Parents’ capacity to represent and sensitively respond to their children as individuals, is a particularly pertinent ability during infancy. This thesis contributes to theoretical understanding of the nature of parental sensitivity during infancy. In particular, it examined whether parental mind-mindedness and coherence, dimensions theoretically related to sensitivity, are (i) measurable during pregnancy, (ii) conceptually distinct, and (iii) meaningfully associated with observed sensitivity. Results from two studies are presented. The first, a prospective longitudinal study, involved interviews with and observations of 201 first-time parents during late pregnancy and at 4 and 14 months postpartum. Drawing on this data, I established that both expectant mothers and fathers can construct mind-minded and coherent descriptions of their unborn infants during pregnancy. However, there was no evidence that these prenatal constructs had a direct or indirect effect on parents’ sensitivity during infancy. These results were added to the second meta-analytic study that showed expectant mothers’ (but not fathers’) thoughts and feelings about their unborn infant were related to their observed parenting in the postnatal period. In line with the gendered meta-analytic results, further differences emerged between mothers’ and fathers’ talk and behaviour within the prospective longitudinal study. Specifically, mind-mindedness was more stable than sensitivity for mothers whilst the reverse was evident for fathers. Compared with mothers, fathers’ talk and behaviour was more susceptible to influence from other members of the family system. Couple relationship quality influenced both fathers’ prenatal coherence and gains in their mind-mindedness over time. Infant affective responses were also important for fathers’ mind-mindedness, whilst maternal parental efficacy alongside infants’ receptive vocabulary were associated with fathers’ sensitivity. Unexpectedly, infant gender was an important influence on parents’ behaviour: mothers’ sensitivity at 4 months appeared to stimulate fathers’ sensitivity towards their daughters at 14 months. By following both mothers and fathers and in line with family systems theory, assessing whether partners contribute to the emergence of their co-parents’ sensitivity, this thesis provides a rich portrayal of the transition to parenthood in the 21st century.