Chorevia

Day 126 of 280 · 18 weeks

The anatomy scan

Last reviewed · 3 min read · 8 sources · Plain-text version

Eighteen weeks: the big scan is coming. What it checks, what it can and can't find, and the three questions worth asking before the gel goes on.

Size this week
about the size of a bell pepper
Length this week
around 14.2 cm from head to bottom
A couple in a clinic waiting room, she in a loose cardigan and leggings with a small bump, he holding a folded appointment letter, bright overhead light, no screens in view.

Eighteen weeks, and the start of your fifth month. The scan most people wait for falls somewhere in the next two weeks, so today is about knowing what it is before you're lying on the table.

Your baby

A single red bell pepper on a plain white ceramic plate, soft daylight.

Your baby is around 14.2cm long from head to bottom, approximately the size of a bell pepper (NHS). Hearing, feeling, swallowing and sucking reflexes are all developing around now (NHS). That is what the scan will be looking at: a baby with working parts, big enough to see clearly.

Your body

The ultrasound that checks for congenital anomalies is typically done between 18 and 20 weeks, and it's the one where the baby's sex can often be found (NICHD). It's worth knowing its limits going in: the anatomy scan "can detect fetal abnormalities or birth defects about half the time" (MedlinePlus). A normal scan is good news; it is not a guarantee, and an unclear picture is often just an awkward position.

Practically: you may be asked to drink 2 to 3 glasses of liquid an hour before and not pee, because a full bladder gives the best image (MedlinePlus). Check the appointment letter for what your clinic wants.

Try today

  1. The anatomy-scan questions

    Time: 5 minutes, written on the back of the appointment letter

    1. "What do you check?" The scan looks at the baby's anatomy, and later ultrasounds can also assess age, growth, position, and sometimes sex (MedlinePlus).

    2. "What happens if something is unclear?" Ask whether that means a repeat scan, a referral, or nothing at all.

    3. "Can my partner see the screen, and can we ask questions during it?" Some clinics explain as they go; others talk at the end.

    4. "Do we want to be told the sex?" The 18-to-20-week scan is when it can often be found (NICHD). Decide now so you aren't deciding mid-scan.

    Make it work:

    Hand the list to whoever is with you. You'll be watching the screen; they can watch the list.

Watch for

  • Normal

    a pulling or sharp twinge low on one side when you stand or turn; round ligament pain most often occurs between 18 and 24 weeks, and moving slowly helps (MedlinePlus).

    Call your provider right away

    for constant, severe abdominal pain, or pain with bleeding or fever (MedlinePlus).

  • Normal

    a brief head-swim when you stand up fast; your blood pressure is probably lower than usual around now (NHS).

    Call your provider

    for dizziness that doesn't pass, or any fainting; both are on the CDC's urgent warning list (CDC).

  • Normal

    spotting is not normal at this stage, so there is no "normal" line here.

    Call your provider

    about any bleeding; the NHS says it needs medical advice (NHS).

For you

If the idea of a scan makes you nervous about the scan itself, MedlinePlus is plain about it: "Current ultrasound techniques appear to be safe. Ultrasound does not involve radiation" (MedlinePlus). The AAP calls it a safe and common test (AAP).

That said, more is not better. The Office on Women's Health notes that doctors advise against ultrasound when there is no medical need, which covers the keepsake-video shops (OWH). The scans your provider orders are the ones that count.

If you're the partner: this is the appointment to move things for. Book the time off now, not the night before.

Sources

This guide is general education that summarizes published research and guidance from groups like the American Academy of Pediatrics, the CDC, and the WHO. It isn’t medical advice, and every child develops on their own timeline. Your pediatrician knows your child; if something feels wrong, call them. In an emergency, call 911.

Get each day’s note the morning it applies

Add your due date to a free Chorevia household, and every morning until the birth the day's note arrives in the app and by email: what's forming, what your body is doing, one thing to try, what to watch for, and a word for you.

Create your household