Video Transcript
In this video, we will learn about hormonal and nonhormonal methods of contraception and will also learn to evaluate their effectiveness. Contraception is a term that describes methods and devices which are meant to prevent pregnancy. These methods and devices fall into two categories, hormonal and nonhormonal contraception. Here, we have a diagram of the female reproductive system. Hormonal methods of contraception, also commonly referred to as birth control, use low doses of estrogen, progesterone, or both to prevent pregnancy in one of two ways.
These hormones may disrupt the menstrual cycle, preventing the release of the egg cell from the ovary. With no egg cell present, fertilization simply cannot occur. Alternatively, hormonal birth control may act by thickening the cervical mucus. This makes it impossible for the sperm cell to enter the uterus or the fallopian tube to fertilize the egg. We removed a little of our diagram to make room for some more notes. Hormonal methods of contraception come in several different delivery methods. And these methods vary most greatly in the frequency in which they need to be taken.
One of the most common methods of hormonal birth control is the pill, a birth control tablet that’s taken orally. Hormones are delivered through the digestive system into the bloodstream. Hormonal birth control pills must be taken at the same time every day to achieve maximum effectiveness. Next on the frequency scale is the contraceptive patch. The patch is like a sticker, and it delivers hormones into the bloodstream transdermally or through your skin. The contraceptive patch needs to be removed and reapplied weekly. Next is the intravaginal ring. This is a soft plastic ring that’s inserted into the vagina near the cervix. And there, it releases hormones to prevent pregnancy. The intravaginal ring has to be replaced once a month.
The contraceptive shot, also called the injection, is an injection of hormones. These must be administered in a professional medical setting. The contraceptive shot, depending on the type, must be taken every one month or every three months. The contraceptive implant is a small plastic device that’s implanted under the skin in the upper arm by a medical professional in a medical setting. From its position within the arm, it releases hormones into the bloodstream. The contraceptive implant can last up to three years, and it must be removed by a medical professional. Finally, we have the hormonal IUD or intrauterine device.
Intrauterine devices vary in their shape, but they all must be implanted into the uterus by a medical professional. The hormonal IUD is made of plastic, and it releases hormones from its position within the uterus. Depending on the type, the hormonal IUD can last from 3 to 7 years. The hormonal methods of birth control vary slightly in their effectiveness, but they’re all greater than 99 percent effective at preventing pregnancy if used effectively. Methods like the pill, the patch, and the ring are administered at home and must be taken on the correct schedule. If the schedule is not followed properly or if other user errors occur, the effectiveness will decrease and the method becomes less reliable.
With doctor-administered methods like injections, implants, or intrauterine devices, the risk of user error is greatly decreased, so these methods tend to be among the most effective. It’s also important to note that hormonal birth control methods are not at all effective in preventing the transmission of sexually transmitted diseases or infections. And that’s because none of these methods block the transmission of bodily fluids. To prevent the transmission of STIs, physical barrier methods of contraception must be used. And we’ll discuss those next.
Barrier methods of contraception work by preventing any sperm from reaching the egg, which prevents fertilization and thus prevents pregnancy. Some barrier methods of contraception are also effective at preventing the transmission of STIs. Condoms are one of the most commonly used barrier methods of contraception. Condoms are thin layers of latex that fits snugly over the penis. If used properly, condoms effectively prevent pregnancy and the transmission of most STIs. Condoms run the risk of failure by tearing or breaking, as well as user errors, such as not being applied properly. Condoms may also come in materials other than latex, but these materials may be less effective in preventing the transmission of certain STIs.
Next, we have the internal condom, also commonly referred to as the female condom. As a contraceptive, this type of condom is inserted into the vagina before intercourse. It has the added benefits of being made of a thicker material that’s less likely to rip or tear and covering some of the external genitalia, which further reduces the risk of transmission of certain STIs. As with other condoms, user error can reduce effectiveness. The diaphragm is a latex dome that’s fit over the cervix. It has to be used along with spermicidal gel, a material which kills or disables sperm in order for it to be effective. Because it does not prevent the transfer of bodily fluids, the diaphragm is not effective in preventing the transmission of STIs.
The sponge is a soft foam disk that contains spermicide. It’s placed inside of the vagina against the cervix, where it prevents sperm from entering the uterus or the fallopian tubes. Like the diaphragm, this method does not prevent the transmission of bodily fluids and thus cannot protect against STIs. Finally, we have the copper IUD, which, like the hormonal intrauterine device, must be implanted into the uterus by a medical professional in a medical setting. However, unlike the hormonal IUD, the copper IUD does not contain any estrogen or progesterone. Instead, it’s made with copper. Copper is a very effective spermicide. It’s also been shown to be effective at preventing the implantation of a fertilized egg into the uterus. While the copper IUD is one of the most common and effective methods of contraception, it is not effective at preventing the transmission of STIs.
