Does the 'morning-after' pill or I.U.D. always abort?

Having set out the scientific facts regarding the various methods of post-coital abortifacient drug use, one final critical question must be addressed. Is there any stage during a woman's cycle when she can reasonably take the MAP or use an IUD without risking the loss of a human embryo? To fully appreciate this discussion it is critical to note the following interconnected events:

(a) ovulation determines the opening of the "fertile window",

(b) this "fertile window" is open for 6 days, being the first five days prior to ovulation and the day of ovulation itself, (1)

(c) the day of ovulation, and hence the "fertile window", is not inflexibly fixed to the middle of a cycle, either in regular or irregular cycles, and

(d) "The implantation window is a short interval during the mid-secretory phase, when the endometrium is most receptive to blastocyst implantation. It begins on days 20-24 of an ideal menstrual cycle or 6-10 days after the LH surge and is believed to last less than 48 hours." (2)

Research by Wilcox, Dunson and Baird (2000) has reported that the only days with close to a zero probability of ovulation (i.e., less than 1%) and hence conception, were the first two days of the menstrual cycle. Ovulation was reported to have occurred as early as the eighth day and as late as the 60th day (in prolonged cycles.) Statistically, "an estimated 2% of women were in their fertile window by the fourth day of their cycle and 17% by the seventh day (based on 213 women). This percentage peaked on days 12 and 13, when 54 % of women were in their fertile window. Among women who reached the fifth week of their cycle, 4-6 % were in the fertile window."

Also of significance was the finding that even women with regular cycles had a 1- 6% probability of being within their window of fertility on the day the next period was due. Between days 6 to 21 of a regular cycle, at least 10% of women were in their fertile window. Highlighting the large measure of variation in the probability of ovulation was the finding that 20% of pregnancies occurred with ovulation being before day 13 and 22% of pregnancies were due to ovulation after day 21.(3)

Based upon these data, and reports indicating that "most women do not keep a record of their menstrual periods",(4) leading to a high level of uncertainty of cycle status, there is no scope for the licit use of the various forms of post-coital pre-implantation drug use, even during the first few days of menstruation. Even if a woman were able to have an ovarian ultrasound performed to determine the state of development of an emerging follicle, plus have blood and/or FSH and LH levels determined since these act as ovulation inducers and stimulates, plus have oestrone-3-glucuronide and pregnanediol-3-glucuronide levels determined since these are post-ovulation markers, there still remains the possibility that a woman could ovulate very early or late in her cycle due to the duress of a sexual assault. Yet, for many women this debate is redundant; many countries have now made the MAP available as a non-prescription product, requiring no supervision by a physician.

And to recall three early points regarding key aspects of sperm fertility:

(1) The use of any form of emergency birth control 'the next morning' would be many hours too late for any purported anti-sperm activity.(5)

(2) Under the influence of uterine contractions, rapid transport of sperm-sized spheres to the Fallopian tube can take only one minute.(6)

(3) Brito (2005) reported that when human sperm was subjected to "three concentrations of levonorgestrel (LNG) comparable to the levels found in serum following ingestion of LNG as emergency contraception ... there is no influence in the fertilizing capacity of spermatozoa." (7)

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(1) Wilcox AJ, Dunson D, Baird DD. The timing of the "fertile window" in the menstrual cycle: day specific estimates from a prospective study. BMJ 2000; 321:1259-1262

(2) Aghajanova L, Hamilton AE, Giudice LC, op.cit.

(3) Wilcox AJ, Dunson D, Baird DD. op.cit

(4) Glasier A. Emergency postcoital contraception. op.cit., p. 1043

(5) Ashraf H, McCarthy M. UK improves access to "morning after pill". Lancet 2000; 356:2071

(6) Kunz G, Beil D, Deininger H, Wildt L, Leyendecker G. The dynamics of rapid sperm transport through the female genital tract: evidience from vaginal sonograph of uterine peristalsis and hyperosalpingoscintography. Hum Reprod 1996; 11(3): 627-632

(7) Brito et al, op,cit.