What's the best explanation of IVF for the child?

Age sensitive. When relating info to kids their developmental age determines their ability to understand. In early childhood, if you are bursting to share this news, short is best."needed drs help to have babies" should suffice. Expect them to return with occl ?S and answer with brief statements.After 7-8 some may understand better, but save elaborate explanation for the nuts & bolts of sex ed in the pre-teen.
IVF kids seem OK... Children conceived by in vitro fertilization (ivf) don't seem more likely to have major health problems than otherwise conceived children, but ivf might have a 'negative impact' on genetics and themselves may have a higher incidence of fertilization difficulties.