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Fertilization refers to the fusion of the egg and sperm, and typically occurs in the ampulla of the fallopian tube. The result of fertilization is defined as a zygote cell, a fertilized egg that initiates prenatal development.

Sperm is attracted to the progesterone in the fallopian tubes, which later binds to the a receptor on the sperm membrane. Once the progesterone binds to the receptor, sperm motility increases, guiding the sperm cell to the oocyte.

While the most common form of fertilization is that which occurs in the female body, other methods have risen to the forefront in recent years, such as in vitro fertilization.

Fertilization and male fertility

Males experiencing fertility issues will encounter difficulty fertilizing their partner’s egg. Poor sperm motility, the ability of sperm to “swim,” or reduced sperm count may significantly reduce the chance of fertilization. Poor sperm morphology — the number of sperm that have the proper size and shape — may also reduce the ability of a sperm to fertilize an egg.

Couples experiencing difficulty conceiving as a result of male infertility could turn to assisted reproductive technology (ART) procedures, including in vitro fertilization and artificial insemination. In vitro fertilization is a procedure in which the egg is combined with sperm outside the body, in a lab. Artificial insemination, by contrast, is a process in which the sperm is injected directly into the patient’s uterus or cervix, increasing the chances of fertilization.

History of fertilization

Fertilization has been studied since the 16th century. It was only in 1784, however, that Italian biologist and physiologist Lazzaro Spallazani established the relationship between male sperm and a female’s eggs in frogs. In 1824, therian Karl Ernst Ritter von Baer followed up on Spallazani’s work, observing a mammalian egg for the first time. Later, in 1876, German embryologist Oscar Hertwig made a significant contribution of his own, describing the fusion of the sperm and eggs in sea urchins.
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