton Hicks contractions (practice contractions) may begin — they are painless and irregular
- Stretch marks may become more prominent as the belly grows
- Increased hunger and thirst as metabolic demands increase
- Spider veins (small red marks) may appear on the face, neck, or arms
🏥 Tests and check-ups
No specific scheduled tests for week 21. Continue regular prenatal visits every 4 weeks. If the anatomy scan identified any concerns, a follow-up ultrasound or referral to a maternal-fetal medicine specialist may be recommended.
💡 Tips for this week
- Avoid standing or sitting in one position for too long to help prevent varicose veins
- Wear compression stockings if varicose veins are bothersome
- Practice relaxation techniques (deep breathing, meditation, progressive muscle relaxation) to manage stress
- Continue increasing your protein intake to support the baby's rapid growth phase
❓ Frequently asked questions
What are Braxton Hicks contractions?
Braxton Hicks contractions are irregular, painless tightening of the uterus that can start as early as the second trimester. They are your uterus practicing for labor. Unlike true labor contractions, they are irregular, don't increase in intensity, and stop when you change position or rest.
Are varicose veins during pregnancy permanent?
Varicose veins often improve significantly after delivery, though they may not fully resolve. Staying active, elevating your legs, wearing compression stockings, and avoiding prolonged standing can help manage them during pregnancy.
How much protein do I need?
Pregnant women need about 71 grams of protein per day (compared to 46 grams for non-pregnant women). Good sources include lean meat, poultry, fish, eggs, dairy, beans, lentils, nuts, and tofu.
📝 Week 21 of pregnancy: what's happening
Your baby now measures around 26.7 cm from head to toe and weighs approximately 360 g — roughly the size of a large carrot. The bone marrow is now the primary site of red blood cell production, having taken over from the liver and spleen. Eyebrows and eyelids are fully formed, and the baby’s lips are more defined. The baby’s sleep–wake cycles are becoming more established, and you may notice patterns of activity at certain times of day.
You are likely feeling your baby’s movements regularly now, and these will continue to grow in strength as your pregnancy progresses. If you notice a significant reduction in your baby’s movements at any stage, contact your maternity unit immediately — do not wait until the next day. Pelvic girdle pain (PGP) — also known as symphysis pubis dysfunction (SPD) — may develop at this stage, causing discomfort in the pelvic area, hips, or thighs. Referral to a physiotherapist through your midwife can provide significant relief.
If your anomaly scan flagged any concerns, you may have follow-up appointments with a fetal medicine specialist or obstetrician at around this time. For most women, the next routine appointment will be at week 25 (for first-time mothers) or week 28 (for those who have given birth before), unless additional monitoring is required. Your midwife may measure your symphysis-fundal height (SFH) — the distance from your pubic bone to the top of your uterus — at each appointment from now on to track your baby’s growth.
Begin researching maternity leave options and your statutory entitlements in detail — in the UK, Statutory Maternity Leave is up to 52 weeks, and Statutory Maternity Pay (SMP) can be claimed if you have been employed for long enough and meet the earnings threshold. Consider speaking to your HR department or Citizens Advice for tailored guidance. This is also a good time to think about childcare options and, if relevant, to begin researching nurseries or childminders, as waiting lists in many areas are long. Planning ahead reduces stress later in pregnancy.
⚠️ When to see a doctor
- Vaginal bleeding of any amount
- Severe headache or vision changes
- Severe abdominal or lower back pain
- Swelling of face and hands (possible preeclampsia)
- Decreased or absent fetal movement after 20 weeks
- Blood pressure above 140/90
Sources
- WHO recommendations on antenatal care (2016)
- ACOG Practice Bulletins
- Williams Obstetrics, 26th Edition
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