How can fertility be controlled by contraceptives?

Answer 1

Fertility is the capacity of an organism to produce offspring. Contraceptives control fertility in a variety of different ways.

Behavioral contraceptives include abstinence. Abstinence is the practice of not having any sexual intercourse, which controls fertility by eradicating the possibility of pregnancy. Practicing abstinence means that that the male and female gametes (the sperm and the egg) will never meet. Since a sperm and egg must meet in order to create an embryo (which will eventually become a baby), this form of contraception decreases fertility.

Chemical contraceptives include the pill, the Birth Control patch, the birth control implant, the morning after pill, and the shot (in humans). All of these are meant to be used by women. These chemical contraceptives change the female hormonal balance so that her body 'thinks' that it is already pregnant, even though it is not. This decreases fertility because the body does not ovulate (release viable eggs). Even when a sperm enters into the female reproductive tract, it will not find any eggs to fertilize.

Barrier contraceptives include the condom, the female condom, and the diaphragm (in humans). These contraceptive methods involve creating an actual physical barrier between the male sperm and the female egg, preventing fertilization and decreasing fertility. Barrier contraceptives can be used by both men and women.

Finally, there are more permanent methods of fertility control, such as vasectomies for men, and sterilization for women. In both cases, the body is surgically altered so that the viable gametes created cannot travel to the part of the body that allows contact to the gametes of the opposite sex. Dogs and other pets are often neutered and spayed, with effectively the same result. In this case, the animals' bodies are surgically altered so that the area that produces gametes is removed entirely. Surgical methods of contraception often decreases fertility to zero.

This answer is not meant to be a comprehensive explanation of human birth control methods, nor is it meant as medical advice. The effectiveness, morality, or availability of various methods are not in any way referenced in this answer: please consult other sources for such information.

Please consult your physician before considering any of these methods for your own use.

In the 'related links' section, you can find the Planned Parenthood site on contraceptives, which should provide additional scientific information on all of the methods mentioned in the answer.