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Day 111 of 280 · 15 weeks + 6 days

Book the big scan

Last reviewed · 3 min read · 10 sources · Plain-text version

The anatomy scan usually falls between 18 and 20 weeks. Today you confirm the date, decide who's coming, and learn what it can and can't see.

Size this week
about the size of an apple
Length this week
around 10.1 cm from head to bottom
A Black couple on a sofa, the woman in a loose shirt with a paper calendar on her knee, her partner leaning in to point at a date, warm lamplight in the evening.

Fifteen weeks and six days. The last day of week 15, and a good day to pin down the one appointment in the next month that nobody should miss.

Your baby

A single red apple on a plain pale wooden table, soft window light.

Around 10.1cm from head to bottom, about the size of an apple (NHS). In a few weeks a scan will look at this body in detail: the ultrasound to check for congenital anomalies is typically done between 18 and 20 weeks, when the baby's sex can often be found as well (NICHD). Later ultrasounds assess the baby's age, growth and position, and can identify developmental problems (MedlinePlus).

Your body

The scan is of you as much as the baby: around 20 weeks it checks the baby's anatomy, and it "can detect fetal abnormalities or birth defects about half the time" (MedlinePlus). That number is worth holding on to in both directions. A clear scan is reassuring but not a guarantee, and a scan can't see everything. The NHS's week 20 page says the anomaly scan may happen that week and includes an examination of the placenta (NHS).

On the day, you may be asked to drink 2 to 3 glasses of liquid an hour beforehand and not urinate, because a full bladder gives the best image (MedlinePlus). The test itself uses sound waves, not radiation, and "current ultrasound techniques appear to be safe" (MedlinePlus); the AAP calls it a safe and common test (AAP). If the scan brings worrying news, the NHS says to talk through the options with a doctor or midwife (NHS).

Try today

  1. The anomaly-scan booking

    Time: 10 minutes

    1. Find the date. If it isn't booked, ask the office for a slot between 18 and 20 weeks (NICHD).

    2. Write it where both of you will see it, and block the two hours around it.

    3. Decide who's coming. Ask the office how many people the room allows and whether children can come.

    4. Decide now whether you want to be told the sex, so the sonographer can be asked at the start (NICHD).

    5. Ask about the bladder instructions for your clinic, so you aren't guessing on the morning (MedlinePlus).

    Make it work:

    Book the time off work now, not the week before; the NHS lists paid time for antenatal appointments among your maternity rights (NHS).

Watch for

  • Normal

    a little white, milky discharge (NHS).

    Call your provider

    for any bleeding; the NHS says to seek medical advice for it at any stage (NHS).

  • Normal

    damp underwear from discharge rather than anything else.

    Call your provider as soon as you can

    for fluid leaking from the vagina (OWH); vaginal bleeding or fluid leaking is on the CDC's urgent list (CDC).

  • Normal

    a brief jab in the side of the bump that eases with rest (NHS).

    Call your provider right away

    for moderate to severe cramping or low abdominal pain (MedlinePlus).

For you

One scan you don't need to book: the keepsake kind. Doctors "advise against ultrasound when there is no medical need to do so" (OWH). The right number of scans is a conversation with your provider, not a shop (MedlinePlus).

If you're the partner: if you only make one appointment in this whole pregnancy, make it this one. It is the longest look either of you will get before the birth, and it's also the one where news, if there is news, arrives. Don't let her sit in that room alone.

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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