16 Weeks Pregnant: Baby Development, Symptoms & Signs

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4 - 5 in, 3 - 4 oz10.2 - 12.7 cm, 0.09 - 0.11 kg

24Weeks 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 16

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

At 16 weeks, you're officially 4 months pregnant!

As your second trimester hums along, your baby's growing rapidly, and you might start seeing changes to your own body too — so if you haven't already gone shopping for maternity clothes, now's the time.

Your Baby at Week 16

At a Glance

Sensitive to lightYour baby’s eyes are making small side-to-side movements this week and can perceive some light, even though they’re still closed.

The sucking reflexThat thumb-sucking habit of many newborns may have already begun. At 16 weeks, babies may be able to make sucking motions.

Strong heartBaby-to-be’s circulatory system is now up and (beginning) to run. In fact, that little heart can pump about 25 quarts of blood a day.

16 weeks pregnant is how many months?

If you're 16 weeks pregnant, you're in month 4 of your pregnancy. Only 5 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 16 weeks?

Your baby now weighs in at a whopping 3 to 4 ounces and is 4 to 5 inches in length.

The backbone and tiny muscles in your baby's back are gaining strength, so she can straighten out that head and neck even more.

Baby's eyes are working

Thanks to those developing facial muscles, your baby is capable of making a few expressive frowns and squints, even at this early stage.

Baby's beautiful eyes are finally working too, making small side-to-side movements and perceiving light, although the eyelids are still sealed. Peekaboo!

Baby's skin is transparent

Your fetus is becoming a looker too — with a face that's starting to look more human — but a skinny looker, since there's no baby fat yet.

And here's the skinny on baby skin: It's practically translucent now, so if you took a peek inside your uterus, you'd be able to see your baby's blood vessels under that thin skin.

Baby will soon hear your voice

Listen up: Tiny bones in your fetus' ears are in place, making it likely that baby will soon be able to hear your voice (or something like it) when you're speaking. Generally, babies fully develop the ability to hear in the womb by 18 weeks of pregnancy.

In fact, studies have found that babies who hear a song while they're in the womb recognize the same tune when it's sung to them after they’re born — so choose your lullabies with that in mind.

Your Body at Week 16

Rapid growth

At 16 weeks pregnant, your uterus is growing at about the same pace as your baby's — aka pretty darn fast! — and it's getting to the point where you may not be able to hide your pregnancy anymore, even if you wanted to.

You're still also likely enjoying the relative bliss of trimester two, especially compared with trimester one, and will soon be able to see more of your baby at your ultrasound in a few weeks.

Your 16 weeks pregnant belly

At 16 weeks pregnant, you may now be at the stage where your bump clearly has a baby in there. Your weight gain and that of your baby have likely picked up considerably, and you’ll both continue to grow. But all baby bumps at 16 weeks are different — and normal. Believe it or not, some women still don’t really show at 16 weeks pregnant, while others have pronounced bumps.

The wide variety of baby bumps can be attributed to everything from a woman’s size and shape to whether this is the first pregnancy or the second, third, or fourth.

Whatever you do, don’t compare your 16-weeks-pregnant belly to anyone else’s and don’t worry too much. It’s all good! If you’re still concerned, though, or have questions about how big or small you are, just talk to your doctor for some reassurance.

Your pregnancy weight gain

It may be hard to watch yourself gain weight during pregnancy, even when you know there's a wonderful reason for it, but try to embrace your body's new shape and think of every pound you put on as a sign of good health for you and your baby.

As long as you eat right during pregnancy, minimize junk, maximize nutrient-dense foods, and get regular exercise, you'll be fine in the long run. Remember, every woman gains and loses weight during pregnancy at a different pace.

One way to show your changing shape some love this week and feel better about yourself in the process: Buy a garment or accessory that makes you feel pretty at your new size — and don't forget to buy underwear that fits!

Nasal congestion

Your uterus is not the only thing that's starting to swell. So can the mucus membranes of your nose from all the pregnancy hormones circulating in your body, which are also increasing blood flow. The result? Your nose probably already knows: pregnancy congestion and possibly even nosebleeds.

Unfortunately, the stuffiness may only get worse as your pregnancy progresses, but your practitioner will probably not prescribe any medications or antihistamine nasal sprays to help clear things up. Do ask if your doctor recommends something else instead, though.

You can safely try saline sprays or nasal strips, especially if the congestion takes a turn for the truly uncomfortable. A humidifier in your room and a little petroleum jelly dabbed under your nose may also help overcome the dryness associated with any congestion.

