Firstly congratulations on your pgcy. I am currently expecting number 6, so you could imagine the sort of things that somepeople are going to say to us IRL. It would be nice for those we care about be happy for us, but you need to remember one thing. Once that bub arrives everyone changes, and they may even feel abit guilty for being so negative. What I can gather this is your 1st but your DH's 3rd, what is wrong with your MIL. I would hope your DH doesnt listen to his mother and get the snip. Did you and your DH have the understanding that kids would be on the cards one day? If so then he shouldnt be worried about what anyone says. This is your child together and should be celebrated.
Congratulations again hun, and enjoy this precious gift both you and your DH have been given. hugs