I've recently been hearing thoughts from folks about not blanketing mares so the foal wouldn't get tangled in the leg straps and I have yet to hear from someone who actually has had a problem. So, not sure where this came from?
Anyhoo, I blanket my mares or sheet them as needed and have never had a problem. When the foal is brand new, I do have a couple of nice belly band blankets and I can take the leg straps off and I pin the sides up, right at the hip. That way the foal doesn't get confused or frustrated when trying to find 'the milk bar'. Before I started pinning the sides up a little, I never actually had a foal that couldn't find where to nurse, but I did see a few get pretty flustered at the blanket sides, LOL!
Under normal circumstances I also try to breed so the mares foal out in March or April, which is pretty warm down here (90 something today), so they don't usually need blanketing or sheeting this time of year. This year though, all 3 foaled in early to mid-Feb because I bred futurity babies.