Pregnancy Symptoms Week 16

Backaches As your belly gets bigger, your lower back curves more than usual to accommodate the load, resulting in strained back muscles. Try to soothe these sore muscles by getting a prenatal massage, even from your partner, or taking a warm bath or shower. Read More

Constipation Besides those pregnancy hormones causing your gastrointestinal tract to get sluggish, your expanding uterus is now putting pressure on your bowels, which can back things up significantly. Try increasing the amount of liquid you drink to keep everything moving along. Read More

Increased vaginal discharge Though vaginal discharge is actually beneficial to your body — it protects the birth canal from infection — it may not feel comfortable. Don’t be tempted to try douches or feminine wipes, however, since they can irritate the genital tract and lead to infection. Read More

Bleeding gums Have you noticed that your gums are bleeding after brushing? That’s because pregnancy hormones are causing gum inflammation, making them more susceptible to bacteria, irritation, and bleeding. While that's normal, it’s important to keep flossing and brushing regularly. Also see the dentist at least once during pregnancy to avoid gum disease, which can cause pregnancy complications if left untreated. Read More

Varicose veins One way to minimize the swollen blood vessels in your legs? Try to keep your weight gain healthy and gradual, and stick within the recommended range, because extra weight can increase the load on your circulatory system. Read More

Continued breast growth Wondering about your breast growth and if it will ever stop? After giving birth and weaning, if you choose to breastfeed, they should return to about their pre-pregnancy size. Read MoreTrack your symptoms with the My Journal tool in our free app

Tips for You This Week

Breast growth (and no breast growth) are both normal

Hormones and milk-producing glands are developing to prepare for nursing. All this activity, plus an increase in blood flow, can cause your breasts to grow up to three cup sizes. Of course, every pregnant woman's symptoms are different.

While breast growth is common — and for some women quite a lot — you might not notice any changes at all in your breast size, especially if you're busty to begin with. Even if you have no breast growth, it’s not cause for concern.Don’t avoid peanuts

Unless you have a food allergy yourself, you don’t have to avoid peanuts or peanut butter. The latest research suggests that eating peanuts while pregnant won’t trigger nut allergies in your baby — in fact, it may actually prevent them.

If you do have food allergies, talk to your doctor and an allergist about what you can safely eat during your pregnancy.Use a humidifier

That annoying stuffiness in your nose — and sometimes even the nosebleeds that accompany it, especially if you're blowing often — usually start around week 16 of your pregnancy.

Unfortunately, they usually stick with you and sometimes get worse until the very end. Try using a neti pot with bottled, distilled water and a humidifier to moisten your dry nose, or ask your practitioner for treatment recommendations.Embrace plant proteins

You know you need your protein, but you've had a falling out with meat (and chicken, and fish …) and now you can't be in the same room together, never mind share a plate.

You'll eventually be able to stomach these meaty foods again, but until then, pick up protein from cottage cheese, yogurt, beans, or soy products, especially tofu or edamame. Or consider quinoa, a nutty grain that packs a super-punch of protein in a comforting package.

If it's leafy greens that turn you a not-so-delicate shade of chartreuse, brighten up your diet with yellow vegetables (which are often easier to stomach), like carrots or yams. Or go for the beta-carotene in cantaloupe, mangoes, peaches, and apricots.Manage back pain

Backache got you down? Instead of nursing it on the sofa, try doing some gentle prenatal yoga or pregnancy-safe Pilates moves. Both help stretch and loosen the spine and release tension — which can be one of the main causes of back pain.

Another plus: Yoga and Pilates boost your overall energy and mood levels, so you're better able to cope with the pregnancy pains that remain.

You can also do simple moves that strengthen your abdominal muscles, which will, in turn, reduce the amount of strain on your lower back. (But remember, don't exercise on your back now that you're well into your second trimester).Go for greens

Make a habit of having a salad or grilled veggies, or sauteéd leafy greens such as spinach, escarole, or broccoli as a side.

Lentil, bean, and vegetable soups are all great choices too, and same goes for tomato-based broths and chowders.Try pelvic floor exercises

Pushing your baby through your pelvis and into the world is demanding not only on you, but also on your pelvic floor muscles — which have to stretch to proportions previously unimaginable.

Doing pelvic floor exercises during and after pregnancy can ease pregnancy symptoms and lead to a faster post-birth recovery. Squeeze the pelvic floor muscles for up to 10 seconds, shooting for three sets of 20 a day.

Building these bladder- and uterus-supporting muscles reduces your chance of bladder issues and eases a host of other pregnancy and postpartum symptoms. 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

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