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21 Weeks Pregnant: Week by Week Pregnancy

Symptoms, Tips and Fetal Development


The second trimester is about halfway over when you are 21 weeks pregnant. Although there are a lot of unseen changes going on with your body and your baby when you’re 21 weeks pregnant, chances are you’re feeling pretty good at this stage in your pregnancy. With no major tests or ultrasounds on the schedule, you can relax and enjoy being pregnant at 21 weeks. Here’s what to expect when you’re 21 weeks along.

Baby at 21 weeks pregnant

Here’s a new term: crown to heel, which replaces the previously used crown to rump measurement. This week, your baby is charting at 10.5 inches, or about the length of a large carrot, and weighing in at between 11-13 ounces.

Your baby’s movements are becoming more coordinated and less jerky thanks to three developments: 

  • The formation of bones throughout the body
  • Arms and legs that are finally in proportion
  • Neuron connectivity between the brain and the body’s muscles

Plus, fat is beginning to develop under your baby’s thin skin and his/her bone marrow is making blood cells. Your little’s digestive system is functioning at a basic level, although s/he is still completely dependent on the placenta for nourishment. Also noteworthy during pregnancy week 21: a baby’s anal sphincter becomes fully functional, woot!

You might have heard that the flavors you eat during pregnancy can affect your baby’s food preferences after birth. That’s because your baby is tasting a little amniotic fluid every day as s/he practices swallowing and digesting, and the flavor of the amniotic fluid reflects in part the food you’ve been eating. So here’s your first chance to start pushing the green veggies, mama!

Your body at 21 weeks pregnant

Many women who are pregnant at 21 weeks find that they're having a hard time sleeping at night. This is partly because of the changes in your body, but also because your baby could be most active at night. Many babies develop an activity routine and you may eventually be able to predict when your baby is sleeping and when she's awake.

When you're 21 weeks pregnant, there’s no denying your changing body. In addition to the weight gain of about a pound a week, your rib cage is enlarging to accommodate your increasing lung capacity. In fact, by the time your baby is born, your rib cage will have expanded by two to three inches! Not to worry, it will return to its pre-pregnancy size after birth. 

pregnancy week 21 embryo
Weekly development of a human fetus at 21 weeks pregnant.

By the time you’re 21 weeks pregnant, your estrogen levels finally catch up to your progesterone levels. You can expect your blood pressure to remain lower than normal for another few weeks. It's normal to develop a clear or white vaginal discharge when you're pregnant at 21 weeks. If this discharge thickens or becomes yellow, you should mention it to your healthcare provider since these are signs of infection.

21 weeks pregnant ultrasound

Most women have a thorough anatomy scan ultrasound between 18-20 weeks. Speak to your doctor about scheduling this ultrasound if you haven’t completed it yet.

How big is my baby at 21 weeks?

two carrots, portraying the size of a 21 week human embryo

At 21 weeks pregnant, your baby is the length of a carrot, on average measuring at 10.5 inches long and weighing on average 11-13 ounces.

21 weeks is how many months pregnant? 

At this stage in your pregnancy, you're 5 months 1 week (5m1w) pregnant. 

Common symptoms at 21 weeks pregnant

Here are some of the symptoms you might expect at 21 weeks pregnant.

  • Nasal congestion, nosebleeds, and bleeding gums: With your circulatory system still expanding, and blood production continuing at rapid rates, you might be seeing the effects in the form of nosebleeds, bleeding during tooth brushing, and a stopped-up nose. Also, your blood pressure remains on the low side.
  • Sluggish digestion: Pregnancy hormones may continue to wreak havoc on your digestive system, resulting in constipation, heartburn, and indigestion.
  • Breathlessness: Despite a respiratory system that’s pulling 20% more air into the lungs, many pregnant women continue to experience some breathlessness.
  • Swollen breasts: As your body prepares for breastfeeding, your breasts might have increased two full cup sizes at this point and be boasting a veritable road map of blue veins. You might even be noticing a few drops of colostrum, or the first breast milk, from your nipples. 
  • Waddling posture: By now your weight gain has changed your center of gravity. To help your posture, consider getting some gentle exercise, such as swimming or walking.
  • Aching belly and leg cramps: Being 21 weeks pregnant means that you might start feeling aches in your belly, caused by your growing uterus. Leg cramps and backaches can also become more frequent as your pregnancy progresses.
  • Skin pigmentation: Skin pigmentation, such as the linea nigra on your belly, is a common side effect of pregnancy. Any pigmentation will fade and most likely completely disappear after pregnancy.
  • Increased libido: Many women notice they feel “in the mood” more often during the second trimester. Unless your doctor says otherwise, sex is safe during pregnancy
  • Increased appetite: As nausea fades, you might be feeling hungrier. Pregnant women need about 300 additional calories per day (so not a lot, really!). Aim to use them on nutrient-rich foods that benefit fetal development (with a few treats now and then of course!).
  • Blurred vision: This is caused by water retention and generally disappears after birth. During pregnancy is not the time to get a new prescription or undergo eye surgery, lest you overcorrect your regular vision for your pregnancy vision!
  • Dry eyes: Hormones are to blame if you’re experiencing decreased tear production. Your eyes may feel dry and it can make wearing contacts less comfortable.

Pregnancy checklist at 21 weeks pregnant 

A few things to do and consider when you’re pregnant at 21 weeks.

  • Prepare for prenatal care: Now that you're pregnant at 21 weeks, prenatal visits may start happening more frequently, especially if you are expecting more than one baby. However, some healthcare providers will continue with the once a month visits, at least for another few weeks.
  • Seek relief from swelling: If you're having problems with your feet and ankles swelling, give maternity stockings a try. These can help boost circulation through your legs and feet and provide some much-needed relief. A massage can also help, plus it can unwind you if you're feeling stressed. Make sure to let the massage therapist know that you're pregnant so you can have a special "pregnancy massage."
  • Register for classes: If you've been putting off signing up for childbirth class, now is the time. There are different types and different philosophies/methods, ask your doctor. Look for a class taught by a certified childbirth educator. If this is your first baby, maybe you also want to sign up for baby care, breastfeeding, and car seat installation classes. 

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