Choosing Birth Control

I was recently helping a friend navigate birth control options, and I realized this would make a great blog post. How do any of us choose which birth control options are the best? I know I never had any great guidance in this area as a young adult. In fact, any advice I ever got about sex and birth control was pretty terrible advice, looking back. And even my doctors never really gave me much information. They were all happy to write prescriptions for me, but never once did a doctor actually talk to me about options and their effectiveness. Perhaps midwifery care is different–I have not needed birth control since being in the care of midwives, so I have no personal experience in that respect. This post presents my opinions and research on birth control. It is not meant as a substitute for medical advice. Rather, I hope it may incite you to do more research of your own, take an active role in your health, and engage your health professionals in conversation about your options.

When looking for information on birth control options, there are two important things to keep in mind:

1. The first is whether the method protects against STDs and pregnancy or just pregnancy. Most methods just protect against pregnancy, not STDs, and some STDs are fatal. I am not going to get into STD-prevention too much except to say that unprotected sex with someone also means having unprotected sex with everyone they have ever had unprotected sex with. 
2. The second is the failure rate of the method. You will usually see two failure rates: typical use failure rate and perfect use failure rate. The typical use failure rate represents the percentage of people using this method who will get pregnant in a year with typical use. In other words, your average person using this method with human error involved. The perfect use failure rate represents the percentage of people using this method who will get pregnant in a year if the method is used absolutely 100% perfectly, i.e. in an ideal, perfect world. I think it is better to consider the typical use failure rate, as none of us is perfect, and it isn't realistic to expect that we will never, ever make a mistake. Also, the typical use failure rates come from actual people using these methods in practice, while the perfect use rates come from laboratory statistics. Sometimes you'll see the failure rate, and sometimes you'll see the effectiveness rate. For example, you may see that something is 98% effective, or you may see that it has a failure rate of 2%. They both mean the same thing–just different ways of looking at it. For consistency's sake, I will use failure rates in this post, but you can convert from effectiveness rate to failure rate by subtracting from 100 (i.e. 100 - 98 = 2).

I really love this chart from Wikipedia for comparing birth control methods. I know Wikipedia isn't always the best source of information, but in this case, I think it's pretty fantastic. It has every method I can think of (and some I had never heard of–cycle beads?), and it gives both types of failure rates, type of BC (i.e. behavioral vs. hormonal, vs. barrier), how it's implemented, and how often it requires action. It gives references for every failure rate mentioned. I also really appreciate that it distinguishes between sympto-thermal and rhythm methods, as many charts of this nature combine the two, and you can see that their failure rates are hugely discrepant (1.8% vs 25%!).

OK, using that chart, let's look at a few of the popular choices. The pill is far and away the most popular method of birth control in the US, especially amongst the under 30 crowd. Let's take a look at the pill. Typical use failure rate is 8%. What exactly does that mean? That one out of twelve and a half people using this method in typical use will get pregnant in a calendar year (even though the pill is purported to be 99.7% effective in a perfect world, which would mean 1 out of 333 would get pregnant in a year). To me, that is not good enough. Of course, I had lots of other problems with the pill, so it wasn't a healthy/safe method for me, but besides that, it doesn't meet my criteria for effectiveness. Let's look at a few more:

The pill: 8% failure rate, 1 out of 12.5 will get pregnant in a year (same for the patch, the ring, and the minipill)
Condoms: 15% failure rate, 1 out of 6 will get pregnant in a year
Mirena IUD: .2% failure rate, 1 out of 500 will get pregnant in a year
Pulling out: 27% failure rate, 1 out of 3 will get pregnant in a year
Sympto-thermal: 1.8% failure rate, 1 out of 55 will get pregnant in a year*
Tubes tied: .5% failure rate, 1 out of 200 will get pregnant in a year
Vasectomy: .15% failure rate, 1 out of 667 will get pregnant in a year
The implant: .05% failure rate, 1 out of 2000 will get pregnant in a year
The shot: 3% failure rate, 1 out of 33 will get pregnant in a year
Lactational Amenorrhea/Ecological breastfeeding (6 months postpartum only): 2% failure rate, 1 out of 50 will get pregnant in a year

*a note on the sympto thermal method: I am pretty sure this stat is with abstinence during your fertile window, as using a backup method during your fertile window would reduce the effectiveness to whatever the effectiveness of your backup method is. For example, if you use condoms during your fertile window, then your failure rate would be 15%.

There are more methods in the chart, but I just chose a handful that I think are most common. I think it is interesting that the Mirena is more effective than getting your tubes tied. I never would have guessed that. Looking at these rates, it doesn't seem to leave a lot of good options for young people. It is my understanding that IUDs are typically only recommended for women who have had a child already. Some of the other highly effective options are permanent, which obviously wouldn't be good for someone who might want to have children in the future. The implant and the shot would require procedures at the doctor's office, which may be fine for some. In terms of the choices that the patient can manage herself, the most effective is sympto-thermal, followed distantly by the pill, condoms, and pulling out.

There is also the option to combine methods. I'm going to explain how to calculate the failure rates when you're dealing with two methods, but if the math makes your head spin, just skip ahead to the examples. First, convert from a percentage to a decimal by moving the decimal two places to the left. So 2% becomes .02, .5% becomes .005, .15% becomes .0015, 15% becomes .15, and so on. Once you have the decimal values for both methods, multiply them together. I will just choose a few combinations as some examples:
The pill (8%, or .08) + condoms (15%, or .15): .08 x .15 = .012, or 1.2% failure rate, 1 out of 83 will get pregnant in a year
Sympto thermal (1.8%) + condoms (15%): .018 x .15 = .0027 = .27%, 1 in 370 will get pregnant in a year*
The pill (8%) + pulling out (27%): .08 x .27 = .0216 = 2.16%, 1 in 46 will get pregnant in a year
Mirena (0.2%) + condoms (15%): .002 x .15 = .0003 = .03%, 1 in 3,333 will get pregnant in a year

*Just to clarify what this means: in this case, you'd be using condoms always and using abstinence during your fertile window

Keep in mind that some methods are incompatible. For example, you can't combine two hormonal methods (like the pill and the patch), and you can't combine anything hormonal with sympto-thermal, as the hormones will interfere with your fertility signs. Condoms can pretty much be combined with anything, and they also protect against STDs, so they are often a good choice as your second method, but I think it is still important to calculate your total failure rate. Sometimes combining two methods still isn't as effective as just one method, depending on what you choose. For example, either sympto-thermal or lactational amenorrhea is more effective alone than the pill plus pulling out. And mirena is more effective itself than sympto-thermal plus condoms.

One more note on math, if you're trying to convert from a failure rate percentage to 1 out of xx odds, you would take 1 divided by the rate (converted from percent to decimal), so for something with .2% chance (i.e. Mirena), you would take 1/.002 = 500, which means 1 out of 500 people would get pregnant in a year. 

Of course there are other things to think about, like cost, side effects/longterm effects, safety, how much control you have with each method, and how often you need to manage the method. I hope this provides some helpful information or something to think about. And I encourage you to share this information with others, especially young women. We need to have these conversations, even though they are sometimes tough.

Which methods have you tried? How did you decide what was best for you?