So That's How I Was Born!, 1983. Little Simon.

This book is a resource for parents to help them to articulate and answer questions about sex frequently raised by young children. Very importantly, the book attempts to capture the many feelings that arise when children first confront the facts of life--feelings ranging from curiosity and excitement to disbelief and anxiety. Children will learn that their own thoughts and feelings about sex are not unusual thereby making it easier for them to ask questions of their parents. Illustrated by Susan Perl.

This book is available through or your local bookstore.