Pregnancy Week 18: Anatomy Scan Time

Welcome to week 18 of pregnancy. Your baby has doubled in weight in less than a month, your bump is now firmly announcing itself, and you're closing in on the halfway point. This week and the next couple often bring one of the most anticipated appointments of pregnancy: the anatomy scan — sometimes called the mid-pregnancy scan, the 20-week scan or the Level II ultrasound.

It's the appointment where the sonographer looks head-to-toe at your baby's development, measures organs, checks the placenta, and — if you want to know — can often tell you whether you're expecting a girl or a boy. It's a lot to look forward to, and if you're a little nervous too, that's completely normal.

In this guide we'll cover what your baby is up to this week, what your body is likely doing, what to eat, how to move safely, exactly what happens at the anatomy scan, and questions to bring to your doctor. And a note on us: we make Vyve, a private AI pregnancy tracker that keeps your data on your phone — so consider the source — but nothing here replaces your obstetrician. This is educational, not medical advice.

Your baby this week

At 18 weeks pregnant, your baby is roughly the size of a bell pepper — about 14 centimeters (5.5 inches) from crown to rump, and weighing somewhere around 190 to 220 grams (about 7 ounces). Everything is getting bigger, but a few developments are especially cool this week:

• Ears are settling into position. Until now, the ears have been low and shifting; this week they finalize where they belong on the head. Baby can hear muffled sounds — your heartbeat, your voice, the neighbor's dog. Some parents start talking or playing music to the bump around now; it's not required, but it's not silly either.
• Nervous system is refining. Nerves are being coated with myelin — a fatty insulation that speeds up signals. This is why movements are getting stronger and more coordinated.
• Genitals continue developing. External anatomy is developed enough that many anatomy scans in the next few weeks can identify baby's sex, if you want to know.
• Yawning, hiccuping and stretching are all being practiced. You might not feel hiccups yet, but you probably will in the coming weeks — they feel like tiny rhythmic taps.
• Retinas are becoming light-sensitive. If a bright light shines on your belly, baby may be able to sense it, even with closed eyes.
• The skeleton continues hardening — a process that will keep going right through pregnancy and beyond.

The umbilical cord is thicker and stronger, and blood flow to and from the placenta is more robust — a good thing, because baby's demand for oxygen and nutrients is going nowhere but up.

Mom's body and symptoms

The second trimester is generous, but week 18 does bring some new company. Here's what many people notice:

A very visible bump. Your uterus is now roughly the size of a small cantaloupe and reaches close to your belly button. Even loose clothes probably can't hide it anymore.

Real movement, for some. If you've been pregnant before, you might feel definite kicks this week. First-timers often notice them between weeks 18 and 22, and early kicks are still subtle — an unmistakable "there it is" nudge rather than a full drum solo.

Backache. A growing bump changes your center of gravity and puts more work on lower-back muscles. Good posture, a supportive chair, sensible shoes and gentle stretching all help.

Leg cramps at night. Frustratingly common in the second and third trimesters. Stay hydrated, stretch calves before bed, and ask your doctor whether your magnesium or calcium levels warrant attention.

Heartburn and indigestion. Progesterone relaxes the valve at the top of your stomach; the growing uterus pushes upward. Smaller meals, no lying flat right after eating, and avoiding known triggers (spicy, fatty or very acidic foods) help.

Mild shortness of breath. Your heart is working harder, and your lungs have to negotiate with the diaphragm being nudged. Take stairs slower and don't apologize for it.

Dizziness. Blood volume is up, blood pressure often runs a touch lower than usual in the second trimester, and standing up fast can feel wobbly. Move slowly and eat regularly.

Skin changes. The linea nigra (a darker line down your belly), darker areolas, and small skin tags are all common. Most fade postpartum.

Swelling. A little in the ankles and feet is common. Sudden or severe swelling — especially in your face or hands — with a headache or vision changes needs immediate attention.

What isn't normal: heavy bleeding, gushing fluid, severe or one-sided abdominal pain, a bad headache with vision changes, chest pain, sudden severe swelling, or a fever. Call your obstetrician. If your dates feel fuzzy, our due date calculator can help sanity-check the timeline.

