Most women start wearing maternity clothes between weeks 12 and 20 of pregnancy, though the switch is personal, prompted by trousers that no longer fasten. In a second pregnancy, most women change earlier - commonly from around week eight.
The week of change is different for everyone
Ask ten women when they started wearing maternity clothes and you will get ten different answers. Someone at your antenatal class was in maternity jeans at eleven weeks. Someone else made it to twenty-four with the top button undone and a hair tie doing work under a jumper.
Both are normal. The range most women fall into is weeks 12 to 20, with the NHS noting that most pregnancy weight gain happens after week 20, which is why the second trimester tends to be when things shift. But bloating, softening ligaments and a ribcage that quietly expands all start changing the way clothes sit long before there is a bump to see.
It is more important to ask yourself if you still feel comfortable in your clothes, rather than picking a week at random to overhaul your wardrobe.
Five signs it's time to switch
If you are second-guessing yourself, below are some helpful tips.
- Your waistband leaves marks that outlast the trousers. A red groove still visible fifteen minutes after you have changed.
- Your bra band tightens before the cup does. The ribcage expands early in pregnancy to make room for the diaphragm. Most women need a larger band size before they need a larger cup. This is one of the first signs of needing a change in wardrobe.
- You are undoing the top button by lunchtime. The hair-tie trick is a perfectly legitimate stopgap. It stops being a stopgap when you are doing it every day.
- The same trousers fit differently morning and evening. Pregnancy bloating can be dramatic, making the same clothes feel different throughout the day.
- Sitting down is the problem, not standing up. If everything is fine until you sit at a desk or get into a car, your waistband has already run out of room.
What changes, and roughly when
Every pregnancy runs to its own schedule, but you may start to see changes around these dates.
Weeks 4–8: the bra bites back
Long before there is anything to see, your ribcage expands. A soft, non-underwired bra in a larger band size is usually the first maternity purchase and brings quick relief.
Weeks 8–12: the waistband gap
Nothing looks different, but nothing quite fits either. Trousers dig, shirts pull at the buttons, and you may be bloated without showing a bump.
Some women opt for maternity clothes at this point, but for most it is enough to switch to roomier clothes or more elasticated clothes you already own.
Weeks 12–20: the switch
This is where most women make the change, beginning from the bottom half. Proper maternity jeans and trousers remove the pressure across the abdomen entirely. Tops tend to follow a few weeks later, when length becomes the issue.
Weeks 20 and beyond: the full wardrobe
By the second half of pregnancy, most women are in maternity clothes every day. This is also the point at which a maternity dress really earns its place - one good dress covers work, dinner and everything in between with no thinking required.
Why a second pregnancy shows sooner
If this is not your first rodeo, you will probably be in maternity clothes earlier — often from around week eight. Your abdominal and uterine muscles have already been stretched once before and offer less resistance the second time, so the bump appears earlier and rather more suddenly.
Second-time mothers also tend to switch sooner simply because they already know the comfort maternity clothes can bring.
Undercover bump: dressing before you've told work
Between weeks eight and fourteen, many women are in limbo: they haven't told their employer they are pregnant and don't wish to announce it.
A few tips for those in this predicament:
- An open blazer over a skimming top. We love the Lisbeth maternity blazer for this exact purpose.
- A-line and shift shapes. These fall away from the waist rather than sitting on it, so they read as a style choice rather than a change.
- Dark, structured denim in a maternity cut. Under the bump styles sit low on the hip and are essentially undetectable at this stage, while removing the waistband problem completely.
Proper maternity workwear is designed for exactly this problem, and for many is the first category worth buying properly — because it is the one you wear five days a week rather than five times a season.
What to buy first and how little you actually need
When you do buy, buy less than you expect to. Six well-chosen pieces will carry most women through an entire pregnancy without breaking the bank:
- One pair of maternity jeans — over-bump for support, under-bump for a lower profile.
- One pair of maternity leggings for weekends, travel and the days when nothing else appeals.
- Two layering tops in colours you already wear, so they work with everything you own.
- One dress that covers both the office and dinner.
- One generously cut knit or cardigan that will still work at 38 weeks.
Get all these pieces and that can cover most maternity wear for 35 weeks. Very little else in your wardrobe is asked to work that hard.
Buy, rent or pre-loved?
At Isabella Oliver we also offer rental and pre-loved options, for those more conscious of buying new clothes for maternity alone. Here is where each works best:
Frequently asked questions
The takeaway
There is no correct week. Most women switch somewhere between 12 and 20, earlier if it is not their first, and the signal is comfort rather than the calendar. Stretch your own wardrobe for as long as it is genuinely comfortable, then buy a small number of pieces you actually like and wear them into the ground.
Our maternity essentials are designed to do exactly that — cut to your usual size, made from responsibly sourced fabrics, and built to last well beyond the nine months.