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Contraceptive Pill

by J.C. Willke MD

Contraceptive pills contain, in differing dosages to be taken in different combinations during the month, two synthetic female hormones.  They contain estrogen and the second hormone, progesterone.  Sometimes that's called the "pregnancy hormone."  This hormone is normally formed in a woman's body in the second half of her monthly cycle.  Its function is to prepare the lining of the womb for the nesting of the new human, if fertilization has occurred that month, and it is the withdrawal of this second hormone at the end of the month, if there is no pregnancy, that produces the sloughing of the lining of the womb and its passage from her body, a process called "menstruation."  Contraceptive pills used today contain varying percentages and dosages of these two hormones.  The pills are usually taken three weeks out of a four-week month.

How do these pills work?  They basically have three effects.  The first effect is the thickening of the mucous plug at the opening of the cervix, the mouth of the womb.  This provides something of a natural barrier to the passage of sperm into the womb.  This is a contraceptive function, as it prevents the union of sperm and egg.

There's a second effect, which usually is the primary effect, and that is the suppression of ovulation.  A projected ovulation is simply blocked and does not occur.  The sperm may well be deposited in her female tract; they may swim through her tubes and out to the ovaries, but if there is no egg to fertilize, then we have a primary effect, an action technically called "temporary sterilization"-or, in more common, but less accurate language, "contraception."

There is a third effect of the contraceptive pill.  This effect is on the lining of the womb.  What this does is to harden the lining of the womb-we say, make it hostile to implantation to this one-week-old embryo.  If this is the function that prevents "pregnancy" that month, then it is implantation that is prevented.  And this implantation, if prevented, kills a tiny one-week-old baby.

So the widely used contraceptive pills have three functions, any one of which is said to "prevent" pregnancy.  Only two of the functions, however, actually do prevent pregnancy:  (1) the barrier mechanism of the mucous plug at the cervix, (2) the suppression of ovulation.  The third function, however, does not really prevent pregnancy, but rather produces a micro-abortion at one week of life.

The original contraceptive pills, 30 years ago, contained a high dose of the hormone estrogen.  Because of this, almost 100% of their effect was to suppress ovulation.  But there were side effects from this high estrogen content, and that was primarily the substantial risk of blood clots.  If these broke loose and went to the heart, lung or brain, they were very dangerous, and sometimes fatal, even for young women.

During the years since that time, the drug companies have progressively reduced the amount of estrogen in the pill so that now, depending on the pill, it is only 1/20th, or even 1/30th as much as it was when the pill was first introduced.  With this reduction in estrogen, there has been a drop in the complication of blood clots, but, with the reduced estrogen, there has been an increase in what we call "breakthrough ovulation."  The estrogen level is so low that it doesn't suppress ovulation all of the time anymore, and sometimes there is what we call a breakthrough ovulation-ovulation which breaks through the effect of the drug and is simply a plain old ovulation.  It just happens.  Fertilization, then, can occur.  But if fertilization occurs, implantation within the nutrient lining of the womb is prevented by another action of the same pill.  That action is a hardening of the lining of the womb.  What occurs, then, is an induced micro-abortion at one week of life.

How frequent is breakthrough ovulation in a woman taking a low-estrogen contraceptive pill?  Well, let's take a high estimate-20%.  Probably lower than that.  How frequently does pregnancy occur when there is an egg or an ovum waiting?  Probably not much more than two or three times out of the twenty.

So if we use a high figure, a 20% breakthrough ovulation, that would mean a two or three percent fertilization rate.  But, as a matter of fact, pregnancy occurs only about 1% or less of the time, so, in the other 1 or 2%, fertilization does occur, implantation cannot occur, and the little embryonic baby dies.

The bottom line, then, for the commonly used contraceptive pill is this:  In 97 or 98% of the time, the effect is one of preventing pregnancy.  But, in perhaps two or more percent of the time, the effect is abortifacient.  There is no way in the normal clinical practice of obstetrics of knowing which is happening, or when.