SO won't tell his parents.

Paige • 25. Baby #1 (LK) is almost 3 years old.
I'm 6 weeks pregnant with my Baby's Daddy. I put SO but we are not together, broke up in June (due to too many arguments/fights) right before I become pregnant with our baby. Now we are happy as can be relationship wise, but note we are still not together. I'm 22, he's 23, both graduated college in May, no big boy/girl jobs yet.
Anyways. I have told my family, they are very supportive. He refuses to tell his family. He still lives at home, and I think he's scared of his family and what they will say/think. I've heard his mom trash talk young single mothers and young families. (She didn't get pregnant until she was married and 40) he hypothetically brought up having a child and she told him he would be cut off, kicked out, and she would disown him as her son... Has anyone else experienced this? What should we do? Should we wait until after the 1st trimester so miscarriage is at a low percentage then? Any advice? Thoughts?