Good on you for sticking to your guns and eating carefully. I copped that alot with my first pregnancy. I explained it a few times and then gave up and just said " I want a healthy baby" Very hard for people to say much to that. Keep up the good work. This time around people arent saying anything as they know how strongly I feel about it. My Mum is fantastic! For my first she didnt know about any of it but was extremely supportive and this time around is aware so is even more supportive and careful with what food she offers me. She even defends my choices to others. Hubby is super cautious and even reminds me when I get a little slack. Maybe you could have your hubby have a word to his mum and sister to leave you be.
As others have said this is just the beginning of peoples comments and judgements on what you do with your child. Stay strong to what choices you make and never let anyone make you doubt your choice.