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Biology LibreTexts

22.11: Contraception

  • Page ID
    22622
  • Family Planning Pioneer

    Her name was Marie Stopes, and she was a British author and paleobotanist who lived from 1880 to 1958. She is pictured here in her lab next to her microscope. Stopes made significant contributions to science and was the first woman on the faculty of the University of Manchester in England. Her primary claim to fame was her work as a family planning pioneer.

    Marie Stopes
    Figure \(\PageIndex{1}\): Marie Stopes in her laboratory in 1904. (Public domain; author unknown via wikimedia.org).

    Along with her husband, Stopes founded the first birth control clinic in Britain. She also edited a newsletter called Birth Control News, which gave explicit practical advice on how to avoid unwanted pregnancies. In 1918, she published a sex manual titled Married Love. The book was controversial and influential, bringing the subject of contraception into wide public discourse for the first time.

    What is Contraception?

    About a century after Married Love, more than half of all fertile married couples worldwide use some form of contraception. Contraception, also known as birth control, is any method or device used to prevent pregnancy. Birth control methods have been used for centuries, but safe and effective methods only became available in the 20th century, in part because of the work of people like Marie Stopes.

    Effectivenessofcontraceptives.
    Figure \(\PageIndex{2}\): This figure compares different contraceptive methods and devices in terms of their effectiveness at preventing pregnancies with typical use. (Public Domain; Center for Disease Control and Prevention via wikimedia.org).

    Many different birth control methods are currently available, but they differ considerably in their effectiveness at preventing pregnancy. The effectiveness of contraception is generally expressed as the failure rate, which is the percentage of women who become pregnant using a given method during the first year of use. Virtually no one uses any method of birth control perfectly, so the failure rate with typical use is almost always higher — and often much higher — than the failure rate with perfect use. For example, with the perfect use, a birth control method might have a failure rate of just one percent, whereas, with typical use, the failure rate might be 25 percent. For comparison, there is an average one-year pregnancy rate of 85 percent if no contraception is used.

    All methods of birth control have potential adverse effects, but their health risks are less than the health risks associated with pregnancy. Using contraception to space the children in a family is also good for the children’s health and development, as well as for the health of the mother.

    Types of Contraception and Their Effectiveness

    Types of birth control methods include barrier methods, hormonal methods, intrauterine devices, behavioral methods, and sterilization. With the exception of sterilization, all of these methods are reversible. Examples of each type of birth control method and their failure rates with typical use are described below. Much of the information is also summarized in Figure \(\PageIndex{2}\).

    Barrier Methods

    Barrier methods are devices that are used to physically block sperm from entering the uterus. They include condoms and diaphragms.

    Condoms

    Condoms are the most commonly used method of birth control globally. There are condoms for females and males, but male condoms are more widely used, less expensive, and more readily available. Both types of condoms are pictured below. A male condom is placed on a man’s erect penis, and a female condom is placed inside a woman’s vagina (Figure \(\PageIndex{3}\)).

    Dual Condoms.png
    Figure \(\PageIndex{3}\): (left) Rolled up male condom. (right) An unrolled female condom (Public Domain; Tomhannen and Anka Grzywacz, respectively, via wikimedia.org)

    Whichever type of condom is used, it must be put in place before sexual intercourse occurs. Condoms work by physically blocking ejaculated sperm from entering the vagina of the sexual partner. With typical use, male condoms have an 18 percent failure rate, and female condoms have a 21 percent failure rate. Unlike virtually all other birth control methods, condoms also help prevent the spread of sexually transmitted infections (STIs), in addition to helping to prevent pregnancy.

    Diaphragms

    Diaphragms, like the one in Figure \(\PageIndex{4}\), ideally prevent sperm from passing through the cervical canal and into the uterus. A diaphragm is inserted vaginally before sexual intercourse occurs and must be placed over the cervix to be effective. It is usually recommended that a diaphragm be covered with spermicide before insertion for extra protection. It is also recommended that the diaphragm be left in place for at least six hours after intercourse. The failure rate of diaphragms with typical use is about 12 percent, which is about half that of condoms. However, diaphragms do not help prevent the spread of STIs, and their use is also associated with an increased frequency of urinary tract infections in females.

