On about Day 14, under direct stimulation from the soaring levels of the gonadotropin hormones, the dominant follicle begins to ooze liquid from a protrusion that has formed on its surface. Simultaneously, it begins to swell, severely weakening the follicular wall. Sometime during the next few hours, the follicle ruptures, with the interior ovum being propelled through the ovarian wall into the abdominal cavity. Ovulation has now taken place.
Most likely, your cervical fluid has reached its last day of slippery eggwhite (and in fact has already begun to rapidly dry up), your cervical position has reached its most fertile (i.e., soft, high, and open), and that morning, you most likely had your last low basal temperature before the thermal shift. For many of you, Day 14 will also produce mittelschmerz, that secondary fertility sign in which an occasional sharp pain around your abdomen verifies indeed that ovulation is about to or already has occurred.
COMPLETING THE CYCLE
The newly released ova is gently drawn in by the fimbria at the end of the fallopian tube, and it now begins its journey through the tube. Assuming there are no sperm to fertilize it, it will disintegrate within the next 6 to 24 hours. Meanwhile, the body’s own hormonal progression continues unabated into the next phase. Back in the ovary from which ovulation took place, the leftover granulosa cells of the dominant follicle are quickly being transformed into luteinizing cells by the high amount of LH. Within hours, these cells have formed the corpus luteum on the interior of the ovarian wall, and it in turn has already begun to secrete heavy doses of progesterone into the body. Waking up on Day 15, you can usually see the result, as this heat-producing hormone triggers your thermal shift.
From Day 15 until about Day 26, the corpus luteum continues to secrete large amounts of progesterone, as well as a modest amount of estrogen. There are several things that immediately result from this combination of hormonal stimulants. With the dramatic fall of estrogen production caused by the hormonal events immediately preceding ovulation, the fertile cervical signs quickly reverse. By Day 16, there is generally no more cervical fluid, and the cervical position has returned to firm, low, and closed.
Still, the corpus luteum continues to release enough estrogen to continue building up the endometrial wall. In addition, progesterone both holds the wall in place as well as contributes to additional endometrial swelling and development, so that by Day 26 the endometrium has reached a thickness of 7–16 millimeters. Were a fertilized egg to reach the endometrium anytime from Day 21 onward (which is likely the first day it could have if ovulation was a week earlier), this uterine shelter would now be ready to nurture the new embryo.
In the days following ovulation, the combination of high progesterone and low estrogen creates other hormonal effects. Most important, the anterior pituitary and hypothalamus are now alerted by the progesterone to sharply curtail production of GnRH, LH, and FSH. Thus levels of these hormones will stay very low from ovulation until near the end of the cycle, or about Day 27. Meanwhile, the corpus luteum itself continues to grow under the initial influence of the LH surge, but peaks in size about a week after ovulation. By Day 21, it can be from 2–5 centimeters, and has generally reached full maturity.
Without the continued presence of LH to sustain it, the corpus luteum now begins to deteriorate. It continues to secrete large but decreasing amounts of progesterone (thus sustaining the endometrium), but by about Day 26, its secretory function is extinguished and cellular degeneration occurs rapidly. Had there been a pregnancy, release of HCG from the developing fetus would have signaled the corpus luteum to remain viable for several more months, until the placenta matured enough to take over its function.
Thus by Day 27, the body’s release of progesterone (as well as estrogen) has plummeted, setting the stage for the hormonal transition to the next menstruation, and the beginning of another cycle. As soon as the corpus luteum dies, the absence of ovarian hormones allows for the initial buildup of FSH. And most dramatically and as previously discussed, the plunge in progesterone production quickly triggers the disintegration of the endometrial wall, and the beginning of your next period. We are now once again where this voyage began.
COMMON TERMS TO DESCRIBE THE MENSTRUAL CYCLE PHASES
Preovulatory: Postovulatory:
Estrogenic Phase Progestational Phase
Follicular Phase Luteal Phase
Proliferative Phase Secretory Phase
KEEPING TRACK OF THE MENSTRUAL JOURNEY
I would like to conclude by repeating what I hope this book has already made clear: While the prototypical 28-day cycle is a useful tool for charting chronological order and biological cause and effect, it is in fact not the cyclical experience of most women most of the time. As you have already learned, typical cycle lengths vary among women from 21 to 35 days, and of course within individual women, there may be variations over time due to stress, diet, and other influences.
You already know that given these factors, it’s not possible to predict the length of the preovulatory phase, and thus the preceding description was accurate as to the order of events, but not as to the actual day of occurrence. I hope that if nothing else, this book has taught you that in matters of fertility, you simply need to chart if you want to know where you are within your cycle.
APPENDIX D
The Contraceptive Effectiveness of Natural Birth Control
Why do mice have such small balls? Because only 10% can dance!
