What to know at 21 weeks pregnant: Symptoms & baby size

An illustration of a uterus and a fetus the size of a carrot representing 21 weeks pregnant.
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Created with Natasha Lowe Osho, MD, Obstetrician-Gynecologist, USA

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In a nutshell

At 21 weeks pregnant, your baby is actively moving, practicing reflexes, and growing stronger. About the size of a carrot, your baby’s movements may become more pronounced, and their senses are sharpening. You may notice a rounder belly, improved energy levels, and occasional symptoms like backaches or leg cramps.

Congratulations on reaching 21 weeks pregnant! This week, your baby is growing rapidly and becoming more active in the womb. For you, week 21 is an exciting time as your belly continues to grow, and you may feel more connected with your little one through their kicks and stretches. Let’s dive into what’s happening this week, from your baby’s development to expert advice on managing symptoms and staying healthy.

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21 weeks pregnant symptoms

As you progress through week 21, here’s what you may experience:

  • Increased appetite: Your growing baby and increased blood volume may leave you feeling hungrier than before.
  • Backaches: With your uterus expanding, additional pressure on your lower back can cause mild discomfort.
  • Leg cramps: Changes in circulation and increased weight can lead to nighttime cramps.
  • Baby movements: Your baby’s kicks and rolls may become more distinct, especially during quiet times.
  • Stretch marks: As your belly and breasts grow, stretch marks may appear due to skin stretching.

👉Find out more: Halfway there: Insights on being 20 weeks pregnant and fetal development

Your body at 21 weeks pregnant

At week 21, your uterus is continuing to expand, moving further above your belly button. This shift may cause occasional back discomfort or strain on your abdominal muscles. You might also notice changes in your skin, such as a darkening linea nigra or increased stretch marks. Staying hydrated, moisturizing your skin, and maintaining a healthy diet can help manage these changes.

21-week pregnant belly

Your belly is becoming more prominent as your baby grows, and many moms-to-be feel a sense of pride in their bump. Maternity clothes are often the most comfortable option at this stage, providing flexibility and support as your body changes.

Baby development at 21 weeks pregnancy

At 21 weeks, your baby is practicing essential reflexes, such as swallowing and sucking. They’re also developing their sense of touch and may respond to external stimuli, like your voice or gentle pokes on your belly. The baby’s digestive system is maturing, and they’re even swallowing small amounts of amniotic fluid to prepare for feeding after birth.

21-week baby size

The 21-week fetus size is around 10.5 inches long from head to heel and weighs about 12.7 ounces—roughly the size of a carrot. As their muscles and bones strengthen, your baby’s movements will feel more distinct.

21-week ultrasound

A 21-week ultrasound may provide a detailed view of your baby’s organs, limbs, and movements. During this scan, you can check on their growth and development. If you’ve had your anatomy scan (typically done between weeks 18 and 22), you may have learned your baby’s gender, though this is optional. This ultrasound also ensures your baby’s organs, brain, and heart are developing normally.

Tests to expect at 21 weeks pregnant

At week 21, regular prenatal care is essential to ensure you and your baby remain healthy. Here’s a breakdown of tests and their purposes:

  1. Routine Checkups:
    • Blood pressure check: Monitoring for preeclampsia or hypertension.
    • Urine test: Screening for protein (a sign of preeclampsia) and glucose (to monitor gestational diabetes).
  2. Glucose tolerance test (GTT): Typically scheduled between weeks 24-28 but might be discussed now. This test evaluates how your body processes sugar and identifies gestational diabetes risk.
  3. Anatomy scan follow-up: If not done earlier, a detailed ultrasound ensures proper organ development and checks the placenta’s position.
  4. Fundal height measurement: This measures the growth of your uterus and helps assess your baby’s development.

👉Find out more: 

22 Weeks pregnant: Fetal development, body changes, and key insights

What to expect at 23 weeks pregnant: Baby size & movements
Expert advice: Discuss any concerns about your baby’s growth, movements, or your symptoms during these checkups. Regular prenatal visits are an opportunity to stay informed about your health and your baby’s progress.

Health tips and self-care at 21 weeks pregnant

  • Stay active: Gentle exercises like walking, swimming, or prenatal yoga can help with circulation and reduce back pain.
  • Hydrate and moisturize: Drink plenty of water to support skin elasticity and minimize stretch marks.
  • Listen to your body: Rest when needed, and don’t hesitate to take breaks to manage fatigue.
  • Engage with your baby: Talk or sing to your baby—they can now hear your voice, which strengthens your bond.
Curious about the stages of pregnancy development?

Femia decodes your body’s signals and helps you track progress effortlessly

Try Femia now

Questions from the Femia community

  • What is a nesting syndrome?

    Nesting syndrome is the instinct to prepare your home for your baby’s arrival, often involving organizing, cleaning, or decorating. It’s completely normal and often peaks in the third trimester.

  • Should I be vaccinated during pregnancy?

    Yes, vaccines like the flu shot, RSV vaccine, and Tdap are recommended during pregnancy to protect you and your baby from serious illnesses. Discuss vaccination timing with your healthcare provider.

  • Is my weight gain normal?

    The normal weight gain in the second trimester is 0.5 to 1 lb per week based on your pre-pregnancy weight. For a basic check, you can also use a pregnancy weight gain calculator. Your healthcare provider can guide you based on your pre-pregnancy weight and overall health.

  • How can I reduce leg cramps?

    Stretching before bed, staying hydrated, and eating magnesium-rich foods like nuts and leafy greens can help alleviate leg cramps.

The bottom line

At 21 weeks pregnant, your baby is developing rapidly, practicing movements, and responding to sounds. Your belly is more prominent, and symptoms like back pain or leg cramps may arise. Focus on hydration, balanced nutrition, and staying active to support your health and enjoy this exciting stage.

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