    Contraceptive diaphragm
    Figure \(\PageIndex{4}\): A diaphragm is pictured here beside a U.S. quarter coin for size comparison. The diaphragm should fit snugly over the cervix so it blocks sperm from entering the cervical canal. (Public domain; Axefan2 via wikimedia.org).

    Hormonal Methods

    Hormonal contraception is the administration of hormones to prevent ovulation. Hormones can be taken orally in birth control pills, implanted under the skin, injected into a muscle, or received transdermally from a skin patch. Hormonal methods are currently available only for women, although hormonal contraceptives for men are being tested in clinical trials.

    Birth control pills are the most common form of hormonal contraception. There are two types of pills: the combined pill (which contains both estrogen and progesterone) and the progesterone-only pill. Both types of pills inhibit ovulation and thicken cervical mucus. The failure rate of birth control pills is only about one percent or less if used perfectly. However, the failure rate rises to about ten percent with typical use, because women do not always remember to take the pill at the same time every day. The combined pill is associated with a slightly increased risk of blood clots, but a reduced risk of ovarian and endometrial cancers. The progesterone-only pill does not increase the risk of blood clots, but it may cause irregular menstrual periods. It may take a few weeks or even months for fertility to return to normal after long-term use of birth control pills.

    Intrauterine Devices

    An intrauterine device (IUD) is a T-shaped or coiled plastic structure that is inserted into the uterus via the vagina and cervix that contains either copper or a hormone (Figure \(\PageIndex{6}\)). You can see an IUD in the uterus in the drawing of the female reproductive system below. An IUD is inserted by a physician and may be left in place for months or even years. A physician also must remove an IUD, using the strings attached to the device. The copper in copper IUDs prevents pregnancy by interfering with the movement of sperm so they cannot reach and fertilize an egg. The copper may also prevent implantation in the unlikely circumstance of a sperm managing to reach and fertilize an egg. The hormones in hormonal IUDs prevent pregnancy by thickening cervical mucus and trapping sperm. The hormones may also interfere with ovulation, so there is no egg to fertilize. For both types of IUDs, the failure rates are less than one percent, and failure rates with typical use are virtually the same as failure rates with perfect use. Their effectiveness is one reason that IUDs are among the most widely used forms of reversible contraception. Once removed, even after long-term use, fertility returns to normal immediately. On the other hand, IUDs do have a risk of complications, including increased menstrual bleeding and more painful menstrual cramps. IUDs are also occasionally expelled from the uterus, and there is a slight risk of perforation of the uterus by the IUD.

    Blausen 0585 IUD
    Figure \(\PageIndex{6}\): An IUD is placed inside the uterus by a doctor and left in place to provide long-acting but reversible contraception. (CC BY 3.0; Blausen.com staff (2014); WikiJournal of Medicine).

    Behavioral Methods

    The least effective methods of contraception are behavioral methods. They involve regulating the timing or method of intercourse to prevent the introduction of sperm into the female reproductive tract, either altogether or when an egg may be present. Behavioral methods include fertility awareness methods and withdrawal. Abstinence from sexual activity, or at least from vaginal intercourse, is sometimes considered a behavioral method, as well — but it is unlikely to be practiced consistently enough by most people to prevent pregnancy. Even teens who receive abstinence-only sex education do not have reduced rates of pregnancy. Abstinence is also ineffective in cases of nonconsensual sex.

    Fertility Awareness Methods

    Fertility awareness methods involve estimating the most fertile days of the menstrual cycle and then avoiding unprotected vaginal intercourse on those days. The most fertile days are generally a few days before ovulation occurs, the day of ovulation, and another day or two after that. Unless unprotected sex occurs on those days, pregnancy is unlikely. Techniques for estimating the most fertile days include monitoring and detecting minor changes in basal body temperature or cervical secretions. This requires daily motivation and diligence, so it is not surprising that typical-use failure rates of these methods are at least 20 to 25 percent, and for some individuals may be as high as using no contraception at all (85 percent).