—A JOKE TOLD AMONG BIOSTATISTICIANS WHO NO DOUBT GOT IT QUICKER THAN THE REST OF US
Before any couple decides to use a method of contraception, they should know its rate of effectiveness. The only “guaranteed birth control” is abstinence, and thus, for any sexually active woman of reproductive age, there is always some risk of pregnancy. A critical question in selecting a contraceptive is ascertaining the degree of risk you personally find acceptable.
The Fertility Awareness Method as taught in this book (the Sympto-Thermal Method), if understood thoroughly and always used correctly, is extremely effective in preventing pregnancies. In fact, it is so effective that the weakest link will be the barrier method you use, if you choose to have intercourse during your fertile phase. This is why I would encourage you to abstain, or to at least use two barriers simultaneously during your most fertile days.
If used perfectly and you abstain during your fertile phase (as is done with Natural Family Planning), the chance of becoming pregnant would be approximately 2% over the course of a year. According to the 20th edition of Contraceptive Technology, this is a lower failure rate than any barrier method except the condom, which is also 2%. This means that if you correctly use a barrier throughout the fertile phase, the chance of your becoming pregnant would be close to the method failure rate of the barrier you use. The table here will help to put this data in context.
Indeed, putting contraceptive data into proper social and biostatistical perspective is an important undertaking that is worth the few minutes it takes to read this appendix. You should know that when scientists discuss the efficacy of a contraceptive, there are in fact two different types of effectiveness ratings. One is called “method failure rate,” and refers specifically to the ability of a given form of birth control to prevent pregnancies when that method is used correctly for every act of intercourse. What is considered correct usage is usually defined by set guidelines, often spelled out by contraceptive manufacturers. For the Fertility Awareness Method, correct usage is detailed in Chapter 11 of this book.*
In many ways, what is more important than the method failure rate of any contraceptive is the “user failure rate,” for that is where you can see what occurs in the real world. User failure is generally defined as the rate of unwanted pregnancies for the population as a whole, taking into account both correct and incorrect usage. For example, the method failure of the condom is estimated by Contraceptive Technology at 2%, but user failure is closer to 15%, in part because men sometimes fail to put it on in a way that avoids leakage. This means that o
ver the course of the first year of use, 15% of regular condom users will become pregnant. Fortunately, user failure rates for almost all contraceptives tend to drop after the first 12 months.
As you can imagine, there are some birth control methods in which the method and user failure rates are nearly identical, because the method chosen does not rely on the behavior of the user. Male and female surgical sterilization is the best example of this, with both method and user failure at well below 1%. Their health risks and side effects aside, it’s true that long-term hormonal treatments such as Implanon and Depo-Provera are also exceptionally effective, with both method and user failure rates even lower than sterilization!
Standard birth control pills have a method failure rate of .5% or lower, but typical user failure rises to 5% or higher, depending on the study. This is primarily because women may forget to take the Pill now and then. As the table shows, the condom has a lower method failure rate than the other barrier methods, but all barriers show user failure rates substantially higher than their corresponding method rates. This is because some people are not sure how to use the particular contraceptive or, more likely, because people are somewhat careless in their employment of the various devices.
Where does this leave NFP among the major contraceptive methods? (For the rest of this appendix, I will usually refer to NFP and not FAM, unless dealing specifically with barrier method issues. This is because research on the effectiveness rates of natural methods should not be compromised by barrier method failures.) As I have already stated, the method failure rate of the rules as taught in this book is estimated at 2%. However, the user failure rates are much harder to pinpoint, because quite frankly, the medical literature is filled with studies showing such rates ranging widely, from 1%, to certain studies claiming user failure as high as 20%.*
With such a wide discrepancy in data, is it possible to use the rules with the confidence you need? In fact, yes, very much so, but first you need to know where the data arise and why the discrepancy in reported rates is really not such a mystery. Finally, you need to really think about what the data do imply in terms of the type of people who should, and should not, use NFP or FAM as their contraceptive choice.
NATURAL FAMILY PLANNING: HIGHLY EFFECTIVE, HIGHLY UNFORGIVING
NFP is highly effective when used correctly, but more than any other method, it is extremely unforgiving of improper use, or more specifically, of “cheating.” The reason for this is really quite logical. If, for example, you misuse a diaphragm or condom or even forget to take a Pill, the chances are that for any individual act of intercourse it probably wouldn’t matter anyway since you most likely wouldn’t be in the fertile phase of your cycle. NFP, of course, is the exact opposite, in that if you disregard the rules, you are by definition having unprotected intercourse precisely when you are potentially fertile. To use NFP effectively, you need to understand this, and most important, you need the necessary motivation to avoid pregnancy. As the major studies make clear, if you lack the latter, you will indeed be taking substantial and foolish risks.
