JOHN FOSTER / SCIENCE PHOTO LIBRARY JOHN FOSTER / SCIENCE PHOTO LIBRARY
In the five or so days it takes to travel down to the uterus, the fertilized egg changes dramatically. The egg divides and grows attaching itself to the nutrient rich lining of the uterus. It is now called a blastocyst or zygote. Here it will grow from one cell to over two trillion in the next nine months becoming a baby. Pregnancy has begun.
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