Maternity Jeans Sizing Guide

What size maternity jeans should you buy?

Why pre-pregnancy size is the rule

Maternity denim is a different pattern, not a bigger one. The panel adds the room the bump needs, and the rest of the garment is cut for the body you had before — hips, thighs, seat, inseam.

So sizing up does two unhelpful things: it adds width where the panel was already handling it, and it adds width at the thigh and seat where you did not ask for any. The result is jeans that are simultaneously baggy and no more comfortable at the bump, which is the commonest sizing mistake in the category.

There is one genuine exception. If your hips and thighs have changed substantially — which happens, and is normal — then sizing up reflects a real change rather than a guess about the bump. Measure rather than assume.

How to measure

Three numbers, and you can get all of them from clothes you already own.

Measure in the morning if you can. Swelling means evening numbers can be larger, particularly later in pregnancy, which the NHS lists among the ordinary features of pregnancy.

Rough size conversion

Most maternity brands use letters or a numeric size matched to pre-pregnancy sizing. As an orientation rather than a promise:

This is an orientation table, not a rule. Letter sizing in maternity is graded differently by every brand, which is exactly why the chart on the listing beats any general table including this one.

Where maternity sizing is genuinely unreliable

We would rather say this than pretend to a precision we do not have.

• Letter sizing is brand-specific. An L from one brand is not an L from another, and there is no industry standard to appeal to.
• Panel height varies and is rarely stated. Two over-belly jeans in the same size can have panels two inches different in height, which changes everything about whether it rolls.
• Inseam is usually a single unstated number. Most brands do not publish it, which is why length is the hardest thing to get right.
• Stretch content is rarely specified usefully. “Stretch denim” covers a wide range, and it determines how much a size error matters.

Where reviews consistently report a brand running small or large, that is real signal and worth believing. Where we do not know how a brand runs, we say so rather than guessing — which is the standard set out in how we pick.

What to do if you are between sizes

• For over-belly styles, size down. The panel is designed to stretch, and a loose over-belly panel rolls and slides.
• For side-panel styles, size up. Side inserts have limited stretch and they run out, so a little extra room buys you weeks.
• For inseam, go longer. The front hem rises as the bump grows, because the panel pulls the waist up at the front.
• Buy a relaxed cut. Ease through the hip and thigh means half a size either way is not the difference between wearable and not.

When to buy

Buy in the second trimester, not the first. Jeans bought at 10 weeks are usually bought for bloating rather than a bump, which is a different shape and a different size.

Buy in two rounds rather than one. Your measurements at 30 weeks are not the ones you are shopping with at 16, and a single large order early is the most reliable way to end up with clothes you cannot wear. Our timing guide goes through the stages.

What size afterwards?

Worth knowing in advance. Most people are not back in their pre-pregnancy jeans for some months, and a lot of people never go back to exactly the same size — hips and rib cage sometimes settle slightly differently, which is normal and not a problem to solve.

That makes maternity jeans with side panels the ones most likely to keep being worn afterwards, because they read as ordinary denim once the panel is less obviously needed. And an over-belly rise is the most comfortable thing over a caesarean scar in the early weeks.