Just a short list of 3 items I use now on a daily base and I think worth to buy. Probably not surprising, but 2 of the items I consider as my best investments during pregnancy are from the category underwear...
1st trimester: a good maternity-bra
While I was able to wear my own bra's during the first 10-11 weeks, suddenly around week 12 I needed to invest in a larger size bra.
I choose to get a very good quality and therefore not cheap bra which I can wear and wash on a daily base. It is a long-term investment because I will be able to wear it through both the 2nd and 3rd trimesters. (It is completely individual how much 'everything' grows during your pregnancy, so you might need to 'upsize' more than once in the nine months)
Mine is wireless and has an extra inner layer in the cups which is stretchy and easily can grow a size or 2 with you. When buying I choose a size larger cups than I needed at that time and I'm happy to report that this bra still fits!
2nd trimester: maternity support pillow
From the 20'th week on I sleep with my diy maternity support pillow and I can't imagine the nights without it! Normally I sleep on my belly, and with the pregnancy it is impossible after a while. Very annoying! Now I fall asleep on my left side hugging my support pillow!
3rd trimester: bump-supporting shapewear
Since I work full-time as a nurse and I have to stand, walk around most of the time I noticed that my bump tends to feel heavier after a day at work.
Past week I decided it was time to buy a bump-supporting brief to support both my belly and back. There is enough choice from different maternity brands, but since normal shapewear was on sale in our local HEMA (a Dutch company) I decided to buy one of those for my last 11 pregnant weeks.
I choose a brief (for work) with a light support, and 2 sizes larger than I'd normally buy. Normally I wear size S clothing items, but for underwear size up to M anyway. The shapewear/supporting I've got now is size XL.
The price was just a bit more than 6 euro's and it works great! The 'supporting' upper part stretches comfortably over the lower part of my bump and while it doesn't squeeze, it really makes the difference at the end of the day!
Note: to keep my abdominal muscles active, I only wear it when at work and since today during running.