At this point, we’ve mentioned a few times the effectiveness of different types of birth control. Effectiveness is usually measured as a percentage, but where does that number actually come from? If we say that a method of birth control is 99 percent effective, we mean that if 100 women use this method of birth control for one year, 99 women out of that 100 will not experience an unexpected pregnancy. But one out of that 100 women will. Effectiveness, when it comes to contraception, refers to preventing pregnancy. Let’s look at it another way.
Here are 1000 dots. And each dot represents a woman. If each of these women for an entire year only use condoms as their method of contraception and assuming that they use the condoms perfectly without any user error, we’d expect them to be about 98 percent effective at preventing pregnancy. So about 20 of these 1000 women would likely experience unexpected pregnancies represented here by the green dots. But we know people aren’t perfect, and mistakes get made. Taking user error into account, condoms are about 85 percent effective at preventing pregnancy. So in a given year, about 150 of these 1000 women would likely experience an unexpected pregnancy, and 850 of them would not. Now that we can visualize what we mean by effectiveness, let’s go ahead and learn how to calculate these values on our own.
With typical use, which includes inconsistent and incomplete usage, out of 1000 women who used the pill for a year, 90 of them experienced unexpected pregnancies. What is the percent effectiveness of the pill with typical use?
To determine the effectiveness, we wanna calculate the percentage of women who do not experience unexpected pregnancies, represented here by the pink dots. So first, we’ll calculate the number of women for whom the pill was effective, and to do that, we’ll subtract the number of women who experienced unexpected pregnancies from the total number of women in our study. When we apply our values, 1000 minus 90 equals 910 women for whom the pill was effective.
In order to convert this number into percent effectiveness, we need to determine what percentage 910 is of the original 1000 women. And to achieve that, we’ll divide the number of women for whom the pill was effective by the number of women in our study and multiply that by 100 percent. Working with our values, 910 divided by 1000 times 100 percent equals 91 percent effective.
Let’s try another example.
The hormonal implant is 99.8 percent effective at preventing pregnancy. Out of our 1000 women, how many of them would we expect to experience an unexpected pregnancy after one year if they’re using the hormonal implant as their method of contraception?
This time, we’re working to calculate the number of these pink dots that should be green on our own. Well, the percent effectiveness tells us the percent of women who will not experience an unexpected pregnancy. So our first step is to determine the number of women for whom the hormonal implant will be effective by multiplying the percent effectiveness by the total number of women. When we substitute in our values, 99.8 percent times 1000 equals 998 women who will not experience unexpected pregnancies. But our question is interested in how many women will experience an unexpected pregnancy, not how many will not.
In order to determine that value, we must subtract the number of women for whom the hormonal implant was effective from the total number of women in the question. When we apply our values, 1000 minus 998 equals two. Out of 1000 women who used the hormonal implants for a year, two would be expected to experience unexpected pregnancies. So now we see two green dots.
Now that we’ve learned to evaluate effectiveness, let’s take a look at our last two methods of nonhormonal contraception. First, we have surgical sterilization. This procedure is called a vasectomy in males, and it’s called tubal ligation in females. These are surgical procedures performed by a doctor in which the fallopian tubes in a female or the vas deferens in a male are cut and then tied shut. In females, this prevents the egg from entering the uterus. And in males, this prevents the sperm from exiting the penis. While highly effective, these are both considered to be permanent procedures. And these surgical alterations are usually impossible to reverse.
Finally, we have the so-called natural methods of contraception. These include the withdrawal method in which the penis is removed from the vagina during intercourse before ejaculation. The other is fertility awareness, sometimes also referred to as the rhythm method. Fertility awareness involves tracking the menstrual cycle and predicting the precise date on which ovulation occurs and then avoiding intercourse on that day, as well as several days before and after.
An obstetrics doctor friend of mine once told me a joke. He said, “What do you call two people who rely on natural methods of contraception?” The answer was parents. The withdrawal method is not effective because sperm might be present in the males bodily fluids before ejaculation occurs. And fertility awareness is not considered to be effective because ovulation dates can change from month to month. It’s important to note that neither of these are considered to be effective methods of contraception.
So now that we’ve learned about all of these different methods of contraception and how to evaluate their effectiveness, let’s take a moment to review what we’ve learned. In this video, we learned what contraception is, the different types that are available, and how they work. We also learned to perform calculations to evaluate the effectiveness of different types of contraception.
