About one week after conception, the fertilized egg, or blastocyst, is ready to implant, or attach to the wall of the uterus.

The blastocyst must become implanted in the wall of the uterus if the pregnancy is going to continue. Implantation occurs in the inner lining of the uterus, called the endometrium. The endometrium is rich in blood vessels and nourishes the fetus as it grows during the 9-month pregnancy.