21 Weeks Pregnant: Baby Can Hear You Clearly Now

At 21 weeks pregnant, your baby is about the size of a large carrot (approximately 26-27 cm or 10.2-10.6 inches head to toe). Your baby can hear you clearly now and may respond to sounds, music, and your voice. Movements are strong and becoming more coordinated. You’re past the halfway point!¹

What’s Happening at 21 Weeks Pregnant?

Week 21 takes you past the halfway point of pregnancy and deeper into the comfortable second trimester. You’re likely feeling great—energetic, comfortable, and excited about your growing baby. Your bump is obvious, movements are regular and strong, and pregnancy feels very real.

Your baby is growing rapidly and practicing all the skills needed for life after birth. Hearing is well-developed, and your baby may respond to sounds—startling at loud noises or becoming active when hearing familiar voices or music.²

This is an excellent time to enjoy your pregnancy, prepare for your baby’s arrival, and make memories before your baby arrives.

How Big is My Baby at 21 Weeks?

Your baby at 21 weeks is about the size of a large carrot or pomegranate, measuring approximately 26-27 centimeters (10.2-10.6 inches) from head to toe and weighing about 360-380 grams (12.7-13.4 ounces).³

Your baby is gaining weight steadily as fat continues accumulating, helping fill out the skin and preparing for temperature regulation after birth.

Baby Development at Week 21

Significant sensory and physical refinements characterize this week:

Advanced hearing: Your baby’s hearing is well-developed, and they can hear a wide range of sounds clearly:

• Your voice and heartbeat
• Your partner’s voice
• Music
• Household noises
• Loud external sounds⁴

Your baby may respond to these sounds by moving, kicking, or changing activity levels. Some research suggests babies can recognize voices they hear frequently in the womb after birth.

Taste preferences forming: Your baby is swallowing amniotic fluid constantly and can taste what you eat. This exposure to different flavors may influence food preferences after birth.

Digestive system maturation: Your baby’s digestive system is becoming more sophisticated, processing the amniotic fluid they swallow and producing meconium (first stool).

Movement coordination: Movements are becoming increasingly coordinated and purposeful:

• Strong kicks and punches
• Somersaults and barrel rolls
• Stretching and yawning
• Grasping hands and feet
• Sucking thumb
• Playing with umbilical cord⁵

Sleep patterns: Your baby has established sleep-wake cycles, sleeping about 12-14 hours per day in short bursts (20-40 minutes at a time).

Bone marrow function: Bone marrow has taken over red and white blood cell production from the liver and spleen, an important step toward independent immune function.

Skin development: Skin is becoming less transparent as fat accumulates beneath it. Vernix (protective coating) and lanugo (fine hair) cover the body.

Eyebrow and eyelash growth: Eyebrows and eyelashes are well-developed and visible.

Rapid brain growth: The brain is growing rapidly, with billions of neurons forming complex connections. This growth will continue throughout pregnancy and well into childhood.

Lung development: Lungs are developing air sacs (alveoli) and producing surfactant, a substance that will help lungs inflate after birth.

Common Symptoms at 21 Weeks Pregnant

Week 21 typically brings continued second-trimester comfort:⁶

Strong, regular fetal movements: Most people feel movements multiple times daily now. Movements are graduated from flutters to strong kicks, punches, and rolls.

Growing bump: Your bump is obvious and growing steadily.

Good energy: Most people maintain good energy levels during this phase.

Increased appetite: Your baby is growing rapidly and needs additional nutrition.

Shortness of breath: Your expanding uterus pushes up on your diaphragm, slightly reducing lung capacity.

Lower back pain: Common as your belly grows and your posture changes.

Heartburn: Ongoing as your uterus pushes on your stomach.

Leg cramps: May occur, especially at night.

Swollen feet and ankles: Mild swelling is normal, especially at the end of the day.

Increased vaginal discharge: Normal and protective throughout pregnancy.

Braxton Hicks contractions: Painless “practice contractions” may occur occasionally.

Skin changes: Linea nigra, darker areolas, possible stretch marks developing.

Varicose veins: Some people develop visible, swollen veins in legs or vulva due to increased blood volume and pressure.

Weight gain: Steady weight gain of about 1 pound per week continues.

When to Call Your Doctor

Contact your healthcare provider if you experience:

• Heavy bleeding
• Severe abdominal pain
• Regular, painful contractions
• Fever above 100.4°F (38°C)
• Sudden severe swelling, especially of hands and face
• Severe persistent headache with vision changes
• Significantly decreased fetal movement

Tips for Week 21

Talk and sing to your baby: Your baby can hear you clearly now. Talking, reading, or singing to your baby may help them recognize your voice after birth.

Play music: Many babies respond to music in the womb. Notice if certain music calms or activates your baby.

Continue balanced nutrition: Focus on nutrient-dense foods including lean proteins, fruits, vegetables, whole grains, and healthy fats.

Stay active: Continue regular, moderate exercise. Swimming is particularly beneficial as it takes pressure off your joints and back.

Address shortness of breath: Practice good posture, avoid overexertion, sleep propped up slightly, and take breaks when needed.

Manage swelling: Elevate feet when resting, avoid prolonged standing, stay hydrated, reduce sodium, and wear compression socks.

Prevent or minimize varicose veins: Avoid standing for long periods, elevate legs when resting, wear compression stockings, exercise regularly, and avoid crossing your legs.

Address back pain: Practice good posture, wear supportive shoes, sleep with pillow support, and consider prenatal massage or chiropractic care.

Stay hydrated: Aim for 8-10 glasses of water daily.

Sleep on your left side: This position optimizes blood flow to your baby.

Start infant CPR research: Consider registering for infant CPR and first aid classes.

Plan for maternity leave: If you work, start planning your maternity leave details and discussing them with your employer.

Tracking Your Pregnancy with Nooko

At 21 weeks pregnant, your baby can hear you clearly and movements are strong and regular. Tracking these interactions helps you bond with your baby and appreciate their development.

With Nooko, you can log when movements occur and note patterns—does baby respond to certain sounds or music? Become active after meals? Have quiet times? Track these patterns to learn your baby’s personality even before birth.

Document conversations you have with your baby, songs you sing, or books you read. Access detailed information about your baby’s hearing development and what they can perceive. Track symptoms, nutrition, and exercise. Take weekly bump photos. Download Nooko to stay connected to your baby and document your journey.

Download Nooko on the App Store | Get Nooko on Google Play

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References

Footnotes

1. American College of Obstetricians and Gynecologists. (2025). “How Your Fetus Grows During Pregnancy.” https://www.acog.org/womens-health/faqs/how-your-fetus-grows-during-pregnancy ↩

2. Mayo Clinic. (2024). “Fetal development: The 2nd trimester.” https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20046151 ↩

3. BabyCenter. (2025). “21 weeks pregnant: Symptoms, baby development, and more.” ↩

4. Cleveland Clinic. (2025). “Fetal Development: Week-by-Week Stages of Pregnancy.” https://my.clevelandclinic.org/health/articles/7247-fetal-development-stages-of-growth ↩

5. Parents. (2024). “Second Trimester Fetal Development: Week by Week.” https://www.parents.com/pregnancy/stages/fetal-development/second-trimester-images-of-your-developing-baby/ ↩

6. Mayo Clinic. “Symptoms of pregnancy: What happens first.” https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/symptoms-of-pregnancy/art-20043853 ↩