    1048px-MenstrualCycle2_en.svg.png
    Figure \(\PageIndex{7}\): A woman’s basal body temperature rises slightly when ovulation occurs and stays slightly elevated until the start of the next menstrual period. (CC BY-SA 3.0; Isometrik via wikimedia.com).

    Basal body temperature is the lowest body temperature when the body is at rest (usually during sleep). It is most often estimated by a temperature measurement taken immediately upon awakening in the morning and before any physical activity has occurred. Basal body temperature normally rises after ovulation occurs, as shown in the graph below. The increase in temperature is small but consistent and may be used to determine when ovulation occurs, around which time unprotected intercourse should be avoided to prevent pregnancy. However, basal body temperature only shows when ovulation has already occurred, and it cannot predict in advance when ovulation will occur. Sperm can live for up to a week in the female reproductive tract, so determining the occurrence of ovulation only after the fact is a major drawback of this method.

    Monitoring cervical mucus has the potential for being more effective than monitoring basal body temperature because it can predict ovulation ahead of time. As ovulation approaches, cervical secretions usually increase in the amount and become thinner (which helps sperm swim through the cervical canal). By recognizing the changing characteristics of cervical mucus, a woman may be able to predict when she will ovulate. From this information, she can determine when she should avoid unprotected sex to prevent pregnancy.

    Withdrawal

    Withdrawal (also called coitus interruptus) is the practice of withdrawing the penis from the vagina before ejaculation occurs. The main risk of the withdrawal method is that the man may not perform the maneuver correctly or in a timely manner. The fluid typically released from the penis before ejaculation occurs may also contain some sperm. In addition, if sperms are ejaculated just outside of the vagina, there is a chance they will be able to enter the vagina and travel through the female reproductive tract to fertilize an egg. For all these reasons, the withdrawal method has a relatively high failure rate of about 22 percent with typical use.

    Sterilization

    Vasectomy
    Figure \(\PageIndex{8}\): The red line (F) shows where each vas deferens (K) is clamped or cut in a vasectomy. The other structures are A. penis, B. urethra, C. scrotum, D. testis, E. epididymis, G. prostate, H. seminal vesicle, I. bladder, J. pubic bone. (CC0; Rhcastilhos via wikimedia.org).

    The most effective contraceptive method is sterilization. In both sexes, sterilization generally involves surgical procedures that are considered irreversible. Additional surgery may be able to reverse a sterilization procedure, but there are no guarantees. Male sterilization is generally less invasive and less risky than female sterilization.

    Male Sterilization

    Male sterilization is usually achieved with a vasectomy. In this surgery, the vas deferens from each testis is clamped, cut, or otherwise sealed (Figure \(\PageIndex{8}\)). This prevents sperm from traveling from the epididymis to the ejaculatory ducts and being ejaculated from the penis. The same amount of semen will still be ejaculated, but it will not contain any sperm, making fertilization impossible. After a vasectomy, the testes continue to produce sperm, but the sperms are reabsorbed. It usually takes several months after a vasectomy for all remaining sperm to be ejaculated or reabsorbed. In the meantime, another method of birth control should be used.

    Female Sterilization

    The procedure undertaken for female sterilization is usually tubal ligation. The Fallopian tubes may be tied or cut in a surgical procedure, which permanently blocks the tubes. Alternatively, tiny metal implants may be inserted into the Fallopian tubes in a nonsurgical procedure. Over time, scar tissue grows around the implants and permanently blocks the tubes. Either method stops eggs from traveling from the ovaries through the Fallopian tubes, where fertilization usually takes place.

    Emergency Contraception

    Emergency contraception is any form of contraception that is used after unprotected vaginal intercourse. One method is the so-called “morning-after” pill. This is essentially a high-dose birth control pill that helps prevent pregnancy by temporarily preventing ovulation. It works only if ovulation has not already occurred, and when taken within five days after unprotected sex. The sooner the pill is taken, the more likely it is to work. Another method of emergency contraception is the IUD. An IUD that is inserted up to five days after unprotected sex can prevent nearly 100 percent of pregnancies. It keeps sperm from reaching and fertilizing an egg or inhibits implantation if an egg has already been fertilized. The IUD can then be left in place to prevent future pregnancies.

