The prenatal Epoch idea is so well known that astrology software such as Solar Fire allows the user to calculate their prenatal Epoch. The idea of the prenatal Epoch is also useful because it is often decisive in chart rectification
*****EDIT: I noticed that Solar Fire calculated the prenatal Epoch when I purchased my own personal a copy of Solar Fire bought directly from the company and for which I paid the full original price which was not cheap!
HOWEVER my software copy of Solar Fire is currently installed on an older computer that is no longer in use due to my having upgraded with new computer equipment.
FURTHERMORE I have no interest in using Solar Fire because I purchased and installed Placidus 7 and Porphyrius Magus obtained from Rumen Kolev at Babylonian Astrology website http://www.babylonianastrology.com/
NEVERTHELESS I retain the disc I purchased directly from Solar Fire i.e. it is not a second hand disc so I paid full price. I keep that disc for several reasons, one of which is that I may need it. I prefer to calculate the prenatal Epoch without the use of software since I have personally found that is the more accurate method