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Day 57 of 280 · 8 weeks + 1 day

The dating scan

Last reviewed · 3 min read · 6 sources · Plain-text version

The first ultrasound is due between 8 and 14 weeks. What it looks for, why it may be a vaginal scan, and the full-bladder trick.

Size this week
about the size of a raspberry
Length this week
around 16 mm from head to bottom
A Latina woman in a loose sweater sitting in a clinic waiting room with a bottle of water in her lap and a folder on the chair beside her, soft daylight from a window.

Eight weeks and one day. The dating scan can be booked from this week. Today is what it does, what it doesn't, and the one bit of preparation some clinics ask for.

Your baby

A single ripe raspberry on a plain pale wooden table, close up, soft window light.

Around 16mm, about the size of a raspberry, and the NHS adds: "By next week, they will be twice the size!" (NHS). In the first 12 weeks, an ultrasound can confirm a normal pregnancy, work out the baby's age, check the heart rate, and look for a multiple pregnancy or an ectopic one (MedlinePlus). The heartbeat usually can't be heard or seen on ultrasound until at least 6 to 7 weeks (MedlinePlus), so checking the heart rate is on the list from now on.

Your body

The NHS's first dating scan is due between 8 and 14 weeks (NHS). In the US, a first-trimester ultrasound, usually vaginal, is recommended to estimate the due date (MedlinePlus). A pregnancy ultrasound uses sound waves to picture the baby in the uterus; MedlinePlus's line is that "current ultrasound techniques appear to be safe" and that ultrasound does not involve radiation (MedlinePlus).

The practical part: you may be asked to drink 2 to 3 glasses of liquid an hour before the test and not urinate, because a full bladder gives the best image (MedlinePlus). Not every scan needs it, so ask when you book. Scans without a medical need, the keepsake kind, are something doctors advise against (OWH); the right scanning schedule for you is a conversation with your provider (MedlinePlus).

Try today

  1. The full-bladder plan

    Time: 5 minutes now, an hour before the scan later

    1. When the scan is booked, ask whether they want a full bladder for it.

    2. If yes, set an alarm for one hour before the appointment and put 2 to 3 glasses of water where you'll see them (MedlinePlus).

    3. Drink them when the alarm goes, then don't pee until after the scan; a full bladder gives the best image (MedlinePlus).

    4. Pack the appointment list and any notes about your last period; the scan is the test that sets the due date (MedlinePlus).

    Make it work:

    This early, the scan is usually a vaginal one (MedlinePlus). Ask what to expect when you book, so nothing surprises you on the day.

Watch for

  • Normal

    light cramping, on the NHS's list for the week (NHS).

    Call your provider

    right away for severe belly pain that doesn't go away; the CDC says to seek care immediately (CDC).

  • Normal

    the discharge you've always had.

    Call your provider

    for increased or foul-smelling discharge, one of MedlinePlus's first-trimester reasons to call (MedlinePlus).

  • Normal

    being a little out of breath on the stairs is not on any list, but these two are.

    Call 911

    or seek care immediately for trouble breathing, or chest pain or a fast-beating heart (CDC).

For you

The scan can move your dates. Hold the due date loosely from the start: it is only an estimate, and normal term labor can start anywhere from 3 weeks before it to 2 weeks after (MedlinePlus). If the scan says you're a few days behind or ahead of the count from your last period, the count changes; nothing else does.

If you're the partner: this is the appointment to be at. Ask whether you can be in the room, and if there's a screen, ask the sonographer to say what you're both looking at.

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.

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