The anatomy scan, explained

The anatomy scan is the big one. It's a detailed ultrasound performed between weeks 18 and 22, usually taking 30 to 60 minutes. Here's what actually happens and why it matters.

What the sonographer checks:

• Growth measurements — head circumference, abdomen, femur length — compared to expected size for gestational age.
• Brain structures, including the ventricles and cerebellum.
• Heart — four chambers, valves, and outflow tracts. This is the most complex part of the scan.
• Spine, both length and curvature.
• Face, lips and profile.
• Kidneys, stomach and bladder.
• Arms, legs, hands and feet.
• Umbilical cord — checking that it has the expected three vessels.
• Placenta — location and health.
• Amniotic fluid — volume.
• Cervix — length, in some scans.
• Sex, if you want to know and baby's position allows a clear view.

A note on nerves: it's normal to be a little anxious. Most anatomy scans come back reassuringly normal. If something is flagged, remember that many findings are subtle, need follow-up rather than emergency action, or turn out to be nothing after a second look. Bring a support person if you can, and ask questions in real time.

Practical tips for the scan: eat and drink normally beforehand unless your clinic says otherwise (a hungry baby is often a wiggly, better-viewable baby); wear a two-piece outfit for easy belly access; bring a partner or friend; and decide in advance whether you want to know the sex, so nobody accidentally announces it before you're ready.

Nutrition tips for week 18

Nothing radical changes on your plate this week, but a few nutrients continue to earn special attention as baby grows and your blood volume expands.

• Iron. Your blood volume has grown by around 40% by mid-pregnancy. Lean red meat, chicken, fish, lentils, beans, chickpeas, tofu and dark leafy greens. Pair plant sources with vitamin C (peppers, citrus, tomato) to absorb more. Avoid coffee or tea right at mealtime.
• Calcium and vitamin D. Baby's bones are still hardening. Dairy or fortified plant milks, tofu, sardines with bones, leafy greens. Some sun and fatty fish for vitamin D, or the amount in your prenatal.
• Protein. A source at every meal — eggs, dairy, legumes, lean meats, fish, tofu, tempeh.
• DHA (omega-3). For baby's brain and eyes. Low-mercury fatty fish (salmon, sardines) twice a week, or an algae-based supplement.
• Fiber and fluids. Progesterone slows digestion, iron supplements can constipate, and things get sluggish. Whole grains, fruits, vegetables, prunes, and plenty of water genuinely help.
• Choline. Underrated for baby's brain development. Eggs are a great source.
• Small, frequent meals often beat two big ones if heartburn or nausea are back.

Still avoid: raw or undercooked meat/fish/eggs; unpasteurized dairy; high-mercury fish (shark, swordfish, king mackerel, big-eye tuna); deli meats unless steaming hot; and alcohol. Keep caffeine under 200 mg a day.

Safe exercise this week

For most healthy pregnancies, exercise stays not just safe but genuinely helpful — for mood, sleep, back pain, blood sugar, and birth prep. Aim for around 150 minutes of moderate activity a week.

Great picks at 18 weeks:

• Walking. Still the workhorse — free, flexible, adjustable.
• Swimming and water aerobics. Water takes the load off your joints and back, and many pregnant people describe it as blissful.
• Prenatal yoga. Excellent for hip mobility, breath awareness, pelvic floor and mind. Find a class labeled prenatal.
• Stationary cycling. Lower fall risk than outdoor cycling now that your balance is shifting.
• Modified strength training. Especially glutes, core (think planks, bird-dogs) and upper back — muscles that stabilize your growing bump.
• Pelvic floor and Kegel exercises. Small, invisible, and hugely worth doing regularly.

Skip or modify: contact sports, anything with fall risk (skiing, horseback riding, competitive cycling), hot yoga, scuba diving, and long spells flat on your back — modify to your left side or a slight incline. Listen for warning signs and stop if you feel pain, dizziness, gushing fluid, bleeding, contractions or extreme shortness of breath.

