21 weeks pregnant: symptoms and baby development
They can hear voices from outside now.
Second trimesterMonth 55 min read
By Solesia, from public clinical guidanceUpdated
The bubbles stop being bubbles this week. What was a flutter you had to hold still to notice is now, unmistakably, a small person turning over, and a partner with a hand on your belly may soon catch one from the outside. Your baby can hear voices beyond your body for the first time, so talk to them if you like, and they now weigh more than the placenta that feeds them. For you, the second-trimester glow shares the week with a returning tiredness and joints that have gone a little loose, so balance and a good night’s sleep both take a bit more effort.
How big is your baby at 21 weeks
About the size of a carrot
10.5 in long·14.4 oz
Baby development at 21 weeks
At 21 weeks your baby measures about 10.5 inches from head to heel and weighs around 14.4 ounces, roughly a carrot. For the first time they outweigh the placenta, which until now has been the bigger of the two; from here the baby pulls ahead every week.
The ears are finished enough that sounds from outside get through: voices, music, a door closing. They are muffled by your body and the fluid, but the rhythm and pitch of your voice come through well, and a sudden loud noise makes them jump.
They are developing a rhythm of waking and sleeping, though it rarely lines up with yours; a baby who is quiet all day and busy the moment you lie down is being entirely normal. Lanugo, the fine downy hair, covers the body, and the eyebrows are in. Sucking and swallowing are getting practiced, and the bone marrow has begun making blood cells, a job the liver and spleen have been doing until now.
Your body at 21 weeks
Kicks that you can feel clearly are expected from about now, and they get stronger week by week. They are often clearest when you are still: lying in bed, sitting after a meal, in a quiet room. At 21 weeks there is nothing to count. You are getting to know your baby’s habits, and by 24 to 28 weeks you will have a sense of their pattern.
Your joints are looser, thanks to the hormone relaxin, and your center of gravity has moved forward with the bump, so you may feel unsteady on stairs, in the shower or on ice. This is expected. Hold the rail, wear shoes that grip, and take your time. Backache from the same shift is common; the muscles are learning a new posture, and a warm bath and a pillow between your knees at night help them recover.
Tiredness can come back in the second half of pregnancy, partly because sleep is broken by the bladder, the bump and the kicks, and partly because you are carrying more every day. Twenty minutes in the afternoon makes a real difference. Breasts may leak a drop or two of colostrum, the thick first milk, and pads in your bra handle it. Hemorrhoids, swollen veins around the anus, are common as the uterus presses on the pelvis; fiber, water and not straining keep them quiet.
Common pregnancy symptoms at 21 weeks
- Backache. A forward-shifted bump and loose ligaments. A warm bath, flat shoes, and a pillow between your knees in bed.
- Feeling unsteady. Relaxin loosens joints and the bump moves your balance. Shoes that grip, and hold the rail.
- Tiredness. Broken nights and a heavier load. A short afternoon nap, and an early night when you can.
- Hemorrhoids. Swollen veins from pressure and constipation. Fiber, water, no straining; a cream from your provider if sore.
- Leaking breasts. Colostrum, the first milk, arriving early. Breast pads; nothing else needs doing.
- Swollen hands and feet. Fluid settling by evening. Feet up when sitting, and comfortable shoes.
- Heartburn. A squeezed stomach and a relaxed valve. Small meals, nothing heavy before bed.
When to call your provider at 21 weeks
If you have a fall, even a small one, let your provider know the same day, just so they can check.
Two things are worth a same-day call at any point in pregnancy: bleeding that is more than spotting, and pain that is severe or does not ease. From the second trimester, add fluid leaking and any change in your baby’s usual pattern of movement. You do not need to be sure something is wrong to call; that is what the number is for.
What to do at 21 weeks
- Anatomy ultrasound, if not done. The window runs to 22 weeks, so this week or next is the last comfortable slot. If you had it already, this is a good week to ask about the results, including where the placenta sits.
- Naps. Nights are getting broken. A short sleep in the afternoon, or simply lying down for twenty minutes, is the habit that gets many people through the second half.
- Pelvic floor exercises. Ten slow squeezes and ten quick ones, three times a day. The weight on the pelvis is increasing, and the muscles that hold everything up need the practice.
- Travel plans. Weeks 14 to 28 are the easiest for a trip. Airlines allow flying until late pregnancy, but many want a note from 28 weeks, so a vacation is best taken now.
Common questions at 21 weeks
How often should I feel my baby move at 21 weeks?
There is no number yet. At 21 weeks movements come and go, busy spells and quiet ones, and it is expected to go hours without noticing anything, especially when you are up and about. From 24 to 28 weeks you will know your baby’s own pattern, and that pattern is what matters.
Can my partner feel the baby kick at 21 weeks?
Sometimes, and more often over the next few weeks. Kicks are getting stronger, but they have to reach through the uterus, the fluid and your belly, so the first ones a hand can catch are usually between 22 and 26 weeks. Evening, lying down, with a hand resting low on the bump, gives the best odds.
Why am I tired again in the second trimester?
Sleep is being broken by your bladder, the bump and the kicks, and you are carrying more weight every week. Iron can play a part too; a low count is common in the second half of pregnancy and easy to check with a blood test. Naps, an earlier bedtime and iron-rich food help.
Can I fly at 21 weeks?
Yes. The second trimester is the easiest time to fly: nausea has passed and the bump is not yet in the way. Drink water, walk the aisle every hour or so, and wear the seat belt under the bump. Check your airline’s rule; many ask for a provider’s note from 28 weeks and set a cutoff around 36.
Written from public clinical guidance, including NHS: Week 21, ACOG: How your baby grows, ACOG: Changes in your body, NHS: Your baby’s movements, NHS: Tiredness and NHS: Back pain. This page is general information, not medical advice, and does not replace your provider.