Just my opinion but I don't think you had anything to apologize for. She should have apologized to you for her lack of class/tact. It must be something to come from a world in which people share news with coworkers of their spouse's UNwanted babies. I have sympathy that she would even think that.
Congratulations - you've been blessed. Again.
Let us continue to work for the day when every pregnancy, every new life is cause for rejoicing.
Several years ago, a woman I know of was expecting her 6th child. One day when she was in an elevator with her other kids, a fellow passenger said something to the effect of 'why are you pregnant again?' 'you already have enough kids, don't you?'
She was so upset by it, that she began shaking, and really couldn't respond to the woman. I felt so bad for her. I wasn't there with her when it happened, and I don't have any kids, but if someone would have said anything like that to me, I can assure you that it would have been her shaking, not me.
Can you imagine the gall?