Birth of little one

I would just explain it matter of fact. This is what I tell my 3 year old. Mama and papa are married. We love each other so much and we wanted to have a baby, you - to represent our love. When people are married they have sex. Sometimes when they have sex, the papa ejaculates sperm (looks like a tadpole) and the mama releases an egg (like a chicken) at the same time and those two meet each other and do a mating dance. If they are a correct match - the sperm and the egg, fertilisation occurs and soon a fetus develops in the womb (near my tummy) The fetus becomes a baby- you!