21 Weeks Pregnant: Baby Development, Symptoms & Signs

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10.5 in, 11 - 12.5 oz26.7 cm, 0.31 - 0.35 kg

19Weeks to go!

by Catherine Donaldson-Evans reviewed mark

Medically Reviewed by Jennifer Wu, M.D., F.A.C.O.G.

All What to Expect content that addresses health or safety is medically reviewed by a team of vetted health professionals. Our Medical Review Board includes OB/GYNs, pediatricians, infectious disease specialists, doulas, lactation counselors, endocrinologists, fertility specialists and more.

We believe you should always know the source of the information you're reading. Learn more about our editorial and medical review policies. | July 29, 2025 Latest update: See more EXPLORE PREGNANCY WEEK 21

Baby development
Body changes
Common symptoms
Tips for you
Recommended products
Birth month group discussions

At 21 weeks pregnant, your baby has more control over limb movements, which explains why you might be feeling more kicking and stretching going on in there.

From the outside, your little one may be leaving his mark in the form of stretch marks — pink, red, purple, reddish-brown, or dark brown streaks that can appear as your belly expands.

Your Baby at Week 21

At a Glance

He's got the movesYour baby's arms and legs are in proportion this week and his movements are now much more coordinated. Also, notice a jump in baby's length this week? Up until now, we've been measuring from crown to rump, but now we start to measure from crown to heel, which explains why he suddenly "grew" so much.

More blood cellsYour baby-to-be's liver and spleen have been working hard producing blood cells, but now the bone marrow is developed enough to help too.

Baby's drinkingWhile the placenta is still #1 when it comes to nourishment, now your baby takes in small amounts of amniotic fluid, too.

21 weeks pregnant is how many months?

If you're 21 weeks pregnant, you're in month 5 of your pregnancy. Only 4 months left to go! Still have questions? Here's some more information on how weeks, months, and trimesters are broken down in pregnancy.

How big is my baby at 21 weeks?

How big is your baby? Switching from crown-to-rump to crown-to-heel length, he's 10½ inches long and weighs 11 to 12½ ounces, about the size of a large banana.

Your developing baby still has a great deal of room in your womb — though like anyone who lives in one space for a long time, this tenant will soon begin to feel cramped.

Baby's moving and sleeping

Until those uterine walls start closing in, however, there's plenty of space for twisting, turning, and even doing the occasional somersault — so that's what you were feeling last night!

With all that belly dancing going on, it's hard to believe your baby is getting any shut-eye at all. But believe it or not, your fetus sleeps as much as a newborn. Now if only you could get some sleep yourself!

Baby's taste buds develop

Speaking of milestones, whatever you eat this week, there's a good chance your baby will taste it too. That's because when you're 21 weeks pregnant, your baby swallows a bit of amniotic fluid each day — not only for nutrition and hydration, but also to practice swallowing and digesting, skills he'll need as soon as he arrives in your arms.

And keep this in mind: The taste of the amniotic fluid differs from day to day depending on what you've eaten — spicy enchilada one day, sweet banana the next. That smorgasbord of flavors won't be lost on your baby since your little one has very developed taste buds already.

In fact, researchers have found that babies who were exposed to certain tastes in utero via the amniotic fluid were more eager to eat foods with those same tastes after birth. Want your cutie to eat his broccoli later? Eat yours now!

Baby's getting coordinated

Your little action figure is able to choreograph Matrix-like moves at 21 weeks pregnant. Arms and legs are finally in proportion, neurons are now connected between the brain and muscles, and cartilage throughout the body is turning to bone.

All these upgrades combine to give your baby more control over limb movements, which explains all that kicking, stretching, and body surfing you may have started feeling.

Your Body at Week 21

Stretch marks

At 21 weeks pregnant, your baby might be starting to leave his mark — in the form of stretch marks, that is — all over your stomach, butt, thighs, hips, and breasts.

These pink, red, purple, reddish-brown, or dark brown streaks appear as your body expands and your tummy and breasts just keep on growing. The supporting tissue under your skin gets torn as the skin stretches.

Estimates vary, but at least 1 in 2 women get stretch marks, though you're a likely candidate if your mom had them during pregnancy.

Rapid weight gain can also predispose you to getting stretch marks — another good reason to try to add on weight more slowly and steadily, at an average of about a pound a week.

Depending on your complexion and the genes you inherited, these lines first show up as red, pink, or brown streaks, and with time, will eventually fade.

There's no proven way to prevent stretch marks from zigzagging their way across your body (though there's no harm in applying moisturizers like cocoa butter; if nothing else, it will prevent the dryness and itching associated with pregnancy-stretched skin). After delivery, they usually fade to a less noticeable shade.

Relieving anxiety

Now that you're likely starting to look pregnant and those kicks can no longer be mistaken for gas, the reality of pregnancy may be sinking in even more than before.

And with it, you may find yourself having a few ambivalent or anxious feelings you're even ambivalent about admitting: Me, a mom? There must be some mistake!

Don't worry — and hang in there. At some point in pregnancy, just about every expectant parent begins to feel anxiety and fear — almost as if you're on a runaway train and worried about the unknowns coming around the bend.

