The dramatic drop by the six - month mark reflects
the interplay of a number of factors: struggles with the mechanics at the beginning; the need to attend to older children; the difficulties of maintaining breast - feeding upon the return to work; the embarrassment of baring a breast in public places.
It is thought to be due to a complex
interplay between polygenic and various environmental risk
factors, although recent reports on genomic copy
number variations suggest that a fraction
of the cases could result from variably penetrant de novo variants.