Why not Pictish - I was quite clear to DH I expected him to act as gatekeeper to my parents who are "hard work" and stress me out after I had DC1 (by DC2 I knew I was having a csection so I had time to plan and manage them myself).
After you've just given birth you are vunerable and need to be looked after, a big part of that IMO is making sure anyone who will stress the new mother is kept away from them (or managed in a way to avoid the stress being passed on). Although in this case, not only was the MIL causing problems and not being managed by the OP's DH, he was getting wound up and rather than keeping that to himself, he took it out on his DW who'd just had a baby.
The DH is a problem, he should learn to manage his reactions to his mother's flapping as well as managing her flapping.
I really hope if/when I'm a MIL I am the sort (like my MIL) who is a help, not someone who has to be "managed". (Same if DD has DCs)
Some people are lucky, they have parents and parents-in-law who are helpful people, some of us have ones who aren't just not a help, but actively a problem. Mind you, at least it's only my parents who are the problem, my PIL are fabulous people who are either in the "not a problem" camp or the "really helpful and supportive" camp - so they did get to see DC2 a full 24 hours before my parents, because their visit didn't require effort or stress.