20 Weeks Pregnant: What to Expect at Your Anatomy Scan
What the sonographer is checking
This is not just a photo opportunity — it's a systematic survey of your baby's anatomy. The sonographer measures the head, abdomen, and thigh bone to check growth, then works through the major structures one by one: brain, face, spine, heart chambers and vessels, stomach, kidneys and bladder, arms, legs, hands and feet. They also check where the placenta sits, how much fluid surrounds your baby, and (where offered) the cervix length. In this video I walk through each check so you know what the silence and the clicking mean while you watch the screen.
Preparing for the appointment
- Arrive with a comfortably full bladder if your clinic asks — it lifts the uterus for a clearer view early in the scan.
- Bring your partner or support person — most clinics welcome one guest, and this is the scan you'll both remember.
- Expect it to take a while. Babies don't always cooperate; you may be asked to walk around or return another day to finish a view. That's normal and not a sign of trouble.
- Decide beforehand about finding out the sex — you'll be asked, and it's much easier to have the conversation at home first.
If something is flagged
Roughly 1 in 50 scans finds something that needs a follow-up — very often a 'soft marker' that turns out to be a normal variant. You'll usually be offered a referral to a specialist unit and sometimes extra tests. Being flagged means your team wants better information, nothing more. Ask questions, take the leaflets, and don't sit alone with Google — your care team has seen your exact situation many times.
Common questions
Is the anatomy scan safe?
Yes. Ultrasound has been used in pregnancy for decades with no evidence of harm to mother or baby, and this scan is a standard part of care in Canada.
Can the scan detect everything?
No scan detects everything — roughly half to two-thirds of major structural differences are picked up, varying by condition. A normal scan is very reassuring, but no test guarantees a baby with no health conditions.
What if my placenta is low?
A low-lying placenta at 20 weeks usually moves up as the uterus grows — most resolve on their own. You'll be offered a follow-up scan around 32–36 weeks to confirm, and in the small number of cases where it stays low, birth is planned by caesarean.
How Twins, Triplets and More Are Made
Next, a special kind of pregnancy: how twins, triplets, and more are made.