Table 3.
Secondary outcomes
| Domain | Description | Tool/analysis | Time point |
| Respiration | Need for surfactant. Time on invasive ventilation, CPAP and nasal cannula. | Medical records | During hospital stay |
| HRV | HRV as a proxy for autonomic stability | Propaq (Zoll, USA) | During intervention, at 48 to 72 hours, discharge and 3 to 4 months |
| Thermal control | Infant and parent axillary temperature | During intervention | |
| Infection | Clinical sepsis, positive blood cultures and days on antibiotics | Medical records | During hospital stay |
| Skin-to-skin contact | Skin-to-skin contact duration per day with a parent | Parental diaries | During hospital stay |
| Breastfeeding and growth | Postnatal age at first feed, time to full enteral feeds and time to full non-gavage feeds. Breastfeeding initiation, and duration and maternal self-efficacy. Breastfeeding status. Weight trajectory. | IBS51
BSES52 Medical records |
During hospital stay, at discharge, at term, 3 to 4, and 12 months |
| Epigenetics | Methylation status | Blood and buccal cells. Whole genome and locus-specific methylation analysis of stress-related genes53 54 | Birth, after intervention, at 48 to 72 hours, 3 to 4, and 24 months |
| Microbiota | Characteristics: maturation and diversity of the microbiome | DNA analysis from paternal skin and from maternal skin, and stool and vaginal swabs | Birth, 72 hours, 3 to 4, 12 and 24 months |
| Functional brain maturation | EEG sleep and awake patterns, local and global maturation | EEG Galileo NT (EB Neuro, Italy)29 | 4 to 10 days |
| Neurodevelopment | HINE,55
APIB,56 AIMS,57 ASQ,58 IBQ,59 MCHAT60 Bayley scales,61 General motor scales62 |
Term, 3,12 and 24 months |
|
| Mother-infant interaction and stress response | Assessment of emotional and interactive behaviours in the mother-infant dyad | Still Face Paradigm,63
PCERA64 for infant and mother (films) |
4 and 12 months |
| Neuroendocrine response system | Salivary cortisol levels of mother and infant | Salivary cortisol trajectories in relation to a stressor and in normal daytime activity for infant and mother65 | Discharge, 4 and 12 months |
| Parental well-being and mental health | EPDS,66
STAI,67 SPSQ68 for mother and partner |
7 days, term, 3 and 12 months |
The secondary outcomes, tools and time points for data collection. Note: All times for follow-up are corrected ages calculated from the expected date of birth.
AIMS, Alberta infant motor scale; APIB, assessment of preterm infant behaviour; ASQ, ages and stages questionnaire; BSES, breastfeeding self-efficacy scale; CPAP, continuous positive airway pressure; EEG, electroencephalography; EPDS, Edinburgh postnatal depression scale; HINE, Hammersmith infant neurological exam; HRV, heart rate variability; IBQ, infant behaviour questionnaire; IBS, index of breastfeeding status; MCHAT, modified checklist of autism in toddlers; PCERA, parent-child early relational assessment scale; SPSQ, Swedish parenthood stress questionnaire; STAI, Spielberg state-trait anxiety inventory.