How Long After Sex Does Conception Occur?

From Sex to Conception
Conception can occur while a couple is still curled up in bed after sex. Biggie Productions/Getty Images

There are close to equal numbers of sperm that contain either a male chromosome or a female chromosome. This determines the gender of the baby at the very point of egg fertilization. It will also play a role in the race to reach the egg. While male sperm aren't as hardy, they have a speed advantage. Though slower than their male counterparts, the advantage in longevity goes to female sperm.

But if they survive long enough to reach the fallopian tube, sperm cells can relax and enjoy a safe environment that's conducive to their continued survival. Some actually bind to the fallopian tube itself, as a means of receiving direct nourishment [source:].

When an egg enters the fallopian tube from the other end, it produces a scent that drives the sperm cells crazy. They become very excited and begin a process called capacitation, during which they shed certain proteins and become very excited. Both the shedding of proteins and the boost in mobility aid the sperm cell in its quest to penetrate the egg.

When a sperm cell finally makes contact with the egg, the head of the sperm releases enzymes that help it penetrate the egg's exterior. Once a sperm cell does, the two cells — the sperm and the egg — form a single-celled unit called a zygote, and the change prevents any other sperm cells from getting through [sources:, Suarez].

How long all of this takes can vary. The fastest sperm can get to a fallopian tube is about 30 minutes [source: WebMD.] But capacitation takes an estimated seven hours, so the sperm has to wait at least that long before it can penetrate an egg and begin the process of conception [sources: Reinisch and Beasley, Cleveland Clinic]. Once that happens, it takes about 24 hours for the sperm to finish fertilizing the egg [source: WebMD.]

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