Fetal sex preselection – illustrated

Ovulona and logo

In the document attached to this post (below), we say:

The following illustration is adapted from one of our slides. The slide indicates how baby gender pre-selection works or rather how it will work when the Ovulona™ is launched in the marketplace. The data were generated in a clinical study performed with our early prototype. The data show the morning and evening cyclic profiles from one of the baseline subjects studied by the gynecologist Dr. Benedetto of the University of Turin, Italy.

This is a record of one menstrual cycle of a 30-years old woman participating in the Italian clinical test. The record shows the typical features of the Ovulona cyclic profile. In these early tests, the measurements were taken twice daily (morning and evening) in order to see if a time-of-day effect could be observed, and the BBT (Basal Body Temperature) was taken in the usual manner as a reference parameter.

Here is the slide:

The three-day fertile window how-to

The record shows that the features of the cyclic pattern – reproducible because the same features were also obtained by other women – make it possible to determine the boundaries of the fertile window. The precision is such that it allows for correlation of fertile day 1 with trying to conceive a boy, and correlating fertile day 3 (the ovulation day) with trying to conceive a girl. Correlating each of the 3 fertile days with the indicated likely gender of the baby conceived on the given day is based on the results of certain studies by other investigators (John France et al.), as referenced below.

The outcome of their clinical work is consistent with the finding a decade later – by other investigators in 2001 – that male spermatozoa (Y-chromosome-bearing sperm) live longer than female spermatozoa (X-chromosome-bearing). The France et al. results from timed-conception birth-giving patients stand by themselves but it is nice to have available the separately produced physiological rationale that explains those results; read on.

And here is in a nutshell the clinical trial evidence for the 3-day fertile window:

3-day window data from a study by John France et al.

This is a re-plot of their data (from 55 births) of birth counts as a function of the cycle day, whereby the outlier data points were considered to belong, in fact, to the counts of the three days of high birth counts, the outliers having been due to their inaccurate and unreliable methods of estimating the time of ovulation. The problem will be resolved when, instead of the old imperfect methods of guesstimating ovulation, people will use our Ovulona monitor.

More details are in the attached file: Fetal sex preselection – illustrated

The file is a description of the origin (including the best clinical trial evidence available to date) of the 3-day fertile window.

The 3-day window of high conception probability is unequivocal (there is no doubt that the data show that window). The low birth counts on the flanks of this 3-day group are data point outliers due to errors in the investigators’ estimating the ovulation day.

The 3-day group of high birth counts is in the data whether we simply ignore the outliers or add them to this group. This is no unreasonable massaging of the data because the investigators’ methods of estimating ovulation timing are well known to have high error bars associated with their ovulation-day estimation.

The 3-day fertile window is also supported by evidence published in the NIH paper referenced below. The 3 days of unequivocally high probability of conception are clear in their data, which is all based on analysis of first morning urine samples for metabolites of estrogen and progesterone that they considered “highly concordant with the peak urinary concentration of luteinizing hormone (which corresponds approximately with the day of ovulation)”.

The NIH researchers (Wilcox et al.) did not consider the inaccuracy of their estimated ovulation despite their having acknowledged that their method only “approximately” assessed the timing of ovulation. Unlike France et al., they did not use more than the one method of estimating ovulation. They simply accepted that, in addition to the three days of high conception probability, their data also contained three early days of low probability of conception – as though 3 to 5 days old spermatozoa made a woman a little bit fertile, despite the 3-day maximum lifespan of the sperm.

We account for their days of low conception probabilities in the same way as above, in terms of data point outliers. A probable cause of their low conception probabilities in the early pre-ovulation days (days -5 to -3), additional to their merely approximately estimating ovulation timing, was the possible delay between the indirectly monitored systemic hormone signals and the actual ovulation. Ovulation (day 0) in their study was not detected but only assumed based on urine hormone metabolite measurements. Despite this and other flaws in their study design, the evidence of the 3 days of high conception probability is there, similar to the data of France et al.

The Wilcox et al. technique of tracking certain ovarian hormones in the urine does not monitor the complex mechanism of folliculogenesis. Any mismatch between the ovarian and the brain hormone signals goes therefore undetected, and their estimate of ovulation timing is indeed very approximate. Of the other study design flaws, let’s mention the artifice that any “intercourse recorded on a given morning was assumed to have occurred the previous day”. This incongruous assumption artificially produced the day 1 conception probability of zero.

