Table 1 Maternal outcome measures

 1.1 Depressive symptoms

x

x

x

x

Edinburgh Postnatal Depression

Scale (EPDS)

10-item validated questionnaire to screen for depressive symptoms in a post-partum setting [53].

  1.2 Anxiety

x

x

x

x

State-Trait Anxiety Inventory (STAI)

The STAI is a 40-item validated questionnaire to screen for anxiety [54].

  1.3 Stress

x

x

x

x

Alledaagse Problemen Lijst (APL)

The APL is a 49-item validated questionnaire to assess the occurrence and intensity of daily hassles [55].

  1.4 Traumatic Stress following child birth

x

x

x

x

Traumatic Event Scale-B (TES-B)

The TES-B is a 35-item validated questionnaire to examine traumatic stress after giving birth to a child [56].

  1.5 Sleep quality

x

x

x

x

Adjusted version of the Karolinska Sleep Diary (KSD) & Pittsburgh Sleep Quality Index (PSQI)

Every morning, for three consecutive days, the mother will fill in the KSD starting at week two, five and twelve [57]. In addition, questions related to daytime sleep and reasons for wakening will be included. At twelve weeks and one year, the mother will fill in de PSQI [58]. The PSQI is a 19-item validated questionnaire to examine sleep quality and disturbances in reference to their sleep during the past month.

  2.1 Physical recovery related to the delivery

x

x

x

x

Maternity carer logbook & Multidimensional Fatigue Inventory (MFI) & Bodily Pain subscale of the Short-Form Health Survey (SF-36)

The maternal physical recovery logbook of the maternity carer from the first week after birth will be copied at the second home visit. The MFI is a 20-item validated questionnaire to examine fatigue [59]. The two-item subscale of the SF-36 will be used to examine bodily pain [60].

  2.2 Health

x

x

x

Health interview & questionnaire

A maternal health interview, based on the infant health interview [61], will be performed during the second home visit. During the follow-up assessment the mother will fill out health questionnaires, based on the infant health interview [61].

  2.3 Breastfeeding

x(w1–12)

x

Weekly logbook

The mother will fill out a weekly logbook including the estimated times of breastfeeding, expressed breastmilk feeding, and formula feeding to examine breastmilk initiation, exclusivity, frequency and duration. At one year of age, mothers will note the number of months the infant was breastfed and she will note the current feeding status.

  2.4 Physiological stress

x

Hair cortisol

Hair analyses will be used to show the activity of the HPA axis over longer periods of time. A strand of hair will be cut from the scalp.

  3.1 Mother-infant bond

x

x

x

x

Maternal Postnatal Attachment Scale (MPAS)

The MPAS is a 19-item validated questionnaire to assess current maternal attitudes, thoughts, and feelings towards the child [62].

  3.2 Quality of maternal caregiving behavior (sensitivity)

x

Ainsworth Sensitivity Scales

An infant bathing session during the home visit on week five will be videotaped. After, reliable observers, blinded for group allocation, will observe maternal sensitivity [63].

  3.3 Quality of maternal caregiving behavior (synchrony)

x

Saliva cortisol

Synchrony will be measured with saliva samples of both the mother and infant before and after the bathing session (undressing, bathing and dressing). Samples will be collected right before undressing (baseline, T1), and 25 (stress, T2) and 40 (recovery, T3) minutes after the infant is taken out of bath [64]. Saliva will be collected in tubes for the mother and with eye sponges for the child [65]. Cortisol synchrony consists of the within mother-infant dyad cortisol associations (i.e. mother cortisol predicting infant cortisol, infant cortisol predicting mother cortisol). Cortisol synchrony will be examined for every saliva sample (pre-stress, peak-stress, recovery), for total stress cortisol concentrations (Area Under the Curve (AUC)), and cortisol recovery (recovery – pre-stress).

 Oxytocin concentrations

x

Saliva oxytocin

Maternal oxytocin concentrations during the bathing session will be measured in saliva at the same time points as cortisol. Saliva will be collected in tubes.