"Her first child is a boy."
Translation:O primeiro filho dela é um menino.
I used this because i will be awkward rather than support the default to masculine that gendered languages tend to force on their speakers. Portuguese seems to use filh@ when talking about the children of parents and criança only when talking about generic children.
To me, though, criança is an excellent solution to not knowing the gender of her first born until the end of the sentence. It's almost better that it's awkward.
One of the answers shown as correct says, "Seu primeiro filho e' um menino." How do you know it's "her" child and not a "his?" In other words, is that duolingo answer acceptable? I had written, "Sua primeiro filho e' um menino," and could understand the "dela" answer as being more correct but didn't understand the "seu" one.