At 16 weeks pregnant, you’re officially in the second trimester and likely feeling a noticeable shift. Many of the rough first-trimester symptoms are fading, your belly is starting to show, and your baby is now about the size of an avocado. This week often brings some exciting firsts, including the possibility of feeling your baby move for the very first time.
How Big Your Baby Is at 16 Weeks
Your baby measures roughly 4.6 inches from crown to rump and weighs about 3.5 ounces (100 grams). That’s a dramatic jump from just a few weeks ago, and growth is accelerating. The legs are now longer than the arms, and the body is starting to catch up in proportion to the head.
Between weeks 16 and 20, a fine layer of hair called lanugo begins covering your baby’s skin. This isn’t the hair your baby will eventually have. It serves a specific purpose: helping a waxy, protective coating stick to the skin. That coating insulates the body and shields it from the amniotic fluid, which would otherwise irritate the delicate skin. Both the hair and the coating typically shed before birth or shortly after.
Your baby’s facial muscles are also developing enough to make expressions, though they’re not yet intentional. The nervous system is becoming more connected, and your baby is moving frequently, curling fingers, stretching limbs, and turning in the amniotic fluid.
Feeling Your Baby Move for the First Time
Sometime between 16 and 20 weeks, most women feel fetal movement for the first time, a sensation called quickening. If you’ve been pregnant before, you may recognize it as early as this week. First-time mothers more commonly notice it closer to 20 weeks, partly because the sensation is unfamiliar and easy to mistake for gas or digestion.
Women describe quickening in a variety of ways: fluttering like a butterfly, tiny tapping or pulses, bubbles popping, light rolls, or small muscle spasms. It’s subtle at this stage. You’re most likely to notice it when you’re sitting or lying still. Don’t worry if you feel nothing yet. Your baby’s position, the location of your placenta, and your own body composition all affect when you first pick up on movement.
What’s Changing in Your Body
Your uterus is growing steadily and sits roughly halfway between your pubic bone and your navel right now. It rises about two finger-widths (around 4 centimeters) each month, reaching your bellybutton by about 20 to 22 weeks. For many women, this is the point when a visible bump appears or becomes harder to conceal.
You may notice your clothes fitting differently across the hips, waist, and bust. Some women start wearing maternity pants around this time, while others get by with looser fits for a few more weeks. Breast tenderness from the first trimester often eases, though your breasts may continue to grow.
A less expected change: nasal congestion. Your nose has hormone receptors that respond to rising estrogen levels, and in some women, this causes blood vessels inside the nose to widen and produce extra mucus. The result is a stuffy nose, sometimes with nosebleeds, that has nothing to do with a cold. This is common enough that it has its own name (pregnancy rhinitis), and it can persist throughout pregnancy. Saline spray and a humidifier at night are the simplest ways to manage it.
Energy and Mood in the Second Trimester
If the first trimester left you exhausted and nauseated, you’re likely noticing a welcome improvement. The second trimester is often called the “honeymoon” phase of pregnancy for good reason. Hormone levels stabilize, nausea typically subsides, and energy returns. Many women feel more like themselves than they have in weeks.
That said, not everyone follows this pattern perfectly. Some women still deal with lingering nausea, food aversions, or fatigue. Mood swings may ease compared to the first trimester but don’t disappear entirely. The emotional landscape of pregnancy is highly individual, and there’s no “right” way to feel at any given week.
Prenatal Screening This Week
Week 16 falls within the window for an important blood test called the quad screen. This test is offered between weeks 15 and 22, but it’s most accurate between weeks 16 and 18. It measures four substances in your blood: a protein produced by the baby, two hormones from the placenta and fetus, and a fourth hormone released by the placenta. Together, these levels help estimate the risk of certain chromosomal conditions and neural tube differences.
The quad screen is a screening test, not a diagnostic one. It tells you whether risk is higher or lower than average, not whether a condition is definitively present. An abnormal result leads to further testing, often an ultrasound or amniocentesis, to get a clearer picture. Many women with flagged results go on to have perfectly healthy pregnancies, so an initial result outside the normal range doesn’t mean something is wrong.
Calcium and Nutrition
Your baby’s bones are hardening rapidly during the second trimester, which makes calcium especially important right now. The daily target for most pregnant women ages 19 to 50 is 1,000 milligrams. If you’re under 19, you need 1,300 milligrams because your own bones are still developing.
A single cup of milk, a serving of yogurt, or about two ounces of cheddar cheese each provides roughly 300 milligrams, so hitting your goal with food alone is realistic if you’re intentional about it. Calcium-fortified orange juice, fortified soy or rice beverages, canned salmon or sardines with bones, tofu made with calcium, and leafy greens like bok choy and kale all contribute meaningful amounts. If dairy is off the table, combining a few of these non-dairy sources throughout the day adds up quickly.
Your body absorbs calcium more efficiently during pregnancy, but if your intake falls short, your body will pull calcium from your own bones to supply the baby. That’s worth avoiding, especially if you plan to breastfeed afterward, when calcium demands remain high.
Sleep and Comfort
At 16 weeks, you can still sleep in most positions comfortably, but this is a good time to start getting used to side sleeping. As your uterus grows heavier in the coming months, lying flat on your back can compress a major blood vessel that returns blood to your heart. This becomes a more significant concern in the third trimester, when the weight of the uterus is substantial enough to reduce blood flow to both you and the baby.
For now, if you wake up on your back, there’s no need to panic. Simply roll to your side. A pillow between your knees and another supporting your belly can make side sleeping more comfortable and help you build the habit before it becomes medically important. Left side sleeping is often recommended because it optimizes blood flow, but either side is fine.
What to Look Forward To
Many providers schedule an anatomy scan ultrasound between weeks 18 and 22, so that milestone is just around the corner. This detailed ultrasound checks your baby’s organs, spine, heart, and limbs, and it’s typically the appointment where you can learn the sex if you choose to. Some women begin feeling regular fetal movement in the next few weeks, which provides daily reassurance between appointments. The second trimester tends to be the most physically comfortable stretch of pregnancy, so this is a good window to handle practical preparations like setting up a nursery, planning leave, or simply enjoying the relative calm before the third trimester begins.