What is implantation and when does it happen?
Implantation occurs when the fertilized egg attaches itself to the wall of the uterus. On average, it takes place 9 days after ovulation (ranging normally between 6-12 days) for the blastocyst, the developing embryo to reach the uterus and attach to the uterine lining. Fertilization is when the sperm joins with the egg, and implantation is usually considered the beginning of pregnancy. At this early stage of prenatal development, the embryo is called a blastocyst.
What happens with implantation and the pregnancy hormone hCG?
As soon as the blastocyst implants, it emits the pregnancy hormone hCG, or Human Chorionic Gonadotropin, into the mother's bloodstream.
The hCG can first be detected in the blood about 3-4 days after implantation, and this is when a positive blood test can confirm a pregnancy. The urine pregnancy test becomes positive 1-2 days later. That is often several days before you expect your next period or around the time of a missed menstrual bleeding.
This implantation calculator will give you the days likely for implantation. It will also let you know when you can expect a pregnancy test to show positive.