Maternity sizing: how to actually get the right fit
Sizing is where maternity shopping goes wrong most often — and where the worst advice gets handed out most freely. Here’s how it really works, so what arrives is what you hoped for. It’s also the whole reason 9Edits exists: honest, measurement-based fit guidance instead of guesswork.
Why maternity sizing is so confusing
There’s no standard pregnancy sizing. Every brand cuts differently, weight lands differently on every body, and a size 12 at one label rarely matches a 12 at another — bump room and length vary just as much as the number. On top of that, your body is changing week to week. It’s genuinely hard, and it’s not your fault that it feels impossible.
The “just size up” trap
The advice everyone gives is “just size up,” and it’s usually wrong. Good maternity ranges are designed to fit true to your pre-pregnancy size and grow with you through the bump — so sizing up can leave you drowning everywhere except the one place you needed the room. We pulled this apart in the “just size up” myth: the honest move is to check the actual chart, not reach for a blanket rule.
How to measure yourself
Three numbers do most of the work. Use a soft tape over light clothing, kept level and snug but not tight:
- Bust — around the fullest part, tape flat across your back.
- Waist / bump — your natural waist early on; later, bump room matters more than a waist measurement, so don’t worry if that number stops making sense.
- Hips — around the fullest part, feet together.
Those three, checked against a brand’s own chart, will beat guessing every single time. Numbers are only half the story, though — how you carry matters just as much, so it’s worth reading our guide to bump shapes alongside this.
Reading a brand’s size chart
Every reputable maternity brand publishes a size chart mapping measurements to sizes — but they’re all slightly different, which is exactly why one universal size never works. Find your measurements on that brand’s chart rather than assuming your usual size carries over. If you’re between two sizes, factor in the fabric: something with real stretch (jersey, rib, elastane) is forgiving, while a structured, woven piece is less so.
How 9Edits does this for you
This is the tedious part, and it’s the part we take off your plate. Share your measurements once and we compare them against each brand’s own published size chart, then show a plain “likely your fit” hint on the pieces you’re looking at — a well-informed suggestion, never a guarantee, because bodies and brands both vary. It’s the same honest thinking, applied to every item. You can read how 9Edits actually matches you, or just add your measurements and see it in action.
Sizing through the trimesters — and beyond
Your measurements will move, and that’s normal. Buy for the stage you’re in rather than the one you’re dreading — well-cut maternity pieces stretch further than you’d think. Near the end, if you plan to breastfeed, it’s worth choosing a few nursing-friendly pieces so they carry you past the birth, when your size is still settling. For the late weeks specifically, comfort tends to win outright — we wrote about what actually feels good in the third trimester.
Common questions
Do maternity clothes run big or small?
It varies by brand — there is no universal maternity size. Good maternity ranges are designed to fit true to your pre-pregnancy size and grow with you through the bump, so they shouldn’t run big everywhere. Others run small. The only reliable answer is the specific brand’s own size chart, checked against your measurements.
What size maternity clothes should I buy?
As a starting point, your usual pre-pregnancy dress size — most maternity ranges are cut to accommodate a growing bump from that base, rather than expecting you to size up. Confirm it against each brand’s size chart, because a 12 at one label rarely matches a 12 at another.
How do I measure myself for maternity clothes?
Use a soft tape, over light clothing. Measure your fullest bust, your natural waist (or, later on, note that bump room matters more than waist), and the fullest part of your hips. Keep the tape level and snug but not tight. Those three numbers, checked against a brand’s chart, beat guessing every time.
Should I size up for the third trimester?
Usually no — well-designed maternity pieces already build in room to grow, so sizing up can leave you swamped everywhere except the bump. If a particular brand’s chart suggests you’re between sizes late on, that’s the moment to consider it — but decide from the chart, not a rule of thumb.