05/28/2013 03:36 pm ET Updated Jul 28, 2013

What Gender Doesn't Have to Do With Making Babies

When I sat down to write What Makes a Baby, I didn't think gender would be the most controversial part. I thought that if anyone had a problem with the book it would be because I don't put a married heterosexual couple in the middle of the story.

I should have known.

One of the happy side effects of how and where I introduce gender in the book is that I don't represent one kind of family as normal and every other one as a deviation. The book does, however, favor a family where a child is loved and where their presence is enriching. But the value of a family is not measured by the gender, orientation, race, class, or bodies of the people in it.

It's a simple story, which is good, because it's meant for 4-year-olds. There are plenty of more complicated lessons about families to come, of course. But we wanted to start with real uncomplicated truths. This is actually much harder than you might think.

The way we chose to accomplish it was by keeping the bodies at the beginning of the book gender ambiguous. As the story progresses and we move closer to the birth you see all sorts of people who can be read as gendered in one way or another. People with personalities and cool T-shirts and awesome glasses, and freckles.

But we start with bodies. And we explain that some bodies have eggs and some don't. Some bodies have sperm and some don't. Some bodies have a uterus and some don't. We don't gender the bodies and we don't gender their parts.

So far, this has been the most challenging part of the book to explain to grown-ups (though kids don't seem to have the same difficulty).

As a sex educator it is my job to think about what information I introduce, when I introduce it, and how it gets introduced. What Makes A Baby was not designed to be the most comprehensive guide to where babies come from. It is a first book about reproduction. And it offers the simplest possible explanation of what you need to make a baby.

People have asked: if I want to keep it simple, why don't I just say that bodies with eggs are women and that bodies with sperm are men?

My simple answer is, because it isn't true, and it isn't simple.

Women are more than bodies with eggs, men are more than bodies with sperm, and (here's the real whopper) not all people who check the "female" gender box have eggs and not all people who check the "male" box have sperm.

That is simple truth. It ain't complicated, but if it is hard to understand that's because it challenges our weird grown-up mishmash of ideas about gender, sex, reproduction, and rearing.

That mishmash may masquerade as pure and simple truth, but the ongoing debates about how and where to draw lines around such 'natural facts' as biological sex (witness recent controversies about "gender testing" in sport) are proof that this mishmash is so complicated it is the stuff of endless scientific, political, and social debate.

That is hardly solid material out of which to make the foundation of a comprehensive, and eventually complicated, understanding of what makes a baby.

If you think that these distinctions only matter for those of us who are on the margins of what is considered normative gender or sexual identities, you're absolutely wrong. Stay tuned next week for examples of how the facts of life, as we're currently taught them don't add up to a full life for any of us.