It's not just bloat:
"Like a balloon that’s easier to inflate the second or third
time, so too is the uterus. The Mayo Clinic refers to this as the
“warmed up” effect. Abdominal muscles and ligaments have already been
stretched once making it oh so easy to stretch again."
This is the case with most friends i've seen with their second. No biggie, I say. I just get annoyed with comments it's just bloat. The weekly updates you get from the bump are tailored for first time mom's and don't address mom's who've already gone through a pregnancy.