There are several reasons to believe that some mothers can turn incompatible with their male offspring after they have given birth to several boys. Some women might even be incompatible by the first conception. The whole picture has perhaps something in common with the histo-incompatibility. Sex-linked incompatibility is well known to exist, and in the phenomenon of Eichwald and Silmser. Then, the Takahashi phenomenon might be interpreted as a sign of moderation of an incompatibility reaction.