According to a recent study in the Journal of Family Psychology, couples who cohabited prior to engagement reported "lower marital satisfaction, dedication, and confidence as well as more negative communication and greater potential for divorce."  The study was done on individuals 18-34 who had been married for ten years or less.  This group of dissatisfied individuals consisted of a whopping 43.1% of the participants. Moreover, the study purports that in many cases, cohabiting couples find themselves getting married for reasons other than love.  It seems like a no-brainer that couples would then report lower satisfaction once married.

Throw in a kid and the situation only gets more complicated, for the woman and child, at least.

In another study also published in the Journal of Family Psychology, researchers studied the effects of cohabitation on the relationship between parent and child.  In this particular study, however, researchers opted to study unmarried "stably" cohabiting couples compared to married couples.

In such cases they found that the mothers "reported more depressive symptoms."  Furthermore, they were "less sensitive" to their children than their married counterparts particularly because they found that "cohabiting couple relationships were characterized by more ambivalence and conflict."  In essence, without that stability and security that marriage promises, the women and children were more likely to be impacted negatively.