By: Aronson, Stacy Rosenkrantz, and Aletha C. Huston.
Using data from US women who recently gave birth, these researchers find that on average married mothers report more financial resources and have about 2 more years of education than either single or cohabiting mothers. They also report greater amounts of love and/or intimacy and less ambivalence and/or conflict in their relationship with their partners than cohabiting mothers.
Mother-infant relationship in single, cohabiting, and married families: A case for marriage? Journal of Family Psychology 18 (1): 5-18.