Continuing in our vein of basic science posts on female reproduction, we're going to take a bit of an aside (and this is VERY relevant for the paper that Sci wanted to blog about that needed so much background). We've covered the basic anatomy, the hormones, and the monthly cycle. But what about...when you don't want to ovulate?
What about oral contraceptives?
Of course, they aren't all oral anymore. Now we've got the patch and the ring, and I'm sure pretty soon we'll some sort of nasal insert (maybe something that looks like a nose ring?) for those who cannot be bothered with either a patch or a ring, let alone a pill.
So what about these?
(I do seriously hope they make the patch in darker tones than that. I do not think it would be hard to make a patch that actually matches your skin tone, so I really hope they market them)
(on the other hand, if you wanna make me a birth control absorbed through the skin that can be worn as a RING, and make it to look like the One Ring, I WILL wear it. Drug companies, take note.)
So, remember this?
Of course you do! Excellent. Let's go.
As you can seen above, increases in estrogen (occurring in a stepwise fashion) occur throughout the first 11 days or so of the cycle, only to drop off massively right before ovulation. This drop-off actually TRIGGERS the surge in LH and FSH, which in turn cause ovulation.
So if LH and FSH surges are required for ovulation, what should you do to prevent ovulation? Stop the surge obviously. And HOW exactly does the pill do that?
The pill has many formulations, but most contain synthetic estrogens and progestins, and some contain only progestin. What they do is keep the levels of circulating estrogens and progestins HIGH. If you keep the levels of circulating estrogens high, you avoid that big drop at day 11. That big drop prevents LH and FSH from increasing, which prevents ovulation. Deceptively simple. Looks like this:
On the top you can see the normal menstrual cycle, this time with LH and FSH on top and estrogen and progestin on the bottom. This picture shows a progestin only oral contraceptive. You can see on the bottom that the progestin levels are kept high, and this means the Lh and FSH (green and yellow lines) never spike (see third panel).
Of course, you need to be careful. You don't want to give super high amounts of hormones (there are worries about cardiovascular problems and cancer here), the goal is to give just enough that the body doesn't notice the usual drop in estrogens, and fails to release LH and FSH. The lowest dose possible is often considered best, and this has actually become something of a problem due to rising weight in the US. When people are of higher weight, they need to take higher doses to prevent ovulation, and a lot of times, the pills are only made for a weight within the "average" range.
However, even if you DO ovulate despite your birth control (for the progestin-only pills, you still ovulate roughly 50% of the time), there's still little chance that you will get pregnant. Why, you ask? Because higher levels of estrogen and progestin have another effect on the body. They thicken the vaginal mucosa (yer fluids). This thickened mucosa is no fun for sperm to swim through, and makes it much more difficult for fertilization to occur. It's nice to know there's an extra barrier there, just in case.
Wait. If you don't ovulate (usually) on birth control, why do you menstruate? Well, technically speaking, some physiologists don't believe you need to. It could be possible for you to go some time without menstruating if you're not ovulating, and this is the idea behind the three-month birth control types like Seasonale. However, many people still feel more comfortable menstruating every month.
So every month, when you've gone through three weeks of the birth control packs, you keep taking pills, but you menstruate anyway. What happened? The pills you are taking during that week are actually placebos (or, in the case of the ring or patch, you take it off during the days you are supposed to menstruate to stop the hormone influx). They don't contain any estrogen or progestin in them, and when the estrogen and progestin levels drop off (as at the end of a normal cycle), your body does its usual thing and shed the endometrial lining, and you menstruate. For the progestin only pills, there is no break between packs (no placebos), as a constant dose of hormone is needed to prevent ovum development. This also means that progestin-only pills have to be taken much more consistently than the combined estrogen/progestin types (estrogen/progestin types can take a leeway of up to 12 hours, progestin-only has a leeway of 3 hours).
Placebos, did you say? I'm taking placebos!?! Does that mean that I can get pregnant if I have sex during my period? Nope. Because if you were taking the pills on time for the rest of the month, you haven't ovulated. There's nothing there to fertilize.
Keep in mind, though, that oral contraceptives should NOT be skipped. You're still getting a dose of estrogens every day. If you miss a pill or two, the estrogen levels will DROP sufficiently to cause that surge in LH and FSH, leading to ovulation. So if you don't want that to happen, don't skip.
weight gain: A couple of studies found that people didn't like the pill because it caused weight gain. That was a study done in 1998 in 15-19 year old girls. However, the vast majority of studies have found that the lower doses of the pill do not have significant weight gain problems associated with them unless you are having an unusual reaction. Some scientists think that women notice weight gain when they start taking the Pill because of WHEN they start it. For example, when you go to college, when you start puberty and start putting weight on, when you get married and move in together, etc. But the scientific consensus is that combined oral contraceptives (like the pill, patch, or ring) do not cause weight gain above normal. Some weight gain IS seen with the progesterone only formulation when given as an injection or IUD. Some women will notice increases in breast size and tenderness during the first few weeks. The tenderness usually goes away. The size often stays. Some women don't mind this, but some do. Up to you.
acne: The pill is sometimes prescribed to help with acne, by evening out the hormone fluctuations that result in monthly breakouts. In some rare cases, it can make acne worse, but most of the time we think it makes it better.
heart issues: The pill can change blood clotting, cause higher blood pressure, and increase the odds of things like stroke and heart attack. Keep in mind though, the risk is VERY small, and if you're young and healthy, you're probably fine. However, to reduce the risks, some women prefer the ring. Because it goes up inside the vagina, the local levels of hormone are more effective and the circulating blood levels of hormone don't need to be so high. OTOH, it's a ring up in your vagina, with some people find rather inconvenient.
Other complaints: studies vary on libido, some women find their libido is better because they aren't so worried about getting pregnant, others find it's worse. The pill can also worsen symptoms of depression, particularly the progestin only varieties, but scientists are divided on this point as to whether or not it's a very common side effect, or more rare.
And that's my aside on how oral contraceptives work. Next time, it's back to the female reproductive cycle. Get ready for Pregnancy!