Maternal Mental Health Intervention (MaMHI) Study: A Combined Non-inferiority and Superiority Randomized Controlled Trial Comparing the Clinical and Cost-effectiveness of an Online Self-help Intervention and a Brief Face-to-face Intervention Versus Usual Care in Mothers at Moderate Risk for Perinatal Depression Identified by a Concentration-of-risk Prediction Approach.

Introduction The perinatal period, encompassing pregnancy and the first year postpartum (O'Hara & Wisner, 2014), represents a time of significant physiological, psychological and social change, necessitating considerable adaptation by expectant parents (Milgrom & Gemmill, 2015). This transitional phase is characterized by a coexistence of intense positive emotions-such as joy, hope, and excitement-and challenging negative emotions, including insecurity, anxiety and depression. As a result, both the transition to parenthood and the early stages of parenting are associated with increased vulnerability to emotional difficulties.

Mental health problems are highly prevalent in the perinatal period, affecting approximately one in five expectant or new mothers (Van Damme et al., 2018). Among these, perinatal depression (PD)-which includes both minor and major depressive episodes-is one of the most common complications during pregnancy and postpartum (Wisner et al., 2013). The point prevalence of major depressive disorder during pregnancy ranges from 3.1% to 4.9%, increasing to approximately 5% in the first three months postpartum. Minor depression affects an estimated 11% of pregnant women and 13% of women in the first three months after childbirth. The period prevalence of any depression during pregnancy and the first three postpartum months is estimated at 18.4% and 19.2%, respectively, with 12.7% and 7.1% meeting criteria for major depression during those timeframes (Gavin et al., 2005). Notably, one-third of postpartum depression cases begin during pregnancy, and 27% have onset prior to pregnancy (Wisner et al., 2013). Depression during the second and third trimesters increases the likelihood of postpartum depression by factors of 3.2 and 6.6, respectively (Heron et al., 2004). Mental health disturbances during pregnancy are therefore strong predictors of postpartum mental health status (Robertson et al., 2004).

Although most women recover from postnatal depression within a few months, approximately 30% remain clinically depressed beyond the first postpartum year (Goodman, 2004), and 40% may develop a chronic depressive disorder (Vliegen et al., 2014).

The consequences of perinatal depression extend beyond the individual, significantly affecting the mother-infant relationship and the child's socio-emotional development (Atif et al., 2015). For instance, the perinatal period is critical for the establishment of a secure attachment, which is fundamental to a mother's capacity to recognize and respond to her infant's emotional cues (Rosenboom, 2018). Maternal mental health issues may interfere with mothers' emotional availability and responsiveness, which may in turn compromise children's development.

Consistent with these assumptions, epidemiological and longitudinal studies have demonstrated that children of parents with depression have significantly elevated risks of developing depression themselves (Rosenboom, 2018). For example, Weissman et al. (2006) found that offspring of depressed parents were three to four times more likely to develop depression compared to children of non-depressed parents, with up to 50% affected by age 20.