    Summary

    • More than half of all fertile couples worldwide use contraception (birth control), which is any method or device used to prevent pregnancy. Different methods of contraception vary in their effectiveness, typically expressed as the failure rate, or the percentage of women who become pregnant using a given method during the first year of use. For most methods, the failure rate with typical use is much higher than the failure rate with perfect use.
    • Types of birth control methods include barrier methods, hormonal methods, intrauterine devices, behavioral methods, and sterilization. Except for sterilization, all of the methods are reversible. All of the methods have health risks, but they are less than the risks of pregnancy.
    • Barrier methods are devices that block sperm from entering the uterus. They include condoms and diaphragms. Of all birth control methods, only condoms can also prevent the spread of sexually transmitted infections.
    • Hormonal methods involve the administration of hormones to prevent ovulation. Hormones can be administered in various ways, such as in an injection, through a skin patch, or — most commonly — in birth control pills. There are two types of birth control pills: those that contain estrogen and progesterone, and those that contain only progesterone. Both types are equally effective, but they have different potential side effects.
    • An intrauterine device (IUD) is a small T-shaped plastic structure containing copper or a hormone that is inserted into the uterus by a physician and left in place for months or even years. It is highly effective even with typical use, but it does have some risks, such as increased menstrual bleeding and, rarely, perforation of the uterus.
    • Behavioral methods involve regulating the timing or method of intercourse to prevent the introduction of sperm into the female reproductive tract, either altogether or when an egg may be present. In fertility awareness methods, unprotected intercourse is avoided during the most fertile days of the cycle, as estimated by basal body temperature or the characteristics of cervical mucus. In withdrawal (coitus interruptus), the penis is withdrawn from the vagina before ejaculation occurs. Behavioral methods are the least effective methods of contraception.
    • Sterilization is the most effective contraceptive method, but it requires a surgical procedure and may be irreversible. Male sterility is usually achieved with a vasectomy, in which the vas deferens are clamped or cut to prevent sperm from being ejaculated in semen. Female sterility is usually achieved with a tubal ligation, in which the Fallopian tubes are clamped or cut to prevent sperm from reaching and fertilizing eggs.
    • Emergency contraception is any form of contraception used after unprotected vaginal intercourse. One method is the “morning after” pill, which is a high-dose birth control pill that can be taken up to five days after unprotected sex. Another method is an IUD, which can be inserted up to five days after unprotected sex.

    Review

    1. Define contraception. Globally, how prevalent is the use of contraception by fertile married couples?
    2. How is the effectiveness of contraceptive methods typically measured?
    3. List five different types of birth control methods. Which (if any) methods are reversible? Which (if any) methods can prevent the spread of sexually transmitted infections, as well as pregnancies?
    4. What are barrier methods? Give two examples.
    5. Describe hormonal contraception. What is the most commonly used form of hormonal contraception?
    6. What is an IUD?
    7. Generally, describe behavioral methods of contraception, and identify two specific behavioral methods.
    8. Discuss sterilization as a birth control method. How is sterilization typically achieved in males? In females?
    9. What is emergency contraception? When is it used? What are the two forms of emergency contraception?
    10. How does the thickness of cervical mucus relate to fertility? How do two methods of contraception take advantage of this relationship?
    11. Arrange the following methods of contraception in order of typical effectiveness, from the least effective to most effective: birth control pill; fertility awareness method; IUD; male condom
    12. If a newly developed method of contraception had a 35 percent failure rate, would you consider this to be an effective method? Explain your answer.
    13. Which method of contraception prevents ovulation?\
      1. female condom
      2. tubal ligation
      3. birth control pill
      4. fertility awareness method
    14. True or False: A vasectomy prevents the production of sperm.
    15. True or False: If a man and woman have unprotected intercourse four days before ovulation occurs, the woman cannot get pregnant.

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