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Updated: Jun 30, 2022

Is it possible to predict the gender of a baby from the Moon? How can it be predetermined by choosing the hour of conception according to the Moon’s astrological sign? And can women really rely on astrological calculations when choosing the sex of a baby? The answer is YES!!!

Sex selection has been known since ancient times. Many families decide to conceive a child of a specific gender as a result of unsuccessful attempts to have a son or daughter.

Dr. Jonas’ three fundamental rules

Rule 1.

The time of the highest woman's fertility coincides with the recurrence of the angle of the sun and the moon that occurred at the woman's own birth. For example, if the woman herself was born during a New Moon, her highest fertility days would be during the New Moon each month. This may even fall on days of her menstruation.

Rule 2.

The gender of the baby to be conceived depends only on the position of the Moon at conception. A lunar cycle lies at the basis of sex determination. Jonas believed that as the Moon passes through the different signs of the zodiac, the alkalinity of the womb is changing for acidity and vice versa affecting the sedimentation of the sperm.

In Astrology, there are 12 zodiac signs. The date and time of the child’s conception must fall under a ‘male' or 'female' sign.

The female signs include:

  • Virgin,

  • Taurus,

  • Scorpion,

  • Cancer,

  • Pisces,

  • Aries.

The male signs include:

  • Leo,

  • Aries,

  • Sagittarius,

  • Gemini,

  • Aquarius,

  • Libra.

If a child was conceived when the Moon was moving through the 'male' sign, the baby would most likely be a boy. If the child was conceived when the Moon was moving through the 'female' sign, then the baby will most likely be a girl.

If a woman has a regular menstruation cycle, the probability of conceiving a boy or girl is every 2-3 days.

During his studies, Jonas’ found that all women have two monthly ovulation cycles, lunar and menstrual. The thing is the menstrual cycle does not sync with the lunar cycle. The present day studies show that 40% of women have the clear biological potential to produce more than one egg in one month which means that ovulation during menstrual cycle can be affected not only by hormonal changes but the Moon. On the other side, the lunar cycle is always constant occurring 12-13 times a year which may be helpful in determining the sex of baby.

Who Was Dr. Jonas?

Eugen Jonas became known for an unusual family planning method that he developed as a young doctor in the early 1950's on the basis of astrological traditions and thus met with great resistance from his medical colleagues. As part of para- scientific research projects in the 1960's in what was then the Eastern Bloc, he was able to make his method known through numerous lectures.

Published was the method of the moon phase angle theory.

Jonas found that the sex of the offspring is related to certain phases of the moon at the time of conception. The astrological sign in which the moon is at the time of one's own conception should be decisive for the gender of the child. According to Jonas, his method, which is usually referred to as the "cosmobiological method" or "cosmobiological conception planning" in the West, offers a 98% certainty in the natural sex selection of gender, provided that the time of conception is chosen so that the moon is in the middle of the desired ecliptical Segment (male or female) is when the most fertile phase of a woman is predominant.

The moon changes its orbit approximately every 48 hours, between a female and a male segment. The decisive factor for the sex of the child, however, is the exact time of fertilization of the female egg. Jonas explains the fact that there are twins of different sexes and the reasoning for these cases is the moon would have been exactly between the female and male segments at the time of conception.

According to Jonas, the moment of birth (monophase angle at the time of birth) would have a biologically determinant meaning for the future fertility cycle, which belongs exclusively to the theoretical foundations in astrology .

Dr. Jonas discovered that under certain circumstances the bio-chemical environment of the endometrium is subject to certain periodic variations and that these in turn lead to sedimentation of the sperm. His method shows that there are some days in woman's fertility cycle where she can conceive a BOY only and days where only a GIRL can be conceived.

In the mid-1960's, Dr. Jonas's theories were first put into practice. A local newspaper, The Voice of Nitra, began to inform the public about the existence of the Natural Conception Control and invited volunteer couples to participate and help the research by trying the Dr. Eugen Jonas Method. By 1965, a sufficient number of volunteers became available, and Dr. Jonas's calendars were published with instructions provided in Czech, Slovak and Hungarian languages.


The infertile day tests were first performed with the help of married couples who wanted to have children, but were willing to test for the infertile days. Within six months sufficient material became available and within a year the research was complete. The results were truly satisfying, with a 97.8% accuracy. Those same couples then received a new calendar for the following year where the fertile days as well as the gender were marked, so that the couples could choose the gender of their child. Dr. Jonas was invited to prove his theories at the Bratislava Clinic of Gynaecology, by Dr. Aurel Hudcovic. Here, he worked out individual calendars for 8,000 women who wanted to have only male babies. Ninety-nine percent (99%) of them fulfilled their dream some nine months later! Then new trials were started with couples who produce only non-viable foetuses. Using the method, the couples chose a date for the conception of a viable child. The results were excellent: 98% reliability was again achieved. Finally, the turn came for women who could not become pregnant at all. For them, a calculation was made for optimal days of conception for one year in advance. In this case, no consideration had been made for the gender of the child, as the conception itself was most important. New series of tests began in July 1969 and by July 1970, applications from another 30,000 married couples from Czechoslovakia only were processed. A commission from Budapest evaluated the results and the success rate was again 98%. Dr. Jonas then travelled abroad explaining to gynaecologists, physicists and doctors the efficacy of his theories. He has also presented his calculations, tables, case histories and the results of his thesis to both the Hungarian and Czechoslovak Academy of Sciences. A committee of gynaecologists then queried Dr. Jonas, if his technique could be worked backwards. They challenged him to predict the sex of the child, by telling him the approximate date of the impregnation. Once again, Dr. Jonas stood up to the occasion and achieved 87% accuracy off the top of his head!


  • Dr. Eugen Jonas Method® is 98% accurate.

  • Baby's sex determination is 98% predictable.

  • 85% of the pregnancies occurred on Dr. Jonas's calculated date.

  • In the primary or secondary infertile applicants, 2/3 became pregnant within the first year of using this method, 1/3 within the second year.

Dr. E. Jonas's dream was to make the secrets of his painstaking discoveries available to each and every parent. With his hard work and research, his dream has come true.

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