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Those qualities are surely as essential in this difficult field as are flasks, hormones and microscopes. Though man has wondered about human reproduction since the dawn of history, it remains, in many respects, as mysterious—some would even say as mystical—as ever. At birth, the infant human female is endowed with as many as a million egg cells, many more than she will ever need during her 30 or so child-bearing years. Starting at puberty, eggs are released, usually one at a time, about midway in the menstrual cycle. The process is intricate and marvelous. Stimulated by hormones, part of the body's chemical signaling system, a ripe egg is expelled from its grapelike encasement, or follicle, in the ovary; in any month, either of the female's two ovaries may contribute an ovum. Then the egg enters the nearby fallopian tube. If coitus has taken place, the egg will shortly run into a swarm of tailed sperm that have managed, like salmon battling upstream, to fight their way into this passageway. In a dramatic headlong plunge, a single sperm will penetrate the waiting ovum's outer layer, its 23 chromosomes joining the egg's 23. That produces the full complement of 46 chromosomes, which contain all the genetic instructions necessary to produce a complete human being.
The fertilized egg continues its journey, dividing as it moves through the tube. Finally, after several days, it will have become a blastocyst, a hollow, ball-shaped cluster of fewer than 100 cells. By now, it will have reached the uterus. There the blastocyst embeds itself in the uterine wall, where it begins drawing nourishment from the mother and starts the miracle of differentiation: the rapid transformation of cells into tissue that soon becomes recognizable as heart, brain, muscle, kidneys and all the other components of a living, self-sufficient being.
Yet the egg's journey is precarious. Unless the proper hor mones are present in appropriate concentrations, setting the stage for ovulation and fertilization, this intricate chain of events will not be initiated. The egg will not burst from the ovary, the cervical mucus will be too sticky for the entry of sufficient sperm into the uterus, and the lining of the uterus will not prepare to receive the fertilized egg. Indeed, hormonal disorders at any point in the sequence make it so fraught with peril for eggs and sperm that perhaps a third of all potential pregnancies end at the time of implantation. As Dr. Albert Decker of the New York Fertility Research Foundation puts it, "Pregnancy is not simple. Women do not get pregnant at the drop of a hat."
In Lesley Brown's case, the difficulties were not hormonal but tubal. In recent years surgeons have managed to repair many tubes with precise microsurgery. But for Mrs. Brown that did not appear possible. The door to pregnancy seemed to be tightly shut until she was referred to Steptoe, who with Edwards had probably made more attempts than any other researchers to get around such blockages by in-vitro fertilization and implanting techniques.