Questions to ask your doctor

Your prenatal visits are getting more information-packed. Use them.

• What exactly will the anatomy scan look at, and when will I get results?
• Where is my placenta positioned? A "low-lying" placenta at 18–20 weeks often moves up as pregnancy progresses; ask if follow-up is needed.
• How's my weight gain tracking? Healthy ranges depend on starting BMI. Don't guess.
• Am I on the right iron and vitamin D?
• How should I count baby's movements once they're regular? Formal kick counts usually start closer to 28 weeks, but you can ask now.
• What are my options for glucose testing? The gestational diabetes test typically happens between weeks 24 and 28 — worth previewing.
• Are my current workouts fine? Bring specifics.
• Which childbirth or lactation classes do you recommend locally?
• What warning signs should send me straight in — versus wait-and-call?

3 practical tips for week 18

1. Pre-write your anatomy scan questions. Once the ultrasound gel is on, it's easy to freeze. Even three notes on your phone — sex reveal preference, placenta location, next scan — help.
2. Invest in one truly comfortable pair of shoes. Feet swell, arches tire, and cheap shoes hurt more each week. Consider a proper pair with support.
3. Start a bump photo routine. Same wall, same angle, once a week. You'll want them later, and it takes 30 seconds.

How Vyve helps you track pregnancy privately

By week 18 you already have real notes worth keeping: how movement is starting to feel, symptoms that come and go, foods that agree or don't, weight, appointments, and questions you keep forgetting to ask. Most pregnancy apps happily collect all of that — and then quietly monetize it. That's the gap we built Vyve to fill.

Vyve is a private, on-device AI pregnancy tracker. It logs your week-by-week milestones (including anatomy scan prep and follow-up), tracks symptoms and movements without demanding a login, and turns months of your data into a clean summary you can share with your obstetrician. Everything stays encrypted on your phone. No ad targeting, no data broker deals, no baby-brand emails from companies you never gave permission to.

If you're still piecing together your pregnancy dates, or you're supporting a friend in earlier stages, our guides on the two-week wait and early signs of pregnancy might help. And curious what's next? Have a look ahead at week 19 and week 20.

Frequently asked questions

How big is my baby at 18 weeks pregnant?

At 18 weeks, your baby is roughly the size of a bell pepper — about 14 centimeters (5.5 inches) from crown to rump and weighing around 190 to 220 grams (7 ounces). Baby's ears are settling into their final position, and movements are becoming more coordinated and stronger.

What is the anatomy scan and when is it done?

The anatomy scan (also called the 20-week scan, mid-pregnancy scan or Level II ultrasound) is a detailed ultrasound usually performed between weeks 18 and 22. It checks baby's growth, examines organs including the brain, heart, spine, kidneys and limbs, measures the placenta and amniotic fluid, and — if you want to know — can often reveal the baby's sex. It typically takes 30 to 60 minutes.

What symptoms are common at 18 weeks pregnant?

Common week 18 symptoms include a growing bump that's now hard to miss, real (not just fluttery) baby movements for some, backache, leg cramps at night, mild swelling, heartburn, occasional dizziness or shortness of breath, and skin changes like the linea nigra or darker areolas. Most people still have relatively good energy compared with the first trimester.

What should I eat at 18 weeks pregnant?

Focus on iron-rich foods (lean meat, lentils, beans, spinach paired with vitamin C), calcium and vitamin D for baby's continuing bone growth, quality protein, omega-3 fats for brain development, and plenty of fiber and fluids to prevent constipation. Continue your prenatal vitamin and confirm any additional supplements with your doctor. Avoid raw or undercooked meats, high-mercury fish, unpasteurized dairy, and alcohol.

What exercises are safe at 18 weeks pregnant?

For most healthy pregnancies, walking, swimming, prenatal yoga, stationary cycling and light-to-moderate strength training are safe and beneficial around 18 weeks. Avoid contact sports, activities with fall risk, hot yoga and long periods flat on your back. Add pelvic-floor and glute work if you can — your back will thank you later. Always clear your routine with your obstetrician if you have any complications.