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Day 144 of 280 · 20 weeks + 4 days

The cervix-length question

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

Twenty weeks and four days. Many women have their cervix measured by ultrasound between 20 and 24 weeks. Today you write down one question to ask about it.

Size this week
about the size of a banana
Length this week
around 25.6 cm from head to heel
A white woman with red hair and a small bump, in a loose denim shirt, sitting in a clinic waiting room in soft daylight, reading a handwritten question on a small notepad.

Twenty weeks and four days. Today's note is about a measurement most people have never heard of. You don't need to understand it fully; you need one question on paper before your next scan.

Your baby

A single yellow banana on a plain white linen cloth, soft daylight.

Around 25.6cm long from head to heel, about the size of a banana, and getting more active by the day: kicking, punching and turning (NHS).

Your body

Many women have their cervix length measured by vaginal ultrasound around 20 to 24 weeks (MedlinePlus). The reason is simple: the cervix typically shortens before it dilates, so its length can be an early clue to preterm labor (MedlinePlus).

Some things raise the chance of preterm labor, among them a previous preterm birth, surgery on the cervix such as a LEEP or cone biopsy, twins, and infection (MedlinePlus). Women with a prior preterm delivery may need weekly progesterone injections (MedlinePlus), and an NICHD-led study found progesterone cut the risk of another preterm birth by one third in women who'd had one before (NICHD). Whether any of this applies to you is your provider's call.

Try today

  1. The cervix-length question

    Time: 5 minutes now, 2 minutes at your visit

    1. In your notes for the next scan or visit, write: "Is my cervix length being measured, and how?" (MedlinePlus).

    2. Under it: "If it is, what does my number mean, and does anything change?"

    3. Add anything they should know: a previous preterm birth, or cervical surgery like a LEEP or cone biopsy (MedlinePlus).

    4. Write the answer down at the visit, in their words, before you leave the room.

    Make it work:

    MedlinePlus's own advice on scans is to talk to your provider about the right schedule for you (MedlinePlus). Asking isn't second-guessing anyone.

Watch for

  • Normal

    your bump tightening once in a while and then softening; some contractions through the day are normal (NICHD).

    Call your provider

    immediately for more than 5 contractions an hour, or contractions that are regular and painful (MedlinePlus).

  • Normal

    gums that bleed when you brush (NHS).

    Call your provider

    for any vaginal bleeding; in months 4 to 9, MedlinePlus says to treat it as a potential emergency (MedlinePlus).

  • Normal

    feeling hot (NHS).

    Call your provider right away

    for fever or chills, or pain when you urinate (MedlinePlus).

For you

Most people go through a whole pregnancy without ever hearing their cervix length out loud. If you're one of them, that's fine; the question still takes thirty seconds to ask. If you get a number and an explanation, you'll know more than you did, and you won't be lying awake guessing.

If a scan finds something that worries you, the NHS's advice is to talk your options through with a doctor or midwife (NHS). Bring a list, and bring someone.

If you're the partner: you're the note-taker at this one. She's lying on a table; you've got the pen.

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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