"Oh, I meant I'm sorry you're pregnant. But I'm sorry about that too." Erato was halfway joking- being pregnant did feel pretty special if she didn't think about how uncomfortable and possibly painful her whole body felt for nine months. It was the raising of the child that was the dull part. She pressed a kiss to the top of Melpomene's head and went back to her cake.
It was a little awkward that she'd just been ragging on Ares for fathering too many children, though.