Child is an affectionate term. Fetus is the correct medical term.
See this definition of child from Dictionary.com. As you can see, a human fetus is a child. Is there something wrong with showing affection to a child?
And why do you feel the need to hide behind medical terms when talking about abortion? Is it because you find it difficult to come to terms with the brutal truth of what is really happening when an abortionist pushes his curette through a mother’s cervix? Does ‘killing a human fetus’ have a better ring to it than ‘killing a prenatal child’? Either way, a living human being is destroyed.