21 Weeks Pregnant Baby Size

21 Weeks Pregnant: Your Baby’s Development

This week, your baby's heartbeat is now loud enough to be heard through a simple stethoscope, but the beat can be difficult to distinguish from your own. Listen for the faster rhythm — a baby's heartbeat is 120 to 160 beats per minute, about twice as fast as yours. Many women think it sounds like galloping horses.

Your baby is already starting to sleep and wake in subtle cycles. Ultrasounds show that unborn babies may even settle into a favorite sleeping position.

At around 21 weeks, your little one’s fingers and toes are completely formed, complete with little fingerprints and toe prints. If you were to have an ultrasound this week, you may even catch your baby sucking on a thumb.

By now, your baby’s digestive system is developing, and she’s now able to swallow small amounts of amniotic fluid, which can be absorbed by the intestines. Her little liver and spleen have been making blood cells, but now, the bone marrow can create blood cells, too. Eventually, the liver and spleen will stop producing these blood cells before birth.

The Size of the Fetus at 21 Weeks Pregnant

When you’re 21 weeks pregnant, your fetus is roughly the size of a banana.

This illustration can help you envisage what your little one may look like this week:

21 weeks pregnant

Mom’s Body at 21 Weeks

So, when you get to 21 weeks pregnant, how many months along are you? At 21 weeks, you’re almost six months pregnant.

You may have had some heartburn and indigestion earlier in the first trimester, but as your uterus gets larger, it may start pushing up against your stomach. This can cause you to have heartburn more frequently.

Around this time, your pregnancy hormones may also cause hot flashes, and the extra weight can cause some aches and pains during the coming weeks.

21 Weeks Pregnant: Your Symptoms

At 21 weeks pregnant, here are some of the symptoms you may be experiencing:

  • Sore spots. Backaches, especially in the lower back, are quite common during pregnancy. When you are 21 weeks pregnant, your growing belly is shifting your center of gravity and pulling your lower back forward. Meanwhile, the hormone relaxin is loosening every joint and ligament in your body, which will allow your pelvis to expand when it's time for delivery.

  • Heartburn. Around this week, it’s normal to experience heartburn. In addition to the uterus pushing against your stomach, pregnancy hormones relax the valve between your esophagus and stomach, causing some stomach acid to leak into the esophagus.

  • Hot flashes. Your pregnancy hormones and your increased metabolism can leave you feeling hot and sweaty. Make sure you stay cool by wearing loose clothing and drinking plenty of water. Switch on a fan or crank up the air conditioning, and try to stay as comfortable as possible.

  • Stretch marks. As your belly grows during your pregnancy, you may notice some reddish-brown, pink, or purple lines on your skin. Stretch marks form when your skin stretches over a short period of time and can appear along your belly, hips, thighs, buttocks, and breasts. Your skin may start to feel itchy, too; applying moisturizer should help.

  • Leg cramps. If you feel any cramping in your legs, don’t worry; this a common complaint from moms in the second trimester. You may notice that cramps tend to strike more at night. Try to stretch your calf muscles before bed, drink plenty of water, or have a warm bath or shower to help ease the discomfort or prevent cramping altogether.

21 Weeks Pregnant: Things to Consider

  • To help alleviate back pain, make these adjustments in your daily routine. Whenever you sit, use a footrest to elevate your feet slightly. If you need to stand for a long period of time, put one foot on a small stool to take some pressure off your lower back. Treat yourself to a warm bath for additional relief. If your backache won't go away, give your healthcare provider a call.

  • The B vitamins, including B1, B2, and B6, are key nutrients because they supply energy for your baby’s development. They also help promote good vision and help build the placenta, along with other body tissues. If you’re taking a prenatal supplement, you should be getting enough B vitamins already, but you can also get them from dietary sources like liver, pork, poultry, bananas, and beans.

  • Choline is another nutrient you may need more of when you’re pregnant. Even though your body can produce choline naturally, when you’re pregnant, you’re not making enough for the two of you. This is easy to top up with a balanced diet, so try to add more chicken, beef, eggs, milk, and peanuts, all of which will help supplement your choline levels. You can read more about nutrition in our downloadable pregnancy guide.

  • As your uterus gets bigger, you may notice your center of gravity shifts, and you may feel a little off balance. Take care of yourself by wearing flat shoes, being careful on stairs, and avoiding slippery surfaces to reduce the risk of falling. If you do fall and you’re concerned, if you’re bleeding, or if you start experiencing contractions, contact your healthcare provider.

  • The next couple of months are a good time to get some preparations out of the way, especially as your energy levels might dip come the third trimester. Things like getting your baby’s nursery ready, writing a list of all the baby gear you’ll need, and creating a baby budget are all things you can start now, if you haven’t already.

  • Even as your pregnancy progresses, doing some movement is important for your body and can help with how you’re feeling as well. Speak to your healthcare provider if you’re unsure about what exercise is safe for you to do at this stage. Typically, things like walking, prenatal yoga, and swimming can still be good options.

  • If you discovered you were expecting twins during an earlier ultrasound, read our FAQ on twin pregnancy and our article on how a twin pregnancy is unique week by week.

21 Weeks Pregnant: Ask Your Doctor

  • What are the signs of gestational diabetes and are you at risk?

  • Can a maternity belt help with back pain?

  • Do you need to increase your intake of nutrients like choline and B vitamins as part of your diet?

  • What is a doula, and should you consider hiring one for labor and delivery?

21 Weeks Pregnant: Your Checklist

  • Get a footrest to elevate your feet slightly whenever you sit.

  • Treat yourself to warm baths to help relieve back pain.

  • If you haven’t already, sign up to a childbirth class.

  • Make sure your baby registry is done, especially if your baby shower is happening soon.

  • If your partner hasn’t already, it may be time to start looking into paternity leave.

  • Sign up for even more weekly pregnancy tips.

How We Wrote This Article
The information in this article is based on the expert advice found in trusted medical and government sources, such as the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.

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