Quote from Phoebe in The One Where Chandler Takes a Bath
Phoebe: Are you going to find out the sex of the baby?
Ross: No, no. We talked about it and we don't wanna know. All we care about is it's happy and healthy.
Rachel: Yep, happy and healthy. And cute.
Ross: With an aptitude for science.
Phoebe: Are you two talking about the same baby?