I don't mean that the nursing period is so much a differentiating factor for the outcome, but rather that if the parents chose to breastfeed, that is one and ab

I don't mean that the nursing period is so much a differentiating factor for the outcome, but rather that if the parents chose to breastfeed, that is one and about the only biologically differentiated role between a mother and a father, thus needs to be accounted for in some way. Ideally men should take more of other child caring burdens during the breastfeeding, but that depends on various other practical factors, so I wouldn't call men up for failing to do that.