What the term ‘window of conception’ means? The lifespan of a mature egg is just 12-24 hours. It means that for conception to occur the sperm has to penetrate the egg within this period. On the other hand, the tiny and motile sperms can live for 3-5 days in the vaginal canal and the uterus. Also, they have the upper hand in terms of numbers.
At every ejaculation, approximately 250 million sperms enter the vagina along with the seminal fluid. While more than half of these will seep out, many others will die or get lost as they travel up through the cervix and into the uterus. However, about 200 of the sperms will make it close to the site of the egg. It only takes one sperm to fertilize it. How do you think, are the chances to conceive in such a case high? Yes, they definitely are!
Although several sperms will attach themselves to the egg and try to penetrate its outer wall, only one will usually manage to burrow through this layer and fertilize the nucleus. Once this is accomplished, the outer layer of the egg quickly thickens to keep other sperms out. Take the lifespan of the sperm and that of the egg, and you will have the window of about 6 days for conception.