21 weeks pregnant: baby, body and what to expect

Trimester 2 of 3About 5 months19 weeks to go

Week 21 of pregnancy: baby is about the size of a carrot

Week 21 at a glance

At 21 weeks, the baby is often about 10.2 to 10.6 inches (26 to 27 cm) long and weighs around 12.7 ounces (360 g), roughly the size of a large carrot. Taste buds are developing, and the baby may begin to taste amniotic fluid.

21 weeks pregnant is about 5 months. You are in month 5 of pregnancy and the second trimester.

Your baby at 21 weeks

Your Baby's Taste Buds Are Developing

At 21 weeks, an important milestone is reached: taste buds are developing, and the baby may begin to taste amniotic fluid.

What is happening this week

The baby is often about 10.2 to 10.6 inches (26 to 27 cm) long and weighs around 12.7 ounces (360 g). Taste receptors and nerve pathways continue to mature, so the senses are developing actively at this stage.

The baby may swallow amniotic fluid and respond to its taste.
The brain, muscles, and senses continue to develop.
Movements often become more noticeable and coordinated.

On ultrasound, babies at this stage often show active movements, position changes, and practice breathing motions. If the baby seems less active during one scan, this is often related to position. Tell your provider if you have concerns about your baby's movement.

How this week may feel

In the second trimester, many people feel more energetic, although heartburn, shortness of breath with activity, or stretching in the ligaments can still happen. These changes are linked to uterine growth and hormones.

Call your OB-GYN or midwife right away if you have vaginal bleeding, fluid leaking from the vagina, severe pain, fever, regular painful contractions, or a sudden worsening in how you feel.

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Your body at 21 weeks

Why It Happens

At 21 weeks pregnant, many people notice a burning feeling in the chest or throat. This is called heartburn, or gastroesophageal reflux (GERD).

Why does heartburn happen?

Heartburn during pregnancy usually comes from a mix of hormonal and physical changes:

Hormones: Progesterone relaxes smooth muscle, including the valve (sphincter) between the stomach and esophagus. When this valve loosens, stomach acid can move up.
Physical pressure: Your growing uterus, which measures roughly 21 cm (about 8 inches) from the pubic bone at this stage, presses on your stomach.

Heartburn is a common and usually temporary part of pregnancy. It often improves after delivery.

How to feel better

Many providers suggest the following steps:

Eat smaller meals more often, rather than three large meals.
Try not to lie down right after eating. Staying upright for a while can help acid stay down.
Raise the head of your bed or use extra pillows so your head and chest are slightly elevated when you sleep.
Notice which foods trigger your symptoms, such as spicy, fried, or very fatty foods, and limit them if they make you feel worse.
Ask your provider before taking any antacid or heartburn medicine. Some over-the-counter options are often considered safe in pregnancy, but your provider can help you choose one.

Call your healthcare provider if heartburn comes with severe pain, repeated vomiting, trouble keeping food or fluids down, or weight loss. Call 911 or go to the nearest emergency room if you have chest pain, shortness of breath, or pain spreading to your arm, jaw, or back, since these symptoms need urgent care.

Common symptoms at 21 weeks

Heartburn

A burning feeling in the chest or throat is common as the uterus grows and pregnancy hormones relax the valve between the stomach and esophagus. Smaller meals and staying upright for a while after eating often help.

Round ligament pain

Sharp or pulling pain in the lower belly or side can happen as the muscles that support the uterus stretch. Changing position slowly and resting can ease it for many people.

Constipation

Slower digestion and iron in prenatal vitamins can make bowel movements harder. Drinking more water, eating fiber from fruits, vegetables, and whole grains, and moving your body daily can help.

Swelling in the feet and ankles

Extra fluid in the body can cause puffiness, especially by the end of the day. Raising your feet and avoiding long periods of standing may bring some relief.

Stuffy nose

Increased blood flow can cause the nasal passages to swell, so congestion or nosebleeds may happen. A saline spray or a humidifier may help, and your care team can suggest other options.

Leg cramps

Muscle cramps, often at night, are common in pregnancy. Stretching your calves before bed and staying hydrated may help some people feel more comfortable.

Your week 21 checklist

Eat smaller meals and try not to lie down within about two to three hours of eating. Keep a water bottle nearby and sip through the day. Add one more fiber-rich food to your meals, such as oats, beans, or pears. Write down any new symptoms to share at your next prenatal visit. Ask your care team which heartburn medicines and pain relievers are safe to use in pregnancy. Book your anatomy ultrasound if it is not already scheduled.

Tests and appointments

Anatomy ultrasound. This detailed ultrasound, usually done between about 18 and 22 weeks, checks the baby's growth, organs, and body structures, and it often shows the baby's sex if you wish to know.

For your partner: A partner can help by taking over some cooking, especially smaller, lighter meals that ease heartburn, and by handling errands that involve a lot of standing or lifting. Offering a calf massage at night or going along to an ultrasound can also make the week feel more shared.

Questions about week 21

How many months is 21 weeks pregnant?

21 weeks pregnant is about 5 months. You are in month 5 of pregnancy and the second trimester.

What trimester is 21 weeks?

Week 21 is in the second trimester. The first trimester runs through week 13, the second from week 14 to 27 and the third from week 28 until birth.

What is happening with the baby at 21 weeks?

At 21 weeks, the baby is often about 10.2 to 10.6 inches (26 to 27 cm) long and weighs around 12.7 ounces (360 g), roughly the size of a large carrot. Taste buds are developing, and the baby may begin to taste amniotic fluid.

Is it normal to feel the baby move around now?

Many people start to feel movement between about 18 and 25 weeks, and first-time parents often notice it later. Flutters, bubbles, or small taps are common. If you are unsure what you feel or movement seems to slow down, contact your care team.

Can the baby really taste what I eat?

Taste buds are forming now, and the baby may taste flavors in the amniotic fluid. Some researchers think early taste exposure may play a role in food preferences later, but more study is needed.

Why does my nose bleed more during pregnancy?

Higher blood volume and hormone changes make the lining of the nose more sensitive and prone to swelling. Gentle nose blowing and a humidifier may help, and you should mention frequent or heavy nosebleeds to your care team.

Safe or not?

LimitCan I eat brie while pregnant?AvoidCan I eat smoked salmon while pregnant?LimitCan you drink energy drinks while pregnant?LimitCan you eat tuna while pregnant?

Guides for this stage

Mental healthFeeling Less Attractive in Pregnancy: Learning to Accept a Changing Body Medical careCervical length check in pregnancy: what the test shows HealthManaging chronic conditions during pregnancy FeedingColostrum Leaking in the Second Trimester: What's Normal and What to Do

Coming up next weekWeek 22: Touch Is Developing, and the Baby May Touch Its Face and Umbilical CordRead week 22 →

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Learn more

NIH: Pregnancy (NICHD)
CDC: Pregnancy

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General information only; it does not replace advice from your doctor or midwife.