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The federal government's National Library of Medicine -- a part of the National Institutes of Health -- maintains a Web page entitled, "Fetal Health and Development." It links to a publication of The American Academy of Family Physicians, which is entitled, "Your Baby's Development: The First Trimester."

I utterly hate it when scientific concepts are so oversimplified for the layperson that they actually become incorrect. Pregnancy is the state of the woman's body after a blastocyst implants. The events that are necessary for her to become pregnant may have started with the union of sperm and egg, but unless a blastocyst implants, she won't become pregnant. And I'm sure that the whole statement about "After conception, your baby..." is a drastic oversimplification which is not intended to convey the idea that physicians universally consider a zygote and a newborn as being identical save for size. There is a real challenge in writing for laypeople and maintaining scientific accuracy.

For a more accurate and scientific view, try reading Reproductive Biomedicine Online. There is a common theme to those scientific articles: those who work in the area of reproductive medicine do not consider a pregnancy successfully established until they can detect the fetal heartbeat at gestational weeks 6 to 8. (I'm not sure how they count gestational weeks in the context of in vitro fertilization, but in normal pregnancy, that would be 4 to 6 weeks post-conception.) The fetal heart develops at the same time as the nervous system; many people consider initiation of heart beat as the beginning of a human being's life.