It amuses *me* that you failed to answer the question.
What "natural process" brings a test-tube-baby to term? Seems to me there'd be some artificiality involved. But tell us... what's the "natural" process?
Drum roll.....
Pregnancy.
Unless you think a Doctor implanting an embryo in the uterine wall is a supernatural process you are once again digging ever deeper. Dig away Sir Techno!