Fetal Development 16 Weeks | What Your Baby Is Doing

Week 16 often feels like a turning point. Nausea may ease, your bump may start to show, and your baby keeps growing fast inside the uterus.

Inside the womb your baby is building organs, strengthening bones, and practicing small movements that prepare for life after birth. This overview of week 16 fetal development explains what is happening with your baby and what you may notice in your own body.

Fetal Development 16 Weeks: Baby Size And Milestones

By 16 weeks of pregnancy, your baby is often compared with an avocado or a large orange. Resources such as the American Pregnancy Association describe an average crown-to-rump length of around 11 to 12 centimeters and a weight close to 100 grams or about 3.5 to 4 ounces.¹ Every pregnancy varies, so a slightly smaller or larger baby can still be healthy.

How Big Is Your Baby At 16 Weeks?

Growth during the second trimester speeds up. According to the UK National Health Service guidance for 16 weeks, babies at this point are long and lean, with room to move since the uterus still has plenty of space.²

Ultrasounds around this time use several measurements, not just head-to-bottom length, to check that growth fits your due date.

What Your Baby Looks Like Now

Your baby now looks much more like a newborn than a tiny embryo. The eyes and ears sit close to their final positions, the neck is more defined, and the head no longer dominates the whole body.³ Arms and legs are longer, joints bend easily, tiny fingernails and toenails appear, and a thin layer of soft hair called lanugo may start to form on the skin.

Organs, Bones, And Nervous System

Several major organ systems are working in simple ways. The heart is strong enough to pump many quarts of blood each day through the small body, moving oxygen and nutrients where they are needed.³ The urinary system produces urine that becomes part of the amniotic fluid, the digestive tract moves swallowed fluid along, and the skeleton is shifting from soft cartilage toward firmer bone so movements gradually become smoother and more coordinated.

Senses, Movement, And Early Patterns

Many parents wonder whether a baby can hear or feel at 16 weeks. Hearing is still early in its development, but tiny bones in the middle ear are forming and nerve routes from the inner ear to the brain are taking shape, as outlined by the Mayo Clinic.⁴ Within a few weeks, your baby may start reacting to muffled sounds from outside the womb.

Touch sensitivity also improves as nerve endings spread across the skin. Your baby may brush hands against the face or press gently against the uterine wall, movements that help the brain build connections.

Will You Feel Kicks Yet?

At this stage your baby moves often, but many first-time parents still do not feel clear kicks. The baby is small, cushioned by fluid, and may face the back of the uterus, so movement can feel like faint bubbles or taps. If you feel nothing yet, that is usually normal; regular prenatal appointments and any recommended ultrasounds give more reliable information about fetal development at 16 weeks than day-to-day sensations.

Fetal Development At 16 Weeks: Changes In Your Body

While fetal development at 16 weeks moves quickly, your own body changes right alongside the baby. Many people notice a small round bump, changes in breast size, and a shift in energy levels during this part of the second trimester.

Common Physical Changes

As the uterus grows upward, you might feel stretching or mild cramps on one or both sides of the lower abdomen. These sensations often come from ligaments that hold up the uterus. Gentle movement, changing position, and staying hydrated can ease this discomfort.

Increased blood volume can bring a warm glow to the skin but also nasal congestion or occasional nosebleeds. Some people notice more vaginal discharge, which is usually thin or milky. Strong odor, itching, or pain, though, should prompt a call to a healthcare provider.

Emotional Shifts Around Week 16

The end of the first trimester often brings some relief from nausea and fatigue, yet mood can still swing from calm and joyful to worried or tearful. Hormone shifts and pregnancy-related stress both play a part.

If low mood, anxiety, or intrusive thoughts linger for more than two weeks, speak with your midwife, obstetrician, or another trusted professional. Early care for mental health helps both you and the baby over the rest of the pregnancy.

