Overview of primary (PO) and secondary (SO) outcomes and methods for the randomized controlled trial (RCT)
| Outcome | Variable | Measure | Instrument | Sample size* (incl. dropout)† |
| Preconception diet (PO)‡ | Overall diet Diet quality | Food and nutrient intake Diet score | 2×24 hour recall (myfood24) Food propensity questionnaire | 211 (264)§ |
| Preconception Health-related quality of life (SO) | Health-related Quality of life | Self-reported quality of life | Satisfaction with life scale RAND-12 Health Status Inventory | – |
| Pregnancy health (SO) | Gestational weight gain (GWG) | GWG (absolute measure and relative to guidelines) | Data retrieved from MBRN as recorded in pregnancy records and birth certificate | 1100 (1375)¶ |
| Hypertensive disorders | Preeclampsia yes/no | – | ||
| Gestational diabetes | Gestational diabetes yes/no | 2517 (3147)** | ||
| Neonatal health (SO) | Growth measures at birth | Birth weight, length and head circumference | Data retrieved from MBRN. | – |
| LGA/SGA | 1044 (1305)** | |||
| Gestational age-adjusted weight/length | Birth weight≥4000 g | – | ||
| Newborn adiposity Preterm delivery | Ponderal index (kg/cm‡)<37 weeks of gestation | 461 (577)** |
*Numbers needed in each group. Calculated with a statistical power of 80% and type 1 error of 5%.
†Accounted for a 25% dropout rate in line with other interventions.30
‡Measured at baseline, post intervention and follow-up.
§Healthy Eating Index from The Norwegian Mother, Father and Child cohort (MoBa) (mean score 49.8±7.3 (SD)) used as a proxy for the planned PRECDIET score. As even small improvements in diet are relevant to public health, we assume an increase of 2 points to have a public health impact.
¶Estimation based on the 1 kg decrease in GWG with SD from.28
**Based on proportions from Medical Birth Registry of Norway (MBRN), assuming improvement in line with previous group differences in pregnancy.30
LGA, large for gestational age; SGA, small for gestational age.