""Mrs. Barber, medically impossible though it seems at your age, there's no doubt about it: you're pregnant."" Carla was well into her sixties when she went to her doctor complaining of nausea, exhaustion, and occasional cramps. After a thorough examination the doctor sent her to the hospital for a battery of tests, and finally confronted her with the results. ""Mrs. Barber, medically impossible though it seems at your age, there's no doubt about it: you're pregnant."" ""Impossible,"" she cried,…