What is implantation and when does it happen?
Fertilization takes place before implantation and occurs when the sperm joins with the egg. Implantation occurs when the fertilized egg (the blastocyst/embryo) attaches itself to the wall of the uterus. On average, implantation takes place 9 days after ovulation/fertilization. It normally takes between 6-12 days for the developing embryo to reach the uterus and attach to the uterine lining. Implantation is usually considered the beginning of pregnancy. At this early stage of prenatal development, the embryo is often called a blastocyst.
Read about typical implantation signs and symptoms
What happens with the pregnancy hormone hCG during implantation?
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 period.
This implantation calculator will give you the days you may likely experience implantation. It will also let you know when you can expect a pregnancy test to be positive.