A tiny ball consisting of several hundred cells are multiplying by the minute.
Once these cells take up residence in your uterus, the part of it that will develop into the placenta starts producing the pregnancy hormone HCG.
HCG tells your ovaries to stop releasing eggs, and is the hormone that turns a pregnancy test positive.
You probably don’t know you’re pregnant yet, but you may notice a little spotting by the end of this week. This may be caused by the egg burrowing into the uterine lining, but no one knows for sure. The spotting is very light and only a minority of pregnant women experience it at all.
It would be ideal to take a daily multivitamin that contains at least 400 micrograms of folic acid to reduce risk of birth defects.