The first 3 months of life is a period of rapid developmental transition, as the infants behaviour shift from intrauterine to extrauterine regulation. The newborn infant faces a series of hierarchically organised developmental challenges as he attempts to adapt to his new, extrauterine world. This includes the infants’ capacity first to regulate his autonomic system, then his motor behaviour, his state regulation, and finally his affective interactive behaviour.
From a developmental perspective, this period is characterised by changes that involve major reorientations in person-environment relations and marks an important transition period in the infants’ behavioural development promoted by a critical period of brain development.
The period that follows answers to a different developmental agenda whereby the infant has already accomplished many of the developmental challenges and adaptation of the first months, and the environmental influence is more integrated.
From the parents’ perspective, the first 3 months is possibly the most sensitive period in the parent-infant adaptation, as parents attempt to establish a relationship with their new infant.
This transition to parenthood in which the parents have a heightened sensitivity to their infant is the most effective period to foster the parent-infant relationship and promote a goodness of fit between infants and parents.