After the egg is released, it moves into the fallopian tube. It stays there for about 24 hours, waiting for a single sperm to fertilize it. All this happens, on average, about 2 weeks before your next period.

How long does it take for fertilization to occur?

Pregnancy doesn't start the day you have sex — it can take up to six days after sex for the sperm and egg to join and form a fertilized egg. Then, it can take three to four days for the fertilized egg to completely implant itself in the lining of the uterus.

Can you tell when fertilization occurs?

Pregnancy begins when a sperm fertilizes an egg. This usually occurs in the 2 weeks following the first day of the most recent menstrual period. In the first few weeks of pregnancy, a woman may have no symptoms. Some can sense that they are pregnant, but most do not suspect it until they miss the next period.