From Slate:

When women can’t have as many children as we want to have, it scrambles our brains. Some of us deal with it through therapy, religion, and tons of personal growth. Others prefer not to address the issue and become bitter harpies who seethe with rage and envy towards more fertile women. I do not recommend this latter path.
I don’t like Usha but I was extremely happy for her when her pregnancy was announced. As I’m happy when anybody’s pregnancy is announced but I’ll confess that the feeling is especially acute when it’s an older mom.
It is not other women’s fault that we have been blighted in the reproductive area. Their easy, healthy pregnancies don’t take anything from us. The only right thing to do is to be sincerely happy for them.
No matter the hardship that has touched your life, you can always decide not to be a shit, is what I’m saying.