16 weeks pregnant: symptoms and baby development
Pulling faces, and throwing punches.
Second trimesterMonth 45 min read
By Solesia, from public clinical guidanceUpdated
A small speaker crackles, the wand slides over your belly, and then there it is: a fast, galloping rhythm, twice the speed of your own. For many people this is the week they first hear their baby, and it tends to stay with you longer than any picture. Inside, that heartbeat belongs to someone who is pulling faces, clenching fists and beginning to move on purpose rather than by reflex. You may feel more like yourself than you have in months, with one honest exception: the stairs. Your heart and lungs are working harder than they let on, and being out of breath at the top is expected.
How big is your baby at 16 weeks
About the size of an avocado
4.6 in long·4.8 oz
Baby development at 16 weeks
At 16 weeks your baby measures about 4.6 inches from crown to rump and weighs around 4.8 ounces, roughly an avocado. They are about to have a growth spurt: over the next few weeks the weight will double, and the nervous system is now developed enough that arms and legs move because they decide to, not only because a nerve fired.
The face is busy. The small muscles under the skin are working, so they smile, frown and grimace, and none of it means anything yet; it is practice for the expressions you will see later. The hands can close into a fist, and now and then they punch or grab at the cord.
The eyes are settling into their final position on the front of the face and the ears have moved up from the neck to the sides of the head. The skeleton is turning from rubbery cartilage to bone, which is why calcium matters now. You will not feel the kicks yet, but from next week some people start to.
Your body at 16 weeks
Breathlessness on stairs or a brisk walk is expected. Your blood volume has grown by a third or more, your heart is pumping more with every beat, and the hormone progesterone makes you breathe a little deeper to clear carbon dioxide for two. None of it means you are unfit. Slow down, finish the sentence when you get to the top, and keep exercising; it gets easier, not harder, with practice.
Your hands and feet may swell a little by evening, especially in warm weather. The extra fluid in your body settles wherever gravity sends it, and it drains overnight. Rings that are getting snug are easier to take off now than in a month. Feet up when you sit, and shoes with room in them, keep it comfortable.
A few people notice the first flutters this week, though 18 to 20 is more usual, and later still in a first pregnancy. Whatever you feel or do not feel is expected for now. Your bump is more obvious, and your center of gravity is beginning to shift with it, so the small ache in your lower back after a long day is the muscles adjusting. Flat shoes and a pillow between your knees at night help.
Common pregnancy symptoms at 16 weeks
- Out of breath. More blood to pump and deeper breaths to take. Slow down; it is fitness for two, not a lack of it.
- Swollen hands and feet. Extra fluid settling by evening, gone by morning. Feet up, and take tight rings off now.
- Constipation. Progesterone slows the gut and iron makes it worse. Fiber, water, a walk, and ask about a stool softener.
- Dizziness. Relaxed blood vessels let blood pool in your legs. Stand slowly and keep snacks close.
- Bleeding gums. Hormones and extra blood swell the gum tissue. A soft brush, gentle flossing, and keep going.
- Dark patches on your face. Hormones stir up pigment, and sun makes it worse. Sunscreen every morning and a hat.
- Backache. The bump is pulling your posture forward. Flat shoes, and a pillow between your knees in bed.
When to call your provider at 16 weeks
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 16 weeks
- Prenatal visit. The 16-week visit is often the first with the Doppler. It also covers blood pressure, a urine test and your weight, and it is the place to ask about screening choices before the anatomy scan.
- Quad screen. If you are having second-trimester blood screening, 16 to 18 weeks is the sweet spot for accuracy, though it can be drawn up to 22.
- Booking the anatomy ultrasound. The detailed scan happens between 18 and 22 weeks. Appointments fill up, so this is the week to get it on the calendar if it is not already.
- Childbirth class. Classes run over several weeks and fill early. Looking now means you can start in the second trimester and finish with time to spare.
Common questions at 16 weeks
When will I feel my baby move?
Usually between 18 and 20 weeks in a first pregnancy, and from 16 in a second or third, once you know what to feel for. The first movements feel like bubbles, flutters or a fish turning over, easy to mistake for gas. Nothing at 16 weeks is expected; the baby is small and the movements are still too light to register.
Can I find out the sex at 16 weeks?
Sometimes. An ultrasound can often tell from about 16 weeks, though the position of the baby decides it, and the anatomy scan at 18 to 22 weeks is the usual moment. If you had cell-free DNA screening, the result already knows, and the report shows it only if you asked.
Why do I get out of breath so easily at 16 weeks?
Your blood volume is up by a third, your heart pushes more with every beat, and progesterone makes you breathe more deeply. Stairs and hills show it first. It is expected and it does not mean you should stop exercising. Breathlessness that comes on suddenly at rest, with chest pain or a racing heart, is the version to call about.
What can the Doppler hear at 16 weeks?
Your baby’s heartbeat, at roughly 140 to 160 beats a minute, a fast whooshing gallop. Sometimes it takes a minute to find, because the baby is small and moving, and a full bladder or the position of the placenta can hide it. Not finding it on the first pass at this stage usually means nothing more than that.
Written from public clinical guidance, including NHS: Week 16, ACOG: How your baby grows, ACOG: Changes in your body, NHS: Swelling in pregnancy, NHS: Back pain and ACOG: Skin conditions during pregnancy. This page is general information, not medical advice, and does not replace your provider.