That's a tricky question. Barring developments in cloning, divine intervention, and parthenogenesis, you do need a sperm and an egg to make a baby. But after that it's pretty much up for grabs. Just about anyone who wants to have a baby can have one or get one in any number of ways. Which leads to the question of how we talk to our children about reproduction.
Sex equals reproduction.
Sex therefore is intercourse between heterosexuals who want to make a baby. Or at least that would be how it appears to most unsuspecting elementary school kids who start asking questions about sex, where babies come from, and that sort of thing. I nodded again. Clearly, she had absorbed something of the meaning of reproductive sex, but not much about sexuality. Without overwhelming our children, we need to differentiate between reproduction and sex.