The general formula is:
Jeans + vest+ tripey top + big cardigan
This sometimes varies to:
Leggings (or tights, but I generally find maternity tights to be useless) + vest (if there's room) + stripey dress + big cardigan.
Then add in a scarf (mostly to cover up my terrible pregnancy skin on my back, chest and behind my ears), a tote bag, either my desert boots or a pair of converse (or faux DM's for work) and that's it really. Occasionally I'll wear a pin badge too but they're generally reserved for my denim jackets, which it has been too cold to wear lately. Oh, yeah, and a coat. I've been wearing the same (non-maternity) coat to death all of this winter and I can't even do it up anymore.... But said scarf tends to cover the chilly middle. I'm pretty pleased that I managed the winter without buying a coat; I know that this will be my last pregnancy so I know I won't need another - plus I was annoyed at myself for charity-shop-bagging the coat I used last time around. It wasn't a maternity coat, but I could do it up right 'til the end. It just got a but musty and bobbly so I gave it up during a decluttering phase.
I think there's something about being up the duff that lends itself well to execution of the capsule wardrobe concept; largely that no one really wants to shell out for tons of new clothes that you're not going to wear for very long, so it forces you to pick carefully and make combinations from the few pieces you do have. I say 'few' but I recently added up all the things I've been wearing during this pregnancy and it came to 25 things. Including vests and bras, but not including pants, socks and pyjamas. Or shoes. I've probably only worn about 5 different pairs of shoes, max. I'd say that less than half of those things have been bought during this pregnancy - or indeed for pregnancy at all as I tend to wear loose clothes anyway - and if they have then they were cheap. The most I've paid for anything is £25 for a decent pair of black maternity jeans which have served me incredibly well.
Anywho... I wanted to just share a handful of my favourite clothing combinations from this pregnancy as I've been pretty happy with my maternity 'style' this time round. And I haven't got an awful growth on my face this time either so I feel a bit more confident about my appearance in general. I have to dress to cover up my skin (and reluctance to wear a bra because I find them too uncomfortable - even sporty, under-wireless ones.)
Here is an outfit I wore yesterday - my first 'proper' day of maternity leave (i.e. a Monday). It fits into formula #1 of the two I mentioned pretty squarely.
My blazer-y cardigan was an impulse sale-buy a few weeks ago from Miss Selfridge at my nearest Outfit store. I only paid £9 for it as I had a gift voucher from Christmas but even its sale price was more than I'd pay for most things. I think it was £29 reduced from close to £40 - so not a huge sale bargain and if it weren't for the voucher I'd have left it on the rail. Fast-fashion has made me really reluctant to spend money on clothes, which is awful because I know the conditions in which they're made, but it seems like unless you pay significantly/prohibitively more (like £100 more) then buying things not made in those conditions is unavoidable.
The oversized pink scarf was from H&M a few months ago, around £12. It could double up as a blanket if you needed one. In fact I think I used it as one when I went to see La La Land last month.
The top and jeans were both from New Look. The top was full price (two for £12) and the jeans were a bit of a steal at just £7 in the sale. I was fully prepared to hate them when they arrived, but I've been living in them.
The long vest underneath is a plain, adjustable spaghetti number from H&M. I have about four of the same vest as they're long enough to compensate for any riding up of your top and tight enough to give me (a very modest-busted lady) a little bit of support. And to reduce see-through-ness, of course.