Fetal sex pre-selection – the fundamentals

For this and the various related concepts and terms, see the Alphabet of bioZhena at


Fetal sex pre-selection:

Here is the underlying principle: Out of the 46 chromosomes (23 pairs), the last pair is the sex chromosome. It is of the XX type in the female and XY type in the male. The ovum (egg) has X type chromosomes only, while 50% of the sperm have X chromosomes and 50% have Y chromosomes. If an X sperm fertilizes the egg, this results in an XX combination, which is a female offspring. If a Y sperm fertilizes the egg, the result is an XY combination and a male child.

According to http://www.fertility-docs.com/fertility_gender.phtml , “the selection of gender has been a quest of couples for as far back as recorded history allows. Early drawings from prehistoric times suggest that sex selection efforts were being investigated by our earliest ancestors. Later history shows intense interest in sex selection by early Asian (Chinese), Egyptian and Greek cultures. This is followed by documented scientific efforts beginning in the 1600s to sway the chances of achieving a pregnancy by a variety of methods…” QUOTE UNQUOTE

Two approaches to sex selection have been demonstrated in the current scientific literature. One approach employs the tools and methods of assisted reproductive technologies (ARTs), manipulating the genetic material of the sperm prior to artificial insemination, so as to facilitate fertilization by the selected one of the two genders of the spermatozoa. The other approach attempts to enhance the probability of conceiving the desired gender by appropriate timing of the conception event with respect to ovulation. This is a highly controversial subject despite the fact that a substantial body of work on it has been published.

Thus, a 2001 publication by respected experts from a premier infertility treatment institute (G.Hodgen et al., see below) has put forward evidence that male spermatozoa (Y-chromosome-bearing sperm) live longer than female spermatozoa (X-chromosome-bearing).

This is consistent with earlier findings by Auckland, New Zealand researchers that boys tend to be conceived earlier in the fertile period than girls (the earlier conception requires a longer lifetime of the sperm). This was discussed in our two previous posts: /2007/12/02/regarding-fetal-sex-preselection/ and /2007/12/03/fetal-sex-preselection-illustrated/ .

A 1991 Johns Hopkins University meta-analysis of six NFP studies concluded that the data showed “a statistically significant lower proportion of male births among conceptions that occur during the most fertile time of the cycle”, meaning near ovulation. Indeed, the Auckland study by Professor John France’s group found that 65% of male infants were conceived 2 to 5 days before ovulation while “71% of the born girls were conceived from intercourse timed between 1 day before to 1 day after the estimated time of ovulation”. This was based on 55 births. See the referenced previous posts.


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

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

2) We might refer to the second, the correct-timing, approach to fetal sex pre-selection as eukairosic. This [Eukairosic™] with reference to http://www.perseus.tufts.edu/cgi-bin/lexindex?lookup=kairo/s〈=Greek

kairos III. more freq. of Time, exact or critical time, season, opportunity… … …

3)  France et al. paper with data on fetal sex pre-selection by timing intercourse:

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.

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/


The organism that develops from the embryo at the end of about seven weeks of pregnancy and receives nourishment through the placenta. Fetus, plural fetuses:

1. The unborn young of a viviparous vertebrate having a basic structural resemblance to the adult animal. Viviparous: Giving birth to living offspring that develop within the mother’s body. Most mammals and some other animals are viviparous. Vertebrates have a backbone or spinal column.

2. In humans, the unborn young from the end of the eighth week after conception to the moment of birth, as distinguished from the earlier embryo. [From Latin fetus, offspring.]


The embryo is the organism that develops from the pre-embryo, and begins to share the woman’s blood supply about nine days after fertilization. Approximately one-half of all human embryos are abnormal [ http://www.columbialabs.com/html/crinwom/infertility/fertilization.htm ]. QUOTE: “There is fortuitously a biologically based selection bias against abnormal human embryos. A signal is obviously recognized by the mother, which helps explain why so many embryos fail to implant. An abnormal embryo that manages to implant is often miscarried in the first 10 weeks of pregnancy. Early miscarriages are almost always the result of abnormal development of the fetus. This is why progesterone is not usually recommended for threatened abortion. It is only if the physician can confirm, using ultrasound, that the fetus is viable, will he prescribe progesterone to help maintain the pregnancy.”

