The logistics of using birth control to regulate menstrual cycles

July 18, 2007 7:46 PM

Can birth control prevent ovulation a day or two before it occurs?

I'm down for an appointment this Friday to get on birth control pills. My period tends to fluctuate between 30-40 day cycles, but calculated against a 28 day cycle, ovulation would be this weekend.

If I started the package on Friday, would I end up having my period in three weeks' time, or is it too late in the cycle to regulate this one?

posted by Phire to health & fitness (21 comments total)

It's probably too late. It takes about a week for the pill to be useful as a contraceptive, IIRC. That'll be your last ovulation for a while - you don't ovulate while on the pill.
posted by cobaltnine at 7:51 PM on July 18, 2007

It's not the contraceptive effects I'm interested in so much, for now. My period if left to run its regular course would wreak havoc with the only week off (and the activities planned) I have this summer...
posted by Phire at 7:59 PM on July 18, 2007

You will ovulate, and it will regulate the first period.
posted by Steven C. Den Beste at 7:59 PM on July 18, 2007

If I recall correctly, you'll be instructed to start the Sunday after your period. (Or, since you mention Friday, you can start midweek, but I believe the instructions will still be to start after your next period.)

Though I think cobaltnine is correct that it takes a week, the standard advice I've heard is to use a backup birth control method for the full first pack of pills.

Also, of course, ask your doc at the appt what you can expect. (On preview, oh I see. So mention specifically that you'd like to skip a period.)
posted by juliplease at 8:04 PM on July 18, 2007

What do you mean by that? I will ovulate, but not 'get the period' until three weeks later? Or I will ovulate and my period will be shorter and lighter, as prescribed?
posted by Phire at 8:05 PM on July 18, 2007

You don't ovulate while you're on the pill generally, you will ovulate this time around, this weekend. Here are more pill facts. You are usually told to start the pill after your period and the deal is that you take three weeks of pill and then you have a week "off" which is when your period happens. Obviously talk to your doc, but the easiest way to move your period around it to move around when you're taking the pills, either to more conveiently space your period or what have you. So, what you said is right, it's too late in your cycle to regulate this one, unless your doc gives you a non-standard way to take your pills.
posted by jessamyn at 8:23 PM on July 18, 2007

Phire, do you know how the pill works? The theoretical basis behind it?

(I don't want to write at length about that if you do.)
posted by Steven C. Den Beste at 8:32 PM on July 18, 2007

I've done the basic reading, yeah. As jessamyn mentions, it basically prevents ovulation, no? The 'period' you get doesn't actually include an egg. I'm a bit fuzzy on how the hormones interact with an already ovulated egg, or how fast the hormones work. I think that's the origin of my confusion...
posted by Phire at 8:47 PM on July 18, 2007

I'm a bit fuzzy on how the hormones interact with an already ovulated egg, or how fast the hormones work.

The short answer to your question is that the hormones DON'T have much to do with an already-ovulated egg which is one of the reasons doctors say use a back-up method of birth control for the first month and why you start your pills after you period. Some morning-after pills use different combinations of hormones to prevent implantation of an already (possibly) fertilized egg which may be why you're confused.
posted by jessamyn at 8:52 PM on July 18, 2007

So in short, there's no way to prevent my period this close to ovulation? *sad*
posted by Phire at 8:57 PM on July 18, 2007

There's also a good chance you'll be spotting for a while, as well, while your body gets used to the pill. Buy some panty liners now. If the spotting doesn't go away in 3 months, you should talk to your doc about changing brands.
posted by cgg at 9:00 PM on July 18, 2007

FWIW I started my hormonal BC around when I'd normally ovulate and my first cycle of BC withdrawal bleeding was noticeably lighter then my normal period. My personal theory as to why involves psychosomatic-ism (made that word up) and guessing that the lining of the uterus doesn't build up to full thickness until right before the normal period.

(And don't let talk of spotting scare you off. It's still icky because, you know, goo and blood and stuff, but it doesn't hurt which makes it miles better.)
posted by anaelith at 9:32 PM on July 18, 2007

Hokay, ignore this if you aren't really interested.

Sexuality in human adults is governed by a hormone feedback loop. In men, the hypothalamus monitors testosterone levels in the blood and produces a hormone called Gonadotropin Releasing Hormone (GNRH), in a somewhat inverse relationship to the amount of testosterone it sees. Too much testosterone, less GNRH. Too little testosterone, more GNRH.

The pituitary detects the level of GNRH and proportionally releases two hormones. Those are called Leutinizing Hormone (LH) and Follicle Stimulation Hormone (FSH).

LH and FSH are detected in the testicles. Testosterone is released in proportion to the amount of LH detected, and FSH causes sperm production. In men, this feedback loop is analog, and though the setpoint target in the hypothalamus varies (over the course of a day, and over the course of the year) the whole system runs proportionately.

GNRH, LH, and FSH are also involved in governing a woman's system, as are the hypothalamus and pituitary. But where in a man the system is analog and proportional, in a woman it runs "to the rail". The hormone levels are step functions, all the way on or all the way off.

The hypothalamus monitors estrogen levels, and if there isn't enough it produces GNRH. The less estrogen, the more GNRH. But there's no immediate proportional response in estrogen production, so the GNRH level maximizes. This causes the pituitary to produce large amounts of LH and FSH.

LH causes the uterus to have a period. FSH causes follicles in the ovaries to mature and prepare to release eggs. On each period several follicles will respond to FSH, a race condition, but usually one wins the race. When that happens, it releases its egg and the follicle starts producing estrogen. (If two tie the race and if both eggs are fertilized, the result is fraternal twins.)

