Smart Stork claim to be able to help couples select the gender of their future child:

Our success rate in gender selection? Is still over 95%!

Their technique relies of biorhythms:

Smart Storks unique gender selection program, is based primarily on a womans biorhythm cycle and the alternating pH of acidic and alkaline fractions within her reproductive tract, these fluctuations directly affect the gender baby that can be conceived at the time of ovulation. The biorhythm theory is a theory based on the fact that every person, from the moment of birth, is ruled by their biorhythms or circadian rhythms. It rules the balance of our sleep/awake body clock and is the basis of our hormone secretions.

Our research focused on the impact of the women’s biorhythm cycles and her hormone production, the alternating pH within the follicular fluid and how that was a major factor in determining the baby’s gender at the time of ovulation.

The idea that a baby's gender is determined at ovulation, rather than conception, is a new one to me.

Their claims are (allegedly) supported by dozens of references.

Can techniques such as these be used with 95% reliability to select the gender of a yet-to-be-conceived child?

  • Note: this question was asked as part of the "topic of the week" initiative to raise our questions per day stat. Please contribute some great questions!
    – Oddthinking
    Feb 15, 2012 at 13:02
  • 2
    I think that the idea of The idea that a baby's gender is determined at ovulation, rather than conception, is a new one to me. has to do with sperm motility, and where fertilization may happen as a result of ovulation as opposed to the ova itself.
    – JasonR
    Feb 15, 2012 at 15:32
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    @Brightblades: Oh! So it accidentally ties into my other question about gender-selection. I didn't intend/expect that.
    – Oddthinking
    Feb 15, 2012 at 16:26
  • Regarding biorhythm cycle, scientists believe that the idea has no more predictive power than chance and consider the concept an example of pseudoscience. An examination of some 134 biorhythm studies found that the theory is not valid-amsciepub.com/doi/abs/10.2466/pr0.1998.83.1.19?journalCode=pr0 and also read more here-skepdic.com/biorhyth.html. Aug 7, 2015 at 6:03
  • @pericles316: If that is an answer, please use the answer box.
    – Oddthinking
    Aug 7, 2015 at 8:00

1 Answer 1


The woman's biorhythm cycle which is the primary basis for Smart Storks unique gender selection program is described by scientists to be pseudoscience and also an examination of 134 biorhythm studies in 1998 found that the theory is not valid.

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