If we’re assuming humans being kept well-fed and healthy, in some kind of alien zoo, and encouraged to have sex every day, and babies are immediately taken away to another part of the zoo… then I could see 19 being achievable by the average woman, yes. But that’s an awful lot of assumptions. In real life, some of the women would be underfed, some suffering from various diseases, some recovering from injuries, some dying in childbirth, and they would fight tooth and nail against having their babies taken away. Plus, a significant fraction would lose their sex drive if they figured out that they were being treated as baby factories.