The Northern Babies Longitudinal Study

Aims

The present study has three broad aims:

1. Examine key pre- and postnatal predictors related to parental functioning: a) parental depression, anxiety, and stress, b) parental reflective functioning in relation to the infant, and c) parent-infant attachment style.
2. Examine key pre- and postnatal predictors related to interaction and developmental problems in the child: a) difficulties in parent-infant interaction in the first 4 months post-delivery, and b) infant's cognitive, communicative and motor development, signs of sustained withdrawal behaviour, and heart-rate variability at 6 months post-delivery.
3. Evaluate the effectiveness of the NBO as a universal preventive intervention delivered in routine practice as compared to standard care, on:

• Parental outcomes (depressive symptoms, parenting stress, reflective functioning, attachment to the infant),
• Relational outcomes (emotional availability in parent-child interaction), and
• Infant outcomes (cognitive, communicative and motor development at 6 months post-delivery, heart-rate variability).

Predictor variables include some well-known vulnerability factors for developing PPD (e.g., depression symptoms in pregnancy, adult attachment style, relationship satisfaction and life stress), but the main focus in the observational part of the research project is on cognitive vulnerability factors such as early maladaptive schemas, repetitive negative thinking, rumination, implicit attitudes and cognitive processing of emotionally valenced infant facial information.

Study design This is a longitudinal observational study with an intervention. The observational part of the study will use a prospective cohort design. The effect of the intervention will be evaluated using a non-randomized cluster controlled design, since neither cluster nor individual randomization is feasible in this routine practice setting. An intervention group receiving NBO (families belonging to two well-baby clinics in Tromsø municipality) will be compared with a control group (families at the remaining four well-baby clinics in Tromsø) receiving care as usual.

Recruitment All pregnant women and expecting fathers who speak Norwegian are eligible for inclusion in the study. Between autumn 2015 and autumn 2018 approximately 200 families will be recruited by midwifes and by general practitioners (GPs) in the municipality of Tromsø, which is the 9th largest municipality in Norway (~73000 inhabitants; 78). There are approximately 1000 births a year in Tromsø municipality. Based on the experiences from a comparable study, "Little in Norway" (79), the recruitment of 200 families within the project period is considered feasible.

The participants will be recruited in (approximately) week 16 of gestation. At recruitment, women will be given written information about the study and a flyer with an inquiry to be contacted by the research team. If the child's father is not present, the mother is encouraged to inform him about the study. The health worker informs the research team who contacts the women to plan a meeting with them and their partners, preferable between week 16 and 22 of gestation. In this meeting, the prospective parents are given detailed information about the study and are invited to sign an informed consent to participate. In addition, at 4 months post-delivery the parents will be asked to sign an informed consent to obtain birth related information from the birth record.

Power calculations/statistical analysis The sample size is calculated on the basis of differences between intervention group and standard care group on the Edinburgh Postnatal Depression Scale (EPDS) maternal score, the Parenting Stress Index (PSI-PD), the Parental Reflective Functioning Scale (PRFQ) and the Maternal Postnatal Attachment Scale (MPAS) 6 weeks post-delivery. Based on the pilotstudy by Nugent et al. (69) and some regression to the mean, we expect a small to medium effect size (f2 = .07). A MANOVA with the four aforementioned outcome variables can detect a difference between the groups with a power of .80 given a group sizes of N = 176. With an estimated dropout of 10 %, a group size of 200 will be recruited. The estimation is based on an α-level of .05.

Procedure For the observational part of the study, assessments will be performed at six time points (see Table 1): During gestational week 16 - 22 (Step 1), 24 - 30 (Step 2) and 31 (Step 3), and at 6 weeks (Step 4), 4 months (Step 5) and 6 months (Step 6) post-delivery. For the intervention study, pre-intervention measures will be collected at Step 3, post-intervention measures at Step 4 and follow-up measures at Step 5 and 6. Since the families will receive the first NBO already two-days post-delivery, no pre-test assessment can be obtained for the interaction and infant measures. Hence, analyses of intervention effects will be based on differences between groups at 4 and 6 months post-delivery controlling for relevant covariates. The data is collected using online questionnaires, computerized cognitive tests, video-filmed observations of mother-infant interactions, and a standardised test of the child's cognitive, communicative and motor development (Bayley Scales of Infant and Toddler Development; 80).