As for their low probability data for days -5 to -3, we can consider them to be data point outliers because a pilot study with our prototypes produced evidence of ovulation delays of up to 3 days after urinary LH detection (even 4 days in one of the 21 cycle records, monitoring urinary LH, Peak mucus, and Ovulona prototype). Ref.: https://biozhena.wordpress.com/2010/03/28/folliculogenesis-in-vivo%E2%84%A2-monitoring-is-far-better-than-current-home-use-fertility-self-help-tools/

Further, in support of the fetal gender preselection based on fertilization timing, a “statistically significant lower proportion of male births among conceptions that occur during the most fertile time of the cycle”, meaning at or near estimated ovulation, was found in a 1991 Johns Hopkins University meta-analysis of six NFP studies, cited below in the References.

Similar conclusion came out of an assessment of medical literature in 1989: “More females are conceived when coitus occurs relatively close to ovulation…”. The view of the cited group at University of Washington School of Medicine, Seattle was that the “influence of coital timing on the sex ratio is overall quite subtle and is not a practical method to alter the sex ratio for individual couples” (for citation see References). We would say that our purpose is to offer a means with which to make it practical…

Besides the referenced reviews of clinical outcomes, there is the above-mentioned evidence from a premier infertility treatment institute (G. Hodgen et al., see References) that male spermatozoa (Y-chromosome-bearing sperm) live longer than female spermatozoa (X-chromosome-bearing).

Therefore, intercourse two days before ovulation favors the conception of a boy because only the male Y-chromosome bearing spermatozoa live that long. The male sperm live long enough to be available for fertilization when ovulation releases the ovum (egg) from the ovulating ovarian follicle. Whereas the female X-chromosome bearing spermatozoa have a chance to produce a baby girl only if intercourse takes place on the day of ovulation, because of their short lifespan.

Note that these are probabilistic indications, hence the labeling “try for a boy” and “try for a girl”. Certainly, we would not say that on the given day you will definitely conceive as indicated.

That should be no surprise because you know that conception is a matter of chance, a probabilistic matter, in the first place. More on this topic of conception probability is in the post Difficult conception tied to pregnancy complications – addressed.



France et al. paper with data on fetal sex pre-selection, 3-day fertile window:

J.T. France, F.M. Graham, L. Gosling, P. Hair and B.S. Knox, “Characteristics of natural conception cycles occurring in a prospective study of sex preselection: fertility awareness symptoms, hormone levels, sperm survival, and pregnancy outcome”, International Journal of Fertility 37 (4), 224 – 255, 1992.

Wilcox et al. NIH paper:

A.J. Wilcox, C.R. Weinberg and D.D. Berg, “Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby”, New England Journal of Medicine 333, 1517 – 1521, 1995.

Hodgen et al. paper on different survival times of X and Y sperm:

Q. Van Dyk, M. C. Mahony and G. D. Hodgen, “Differential binding of X- and Y-chromosome-bearing human spermatozoa to zona pellucida in vitro”, Andrologia, Volume 33, Issue 4, Page 199, July 2001.

Johns Hopkins University meta-analysis of six NFP studies:

R. H. Gray, “Natural family planning and sex selection: fact or fiction?”, American  Journal of Obstetrics and Gynecology 1991 Dec; 165(6 Pt 2):1982-4.

University of Washington School of Medicine review and assessment:

P. W. Zarutskie, C. H. Muller, M. Magone and M. R. Soules, “The clinical relevance of sex selection techniques”, Fertility and Sterility 1989 Dec; 52(6):891-905.


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4 Responses to “Fetal sex preselection – illustrated”

  1. Fetal sex pre-selection – the fundamentals | bioZhena's Weblog Says:

    […] For more about fetal sex pre-selection, see “Fetal Sex Preselection – Illustrated” at https://biozhena.wordpress.com/2007/12/03/fetal-sex-preselection-%E2%80%93-illustrated/ […]

  2. Regarding fetal sex preselection | bioZhena's Weblog Says:

    […] may well be a burning question in numerous minds) with the illustrations and explanations. That is: Fetal sex preselection – illustrated […]

  3. The Ovulona is not another ovulation kit, my dear | bioZhena's Weblog Says:

    […] more on the foundation of this belief (i.e. for the working hypothesis), see https://biozhena.wordpress.com/2007/12/03/fetal-sex-preselection-%E2%80%93-illustrated/ – and if you do, then do not overlook the slide The three-day fertile window how-to . In this […]

  4. The Ovulona™ | bioZhena's Weblog Says:

    […] The three-day fertile window how-to (to exit the slide, just click on it). In this slide, we show the outcome of a France et al. study of fetal gender pre-selection superimposed on the menstrual cyclic profile […]

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