That estrogen is what the hypothalamus wanted to see, even though it took several days for that response. It shuts down the GNRH, which shuts down the FSH and LH. (Actually, the hypothalamus is trying to be proportional again, but the estrogen level produced by the follicle doesn't decline as FSH declines, so the hypothalamus backs off all the way to zero.)

The egg which was released travels slowly down the fallopian tube, and usually enters the uterus unfertilized and exits. After something between 15 and 25 days the follicle stops producing estrogen, and then the process described above repeats as the hypothalamus once again cranks up the GNRH level.

But what if the egg gets fertilized while in the fallopian tube? Then by the time it reaches the uterus it has divided several times, forming a blastula, which embeds in the wall of the uterus, and you're pregnant. Shortly thereafter the uterus starts producing yet another hormone, progesterone. (It takes several days, but it happens before the follicle stops producing estrogen.)

Hormones are chemical signals with very specific meanings. LH means "Prepare the uterus for a potential pregnancy." FSH means "Prepare and release an egg." Estrogen means "Egg has been released." Progesterone means "Pregnancy in process". Progesterone continues to be released as long as the pregnancy lasts, and progesterone makes the hypothalamus just as happy as estrogen does. As long as it sees either of them it doesn't produce GNRH. Which means no FSH is produced, which means no eggs are released from the ovaries.

SO... what's the pill? The pill is a chemical analog of progesterone, which is sufficiently similar so that all the receptors treat it as being the same, but which is sufficiently different so that it's broken down much more slowly by the liver.

A month (28 days) of pills consists of 21 pills which contain progesterone analog followed by 7 pills which contain nothing at all. During the 21 days of progesterone, the hypothalamus is being told that you are pregnant. After the 21st pill, the progesterone stops, and the body treats that like a miscarriage.

At that point the hypothalamus starts producing GNRH, thus LH and FSH. The uterus menstruates, and follicles in the ovaries start to prepare eggs. But before any of them can finish the job, the 7 days are over and pills with progesterone once again announce pregnancy. The hypothalamus turns off the GNRH, thus FSH, and the follicles stop. No egg is produced.

There is some latency involved in all this; the step functions don't have instantaneous transitions. That's because the half-life of a lot of these hormones in the blood is moderately long (usually hours), and you have to go through two or three half-lives before the levels are down enough so that the receptors stop responding to them. (Hormone half-lives vary enormously. The half-life for adrenalin is only a couple of minutes.)

So you asked what would happen to an expected ovulation event on Sunday if you started taking the pill this Friday.

It probably wouldn't prevent it. It takes a while for the progesterone level to build up, for the hypothalamus to detect it, for GNRH levels to fall, and then for FSH levels to fall. Two days isn't enough; a follicle in the ovary would complete its work before the FSH level was reduced enough to shut it down.

On the other hand, it would definitely affect an anticipated period in a couple of weeks. By then progesterone level would be high enough for the hypothalamus to detect, which would mean that it would not produce GNRH, thus no LH, and there would be no menstruation. Only when you got to the first batch of drug-free pills (the final 7) would you have a period.

And I apologize if that's more than you wanted to know.
posted by Steven C. Den Beste at 9:44 PM on July 18, 2007 [16 favorites]

Ask your doctor about getting a couple of extra cycles of pills. I hear that it is medically safe to avoid "periods" for up to 3 cycles by taking the active pill cycles back to back. If you're worried about your period interrupting your activities this summer, that might be your best bet.
posted by Araucaria at 10:13 PM on July 18, 2007

NB, you want to make sure that you have stopped ovulating completely before starting the back to back cycles. And again, IANAD, it's just something I remember hearing about recently.
posted by Araucaria at 10:16 PM on July 18, 2007

I hear that it is medically safe to avoid "periods" for up to 3 cycles by taking the active pill cycles back to back.

It's probably safe for longer than that. After all, a pregnancy lasts for 9 months.
posted by Steven C. Den Beste at 10:19 PM on July 18, 2007

Excellent, Steven C. Den Beste, that's exactly what I needed :D If I could push back my period by even a week, it would play out beautifully, and that seems to be exactly what starting the pill this Friday will do. Thank you very much!
posted by Phire at 10:37 PM on July 18, 2007

I am not a doctor. If your doctor tells you not to start it this week, you should do what your doctor says and not start it.
posted by Steven C. Den Beste at 11:07 PM on July 18, 2007

Rats. I just did some looking up, and I botched some details and simplified some things. What I wrote is correct in essence, though.

Sorry about that.
posted by Steven C. Den Beste at 11:28 PM on July 18, 2007

If delaying the start of your period is your main concern, rather than contraception, ask your doctor for Norethisterone tablets. In the UK it has a license for exactly this purpose: 5mg x3/day starting three days before the expected date of your period.

Disclaimer: IAAGynaecologist, but not in your country, and this is not a substitute for advice from your actual doctor etc etc etc.
posted by roofus at 2:28 AM on July 19, 2007

Phire, I hope you get your period delay wish, but I just want to warn you not to get your hopes up. The first month or so of going on any sort of hormonal birth control can result in some unexpected side effects. For example, I had gone off the pill for 6 months and then went back on it. The first month I had "breakthrough bleeding" and spotting for 3 weeks straight.

You could always encourage your period to come early, using my non-scientific but foolproof method. Basically, remove any feminine products from your purse, pockets, desk drawer at work, etc. Then wear your nicest, most expensive pair of white panties, and light colored pants. Make sure you have nothing convenient to wrap around your waist like a sweater.

In my experience, this has never failed to induce a period.
posted by tastybrains at 6:18 AM on July 19, 2007