They did not test unborn babies. They tested human bood and gut cells in test tubes or petri dishes - "in vitro" testing . You may be thinking of "in vitro" fertilization used by couples who cannot conceive a child because of the man's low sperm count or the woman's inability to produce healthy eggs, etc. The woman's egg is fertilized by the man's sperm "in vitro" - in a petri dish - then transplanted into the woman's uterus for gestation and eventual birth.