Why is the news about pregnancy bittersweet for john proctor?

The news of Elizabeth Proctor's pregnancy is certainly not bittersweet for John Proctor. He is genuinely happy about it. However, he is very well aware that in Salem, having a child can be problematic. Elizabeth will have to go through a lot of pain, and there has already been a case where a woman (Martha Corey) died in labor. John is well aware of this, and the thought of it worries him. However, it does not take away his joy at the news of becoming a father.