There has been insufficient study of this phenomenon that started in 1967, in the sense that to attribute the appearance of abandoned children to the prohibition of abortion would imply that their mothers would have obviously resorted to abortion to avoid giving birth to unwanted children they would later abandon.
For some mothers the resorting to abortion is considered a rather responsible attitude to reproduction, within certain parameters (in terms of values of the respective timeframe). Based on such logic, however, it is difficult to believe that a sub-category of women came into being who replaced fertility control by abortion with child abandonment from this category of mothers who use abortion to limit fertility.
While one can presently find numerous similarities between abandonment and abortion, their association in 1967 was hardly acceptable in terms of the values of those times, especially as concerns abortion.
Therefore one feels certain about the undoubted existence of other determinants or phenomena that strangely combined with the pro-natalist decree to generate that particular segment of the population that resorted to abortion. These may include the displacement of large segments of the population due to industrialization, the failure to morally condemn such behavior, or the encouragement, for one reason or another, of the breach between mother and child, that overlapped and crossed to produce such a brutal social level effect on children, especially in terms of unwanted ones.