Veterinary fetal sex pre-selection:

A similarly high level of interest in embryo sexing (fetal sex pre-selection, or sex ratio) exists in the livestock industries, and researchers have experimented with the timing of insemination method. A tool such as the bioZhena Corporation’s BioMeter is indispensable for this approach to embryo sexing, because of the required accuracy and precision of the timing. The controversy in the veterinary literature is a clear evidence that timing the insemination merely with respect to estrus is not good enough. The timing must be with respect to ovulation. The BioMeter, which detects ovulation as well as anticipating it, should make it possible to investigate questions such as whether different species have different lifetimes of the sperm. It should be possible to establish what kind of a distribution of sperm lifetimes there may be within a species. (See also under Timing of insemination.)

The 2001 book Biotechnology in Animal Husbandry (R. Renaville & A. Burney, editors, Kluwer Academic Publishers) has a chapter on Sex Preselection in Mammals. The abstract states: Since a long time, sex preselection has been a goal of the dairy and meat industry to increase the rate of response to selection, to reduce the cost of progeny [offspring or descendants] testing for elite males, and to produce desired specialized and genetically superior offspring. The authors write: In animal husbandry, pre-selection of sex prior to conception will dramatically impact a farmer’s productivity and income, because in each of the chosen target industries there is a strong preference for one sex over the other. For example, the dairy industry must have females to produce milk whereas the beef industry prefers males for their higher quality and lower cost of production. Sex pre-selection is one of the most sought after biotechnologies of all times.

In a section on Factors Affecting Sex Ratio, the experts write: Considerable folklore particularly in humans has arisen regarding preconception methods to manipulate animal sex ratio. The authors point out that conventional wisdom holds that steroid hormones play no role in sex predetermination in mammals, and it is only after gonadal differentiation that steroids sculpt the characteristics, which distinguish males from females. They also write that, for a number of years, the time of insemination or mating during estrus has been believed to influence the sex ratio of offspring, and they review various conflicting reports in several animal species. One kind of these results, in cows, indicates that the sex ratio may be affected by the maturational state of the oocyte [egg] at the time of insemination (yielding sex ratio 0.7 when inseminated immediately after, and 2.5 when inseminated 8 hours after polar body extrusion, which basically refers to ovulation timing). In their Conclusion, the experts again point out that “economics dictate that livestock producers are under increasing pressure to produce a given number of progeny of the desired sex.”

The results of sex pre-selection experiments depend on the state of the ovulating egg and of the sperm. This may depend on whether a given father belongs into a sub-population of males with long or short sperm lifespan. Whether there is such a thing as this kind of categorization within a species can only be established by means of a tool such as the Ovulona/BioMeter.

This holds for all species, including Homo Sapiens, of course, and public health statistics make such categorization actually quite likely. In the U.S., the sex ratio (number of males born per 1000 females) has declined from 1.052 in 1983 to 1.049 in 1999, having been as low as 1.047 twice in the late nineties. Interestingly, this decline is evidently due to the decline in the white race (from 1.057 to 1.052, through as low as 1.049) whereas for the black race the sex ratio has actually increased over those years (from 1.028 to 1.031, through as high as 1.036) [web reference: http://www.infoplease.com/ipa/A0005083.html ].

All this is suggestive of a likely strong reason why people will want to use the bioZhena [eukairosic] products, and the application will not even need to be advertised.


Tags: , , , , , , , , , , , , , , , , , , , ,

5 Responses to “Fetal sex pre-selection – the fundamentals”

  1. nick Says:

    HmCzOs hi! hice site!

  2. Nagoescamsfata Says:

    Tahnks for posting

  3. Gray Moon Gallery Says:

    Phalluzoïde ou L’Origine du Sexe is an acrylic on canvas painted by Jan Theuninck in 1999. (Dimensions : 100 cm x 70 cm)
    The painting depicts an external sexual organ of a man with inside a spermatozoon which determines the sex of the future child : carrying a Y chromosome it will lead to a male (XY), carrying an X chromosome
    it will lead to a female (XX).
    Phalluzoïde (Please do not touch, lick, stroke or mount this artwork) by Jan Theuninck, 1999

  4. data selection Says:

    data selection…

    […]Fetal sex pre-selection – the fundamentals « bioZhena’s Weblog[…]…

  5. click the following internet page Says:

    click the following internet page

    Fetal sex pre-selection – the fundamentals | bioZhena’s Weblog

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: