Know More About The Cast Of “The Bachelor” Than You Do About Your “Pill”?
Don’t feel bad, you’re definitely not alone!
This morning, around 160 million women took an oral contraceptive, their Pill, and spent, I suspect, very little time wondering how on earth does such a tiny tablet have such a potentially life-changing action.
But when we look at the time most women will spend trying to avoid pregnancy (decades!) compared with the time they’ll need to produce 2.5 children, it’s obvious that many women will swallow thousands of these tablets across their reproductive lifetime, and that seems to me a good reason to want to understand these Pills at least a little.
Right from its release in 1960, the Pill has been special and a little different – for the first time, here was a tablet prescribed not to prevent, treat or cure disease but instead to give a woman some control over if, and when, to get pregnant.
Nowadays, there’s not one but dozens of seemingly unique Pills available but this choice is really an illusion. Wrapped in fancy packaging are thirty-ish different-looking Pills, yet each is made up of the same one or two hormones. That means that they’re all going to prevent pregnancy in more or less the same way, so if we understand one, we’ll understand them all!
Time for a quick reminder of how we get pregnant?
Sex delivers millions of sperm to the cervix from where they move through a mucus layer into the main part of the uterus before journeying to their final destination - the Fallopian tubes. It’s these tubes that provide exactly the right conditions for fertilization, the fusion of the race-winning sperm with an ovum (egg), to take place.
Once fertilized, the Fallopian tube squeezes the ovum back to the uterus, a journey that’ll take a few days and during which, the fertilized ovum is busily dividing and making more cells. About a week after fertilization, the fertilized ovum arrives at the uterus, and is now a bundle of around a hundred cells and has been re-named a “blastocyst”. Only once the blastocyst has anchored itself to the uterine wall (implantation), can we finally say that a pregnancy has been established.
Key to the monthly ripening and release of an ovum for every potential pregnancy, is the carefully coordinated release of two, relatively unknown hormones from the owner’s brain, follicle stimulating hormone (FSH) and luteinizing hormone (LH). But once a woman’s pregnant, her brain need to know “embryo on board, no more ovulation please” so that there’s no release of those ovum ripening/releasing hormones during the pregnancy. That communication falls to her newly-formed embryo and placenta which send out tons of estrogen and progesterone which, kind of like a chemical text, alert the brain to the ongoing pregnancy.
Imagine the following scenario if a brain isn’t kept in the loop:
A woman, four months pregnant, no longer throwing up but not yet exhausted from hourly visits to the bathroom, decides that some bedroom Olympics are a possibility.
But whoa, her brain doesn’t “know” she’s pregnant, hasn’t stopped her monthly ovulation, and she conceives another baby. Delivery time arrives for the original baby, but she’ll also deliver the later-conceived baby – a baby that’s four months younger and extremely unlikely to survive.
Phew, thank heavens for that dialogue between the placenta and the brain!
So, where do the oral contraceptives fit in?
All of them, without exception, contain a synthetic version of progesterone, one of those placenta-produced hormones that screams “we’re pregnant” to a woman’s brain.
Every progesterone-laden Pill works by telling the owner’s brain, falsely, that they’re already pregnant and egg production needs be halted and the brain does just that – no more monthly egg drops until the pregnancy is finished.
The most famous progesterone-only pill is the “minipill”, mini because it usually has less progesterone than other Pills and because of that, it doesn’t always prevent ovulation.
Therefore, cue several back-up strategies!
When progesterone’s around, that cervical mucus we mentioned earlier becomes thicker, making it harder for sperm to get through and make it to that hot fertilization date!
Remember that squeezing of the Fallopian tube that we mentioned earlier, that moves a fertilized ovum to the uterus?
Muscular contractions of these tubes also help squeeze the ovum from the ovary to the right place to meet the incoming sperm. From its release by the ovary, the ovum has less than 24 hours to fuse with a sperm or it will die - progesterone slows down the movements of the tube so that an ovum probably won’t make it far enough along the tube in time to meet, and be saved by, an incoming sperm!
Phew, way to go progesterone!
The addition of estrogen to progesterone creates a combination Pill, the most-widely used type of oral contraception. Interestingly and I suspect, somewhat surprisingly, although the added estrogen helps to make ovulation less likely, estrogen’s contraceptive benefits are pretty insignificant – it’s there mainly for its ability to reduce side effects such as breakthrough bleeding.
All those awkwardly named compounds on the back of a Pill packet are synthetic versions of estrogen and progesterone whereas the different doses for the various Pill brands are more for side-effect reduction than increased pregnancy prevention. After all, if a top-selling Pill is supposedly 100% effective at preventing pregnancy, that can’t be improved upon but having alternatives with fewer or different side-effects seems to be a good reason to have Pill options.
Talking of 100% effective, when pharmaceutical companies list failure rates for oral contraceptives they typically provide figures for so-called “perfect users”, women who follow every instruction to the letter! In these perfect users, the failure rate for most oral contraceptives is around 1 in 1000 – meaning that for every thousand sexually active, direction-following Pill users, one will get pregnant during the year.
Is it going to surprise anyone if I suggest that many women do not exactly do what they should, and instead, are described as “typical users”. In these women i.e most Pill-using women, the failure rate of the Pill is a shocking fifty times higher – that’s fifty pregnancies for every thousand typical users each year.
Which, before we finish, takes us rather neatly to a brief mention of “his Pill”
Research to create a “Pill for him” has been ongoing for years, with scientists often citing the difficulties of creating a male Pill that has to prevent the production of millions of sperm cells each month, compared with only one or two ova for the female Pill.
Is that the biggest issue here?
If the very people who would experience, first-hand, the consequences of an unplanned pregnancy make so many mistakes with their Pill, can we reasonably expect men to be anything close to “perfect users”?
As with all our posts, our only aim here was to throw a little light on the basic science of this topic.
But if you now have a better idea what to ask when choosing an oral contraceptive, then we’re delighted because ultimately, finding a Pill that works best with both your lifestyle and your own biology?
That just makes “perfect use” a whole lot more likely!
Stay curious,