As mentioned, various studies show that in the real world, NFP user failure rates vary greatly. Still, 10 to 12% per year seems close to the average reported in the medical literature for the Sympto-Thermal rules taught in Chapter 11. But what is equally important is that all these studies clearly suggest that in a large percentage of pregnancies that occur while “using” NFP, the cause of conception was due to intentional violation of the method rules. Simply put, many couples without sufficient motivation did cheat, and many of those paid the price.*
Ultimately it is a question of semantics as to whether those couples reflect user failure or simply should be considered nonusers, but you can see why NFP and FAM instructors get frustrated when they hear that the method is “not really considered effective.” Indeed, a man using a condom who remains inside too long after ejaculation can certainly be included in the user failure rate. But if just one day he gets lazy and leaves the condom in the drawer, is this seriously a user failure if a pregnancy results? I would suggest that for any contraceptive, intentional and complete abandonment of the method in question reflects a category of non-usage that simply cannot be classified as true user failure.
More than any method, motivation to avoid pregnancy dramatically affects the user failure results. Some of the studies have in fact separated the test groups into motivational categories such that, for example, couples who used NFP to avoid pregnancy were put in one group whereas those who used NFP merely to better space their children were put in another. Not surprisingly, the “spacers” would invariably take greater chances, resulting in user failure rates substantially higher than the “avoiders,” who showed user failure rates as low as 2%. (In fact, user failure rates well below 1% have been documented, but usually when the pre-ovulatory rules are more restrictive than the ones taught in this book—see ‡‡ at the bottom of the chart here.)
NFP, MOTIVATION, AND RESPONSIBILITY
I write all of this not simply to tell you that the medical literature (and mainstream media) is inherently biased against NFP in reporting its effectiveness. The fact is that the numbers do tell us something quite valuable, that each one of you should contemplate before deciding whether NFP is the right method for you. Simply stated, the wide variance in user and method failure rates shows that the very “device-free” nature of the method means that it is extremely easy to slip into a “taking chances” mentality. Indeed, NFP is not a difficult method to learn, and learn well, but it is unfortunately an easy method to practice poorly, which by its very nature can often mean to not practice it at all.
The bottom line on NFP as a contraceptive choice is this: No one truly wishing to avoid pregnancy should be using it if they do not thoroughly understand the rules of the method, and, most important, have the necessary discipline to follow those rules correctly and consistently. If you do not completely understand the method as presented in this book, I urge you to get training through one of the institutions listed here before relying on NFP as a contraceptive choice. Ultimately, natural methods of contraception are only appropriate for those couples with the maturity and focus necessary to not take foolish risks.
FERTILITY AWARENESS, BARRIERS, AND THE FERTILE PHASE: ASSESSING THE ODDS
There are a number of tangential issues related to Fertility Awareness efficacy rates that should be briefly addressed so that all couples can make the most appropriate contraceptive decisions. As I have mentioned, studies have shown that the method failure of NFP is estimated at 2%. However, you should realize that there is a higher risk of pregnancy for those couples who use barrier methods rather than abstain when the woman is fertile.
The statistical reality is fairly intuitive. For those couples who choose to use a barrier method over abstinence throughout the fertile phase, the method and user failure rates of FAM will always be at least as high as the failure rates of the barrier they choose to use. It is for this reason that I suggest that couples who do not abstain use a condom as their method of choice, with at least one other method during the most fertile days. At an approximately 2% method failure rate and 15% user failure rate, condoms are a better barrier than any of the others, as seen in the table here. (Of course the very fact that you’ll know that you are fertile should encourage the type of diligent behavior necessary for keeping your own user failure rate to a minimum.)
For those couples who are determined to absolutely minimize their risk yet do not want to practice abstinence for the full fertile period, there are very reasonable compromises. In reality, the vast majority of conceptions will occur from intercourse that takes place when the woman has wet or eggwhite cervical fluid. This is the time not only closest to ovulation, but also the time that sperm have the best odds of survival. If a barrier is going to fail, it is very likely to happen at this point in the cycle. Fortunately, for most women this phase lasts just 3 or 4 days. Thus for those determined to avoid pregnancy, I suggest you consider alternatives to in
tercourse for that short period of time.
FAM/NFP AND THE RISK CONTINUUM
In discussing the contraceptive rules and the temptation to stray from them, it should be clear that there is in fact a range of possible acts that make up the entire pregnancy-risk continuum. Given this, I would like to address the increased risks associated with what I know to be the specific times most couples are tempted to “cheat.”
Unprotected Intercourse When the Two Postovulatory Rules Don’t Coincide
Some women may notice that the Thermal Shift and Peak Day rules do not always reflect infertility on the same day. The safest approach is to consider yourself fertile until both rules say that you are not (the line “farthest to the right” as described here. Regardless, it is at such times that checking your cervical position can be very helpful in clarifying any ambiguity.
Unprotected Intercourse on Preovulatory Dry Days Before Evening
One of the most common questions I am asked is what risk is associated with unprotected intercourse on preovulatory dry days before evening. As you know, that condition was stipulated to give the cervical fluid a chance to descend to the vaginal opening, lest unprotected intercourse that morning be greeted by unseen cervical fluid wet enough to nurture the sperm that noon. Unfortunately, I have not found any studies on this particular issue (you could imagine the logistical problems in arranging such a survey).
Taking Charge of Your Fertility Page 41