Updated: Nov 5, 2021
Eugen Jonas became known for an unusual family planning method  that he developed as a young doctor in the early 1950s on the basis of astrological traditions and that met with great resistance from his medical colleagues. As part of para- scientific research projects in the 1960s in what was then the Eastern Bloc, he was able to make his method known through numerous lectures.  Published was the method as a moon phase angle theory. According to this theory, an additional ovulation can be triggered in a woman if the current moon phasecoincides with that which existed at the time of the woman's birth. As a result, many women in their childbearing phase of life react synchronously to the monthly repetition of the current moon phase angle with an increased willingness to conceive, which is repeated month after month.
According to Jonas, the sex of offspring is said to be 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 in the West is usually referred to as the "cosmobiological method" or "cosmobiological conception planning", offers 98% security in the choice of gender, provided that the time of conception is chosen so that the moon is in the middle of the desired eclipticalSegment (male or female) is when the most fertile phase of a woman is predominant. The moon changes its orbit approximately every 2 ½ days 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 with the fact that in these cases the moon would have been exactly between two female and male segments at the time of conception.
The Astra research center in Nitra carried out series examinations and statistical surveys  . The external scientific patronage of the scientific activity of the Astra Center was held by the subsection of Biosociology (Astrobiology) of the Integral Anthropology Section of the Czechoslovak Sociological Society in the Academy of Sciences in Prague.
The aim of the two-year investigations was to check the thesis that, in addition to the known period cycle, there is another individual cycle that is related to the phases of the moon. The earlier work and some of his colleagues (Kurt Rechnitz, Jiri Malek) that had been undertaken since 1956 were evaluated and further studies were developed. Kurt Rechnitz combined the Jonas method with the established menstrual cycle to create a more complex method called the “Jonas Reichnitz method”, which is used both for contraception and for gender planning  .
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 .