Not only is it completely normal to feel anxious, it's healthy to acknowledge it. Talk your feelings over with your friends who've had babies — they’ll reassure you that they had the same kind of thoughts. And try to discuss your fears with your partner, if you have one, who is probably going through some of the same things as you are.

Learn more about anxiety during and after pregnancy.

Pregnancy Symptoms Week 21

Bloating and gas The increasing pressure your uterus is placing on your rectum can mean that you’re having a hard time containing yourself (your gas, that is). Drink plenty of water and eat fiber-rich foods to avoid becoming constipated, which can make gassiness worse. Read More

Backaches Not only is your center of gravity shifting and putting extra strain on your back, but the hormone relaxin is also causing your ligaments and joints to stretch and loosen, which means additional achiness in your back. If you can, splurge for a prenatal massage from a trained professional and spring for a pair of supportive shoes. Read More

Increased appetite Are you always in the mood … to eat? Carry healthy snacks such as nuts, raisins, trail mix, or granola bars so you’ll have nutritious fuel to keep you and your baby-to-be nourished, even when you’re on the go. Read More

Bleeding gums If your inflamed, bleeding gums are turning your toothbrush pink, avoid eating sticky candies, especially when you can’t brush afterward. The sweet stuff increases bacteria in your mouth and further irritates your gums. Read More

Fast-growing nails Have you noticed that your hair and nails are growing at record speed? Pregnancy hormones are partly the cause — as is the increased circulation in your body — bringing extra nutrients to your hair and nails ... as well as to your baby! Read More

Fetal movement By now, you may be able to feel your baby twisting, turning, and kicking in the womb — though many new expectant moms mistake the feeling for gas. Enjoy these first gentle love taps — soon enough your growing baby’s kicks will get stronger. Read MoreTrack your symptoms with the My Journal tool in our free app

Tips for You This Week

Put your feet up

Finding it harder to tie your shoes than usual? Swollen feet and ankles may be to blame. So go ahead, put your feet up!

Because your body has about 50% more blood and fluid than it did pre-baby, your extremities are more prone to swelling. So be sure to clock in a few sit-and-kick-back sessions throughout the day.Write some reminders

It's not a lack of sleep that's causing you to forget where you put your keys (though that certainly doesn't help). Brain fog is a common pregnancy symptom, and causes forgetfulness and trouble concentrating.

Since so-called “pregnancy brain” could well be here to stay for the remainder of your pregnancy, now's the time to start making to-do lists, jotting down notes for yourself, and outsourcing some of your regular tasks to your partner, friends, and family.Take a walk

Is your plumbing clogged? Then start walking for exercise. Both during pregnancy and in those early postpartum weeks, physical activity like a brisk walk is one of the best ways to stimulate your bowels and fight constipation.

Just a half-hour walk a day (or 30 minutes spread out in smaller increments) can do the trick, especially if you drink plenty of water and favor fiber-rich foods.

Just remember to take some trail mix when you hit the trail. And even if you’re not doing it to relieve constipation or other pregnancy symptoms, walking is a great way to get the exercise you need when you’re pregnant.Break the big sibling news

You’ve already made the announcement to your family and friends, to much fanfare — but telling your toddler that you’re expecting is likely to be met with … crickets.

It’s not surprising: Your toddler’s whole world will be changing, and that can be upsetting (not to mention a little scary). To help ease the transition, read your child books about pregnancy like Before You Were Born: The Inside Story, or pull up some old pictures of when you were pregnant with her.

Once you can feel the baby move, put her hand on your belly so she can feel the tiny flutters, or ask her to weigh in on potential baby names.Unstuff your nose

Seasonal allergies may not be to blame for all that nasal congestion you've been experiencing. Alas, starting in the second trimester, a stuffy nose is a common pregnancy symptom — one that tends to stick around until delivery. It can lead to trouble sleeping and even a new habit of snoring.

To clear your nasal passages, use your thumb to close one nostril, while gently blowing out the other. Then repeat on the other side.

If you're really stuffed up, ask your doctor if there's a safe OTC decongestant or antihistamine you can use. Nasal strips can also help.Rethink hair removal

Shaving used to be a cinch — but now, you might have trouble seeing below your belly. While a shower can soften your hair and skin, making it easier to remove, always shave after you've finished, since a slip-up could be serious.

If your skin isn't too sensitive, you might want to try waxing and sugaring (ask your doctor if it's okay first), which is a long-term solution to unwanted hair.

As for bleaches, lasers, and hair removal creams, the jury is still out on whether they're safe to use during pregnancy, so consider shelving them until after you give birth.Go for a swim

Want a reprieve from your achy muscles and joints? Try taking a dip in the pool. In the water, you weigh just a tenth of what you do on land, allowing you to feel lighter and more limber. Bonus: Many women say that the cool water helps ease pregnancy stomach woes.

Just tread carefully when you’re on deck — the pool deck, that is. The slippery surface, along with your growing belly, can throw off your balance. Medical Reviewed Reviewed July 29, 2025

From the What to Expect editorial team and Heidi Murkoff, author of What to Expect When You're Expecting. What to Expect follows strict reporting guidelines and uses only credible sources, such as peer-reviewed studies, academic research institutions and highly respected health organizations. Learn how we keep our content accurate and up-to-date by reading our medical review and editorial policy.View Sources

What to Expect When You’re Expecting, 5th edition, Heidi Murkoff.
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