Week 16 Development Snapshot

Feature	What Is Happening	What It Means For You
Baby length	About 11–12 cm crown-to-rump, similar to an avocado or large orange	Fundal height and scans track growth.
Baby weight	Around 100 g or 3.5–4 oz on average	Weight rises quickly through the second trimester.
Skeleton	Cartilage turning into stronger bone	You may feel sharper kicks later this month.
Heart and blood flow	Heart pumps many quarts of blood each day through tiny vessels	Doppler or ultrasound can pick up a fast heartbeat.
Nervous system	Nerves connect muscles and brain, shaping smoother movement	Frequent motion is positive, even if you cannot feel it yet.
Skin and hair	Thin skin and early lanugo form a base for later protection	Hair and protective coatings build over coming weeks.
Face and senses	Eyes and ears move into place; hearing structures develop	Your baby will soon react to your voice and other sounds.

Prenatal Visits And Screening Around 16 Weeks

Many antenatal schedules include a visit around week 16 to review test results from early pregnancy, check blood pressure, and listen to the fetal heartbeat. Your midwife or doctor may ask about pain, bleeding, or unusual discharge and invite any questions you bring.

Some people are offered second-trimester blood tests that screen for certain chromosomal conditions or open neural tube defects, and a detailed anatomy scan often follows between 18 and 22 weeks. Exact timing varies by country and health system, so your care team can explain benefits, limits, and possible next steps before you decide which tests feel right for you.

Caring For Yourself At 16 Weeks

Day-to-day choices still matter a lot while fetal development 16 weeks progresses. You do not need a perfect routine, but a few steady habits can help both your body and your growing baby.

Eating And Drinking

Many people feel hungrier during this trimester, so regular meals and snacks rich in protein, fiber, and healthy fats can keep energy steadier. Official guidance from national health agencies, such as the NHS advice on foods to avoid in pregnancy, recommends limiting high-mercury fish, unpasteurised dairy, and undercooked meat to lower infection and toxin risks.^2,5 A varied diet plus a prenatal vitamin chosen with your healthcare provider usually covers most nutrient needs; if nausea or food aversions make eating difficult, talk with your provider early.

Movement, Rest, And Everyday Life

If your pregnancy is low risk, gentle activity such as walking, swimming, or prenatal yoga often feels good and helps with sleep, digestion, and back comfort. Most guidelines suggest at least 150 minutes of moderate movement each week, adjusted for your starting fitness level and any medical advice you receive, while regular rest and comfortable side-lying sleeping positions with pillows between the knees can ease strain on your back and hips as your bump grows.

Week 16 Checklist For You And Your Baby

Area	Simple Action	Why It Helps
Prenatal care	Attend your scheduled week 16 visit and ask questions	Tracks growth, blood pressure, and lab results
Nutrition	Plan meals with protein, whole grains, fruit, and vegetables	Supplies fuel for rapid fetal growth
Hydration	Keep a water bottle nearby and sip through the day	Can reduce constipation, headaches, and false contractions
Movement	Choose light activity most days if your provider agrees	Can help circulation, mood, and sleep
Sleep	Use pillows to find a comfortable side-lying position	Takes pressure off major veins and the lower back area
Mental health	Share worries with people you trust or a professional	Early care lowers the risk of deeper distress later

When To Contact A Healthcare Provider At 16 Weeks

Most pregnancies progress smoothly through the second trimester, yet some symptoms need prompt medical attention. Get urgent care or call emergency services if you have heavy vaginal bleeding, severe abdominal pain, sudden loss of fluid from the vagina, or chest pain and trouble breathing.

Contact your midwife or doctor the same day if you notice steady cramping that does not ease with rest, burning pain when you urinate, fever, strong headache, vision changes, or swelling of the hands and face, since these signs can signal infection, high blood pressure, or other problems that need review.

If a screening test result worries you, ask the provider who ordered it to explain what the numbers mean and what follow-up is available.

What Comes Next After Week 16

Over the next few weeks, most people start feeling regular movement, sometimes called quickening, as the baby grows stronger and takes up more space. By around 20 weeks, many receive the detailed anatomy scan that shows the brain, heart, spine, kidneys, and limbs in far more detail.

Fetal development 16 weeks into pregnancy lays the base for many of those later milestones. Growth will continue all the way to birth, and the mid-pregnancy stage often brings more energy, stronger connection with the baby, and clearer check-ins at prenatal visits.