Wow, OP ... please look at all of these responses and realize that it is very important to invite your husband's side of the family.
It's just insanity, otherwise. You're starting out the celebration of your child with family drama that doesn't need to be there.
Imagine you have a son... he's an adult, has recently gotten married, and she's now with child. You're excited to hear about an upcoming baby shower, until you see pictures on Facebook. The shower that happened without you

You now hate (or feel hurt by) your daughter in law.
I have a feeling you and your family have an extremely hard time putting yourselves into other people's shoes!!