Summary: In a secondary analysis of the BEFORE THE BEGINNING trial, a preconception lifestyle intervention in people at risk of gestational diabetes did not significantly reduce large birth weight or change neonatal body composition compared with control.
PICO Summary
| Element | Detail |
|---|---|
| Population | 167 people at increased risk of gestational diabetes and planning pregnancy (106 live births analysed); secondary analysis of an RCT, Norway. |
| Intervention | Preconception lifestyle programme (time-restricted eating ≤10 h/day on ≥5 days/week, plus heart-rate-based exercise), started before and continued through pregnancy. |
| Comparison | Control without the structured intervention. |
| Outcome | Birth weight above 4 kg occurred in 21% (intervention) versus 28% (control), a non-significant difference (p=0.367). Mean birth weight did not differ (mean difference -159 g; 95% CI -376 to 57; p=0.148). No significant between-group differences were found for any other neonatal, birth-related, or early body-composition outcome. The authors found no evidence of effect on macrosomia or neonatal body composition. |
Preconception lifestyle and neonatal outcomes
RCT secondary analysis · GDM risk · preconception to birth
A preconception lifestyle program did not significantly lower large birth weight or alter neonatal body composition. This null result argues against promising a smaller or leaner baby.
Expert Commentary
This is an important negative result, and it should be reported as such rather than dressed up as a benefit. The hypothesis was appealing, that optimising diet and activity before conception and through pregnancy might curb fetal overgrowth in people at risk of gestational diabetes, but the trial found no significant effect on the proportion of large babies, on mean birth weight, or on any neonatal body-composition measure. The numerical trend toward fewer large infants is the kind of signal that can tempt over-interpretation, yet at p=0.367 it is well within chance, and intellectual honesty requires letting the null stand. Several factors plausibly explain it: this was a secondary analysis with only about 106 live births, likely underpowered for neonatal endpoints, and the intervention may simply act on maternal metabolism without translating into measurable neonatal change over this timeframe. Can I use this with my patients? Yes, as honest counselling. I would still encourage preconception health for its broader maternal benefits, but I would not promise that time-restricted eating and exercise before pregnancy will produce a smaller or leaner baby, since this trial did not show that, and I would await larger studies powered specifically for neonatal outcomes.
References
Sujan MAJ, Skarstad H, Rosvold G, et al. Neonatal outcomes following a preconception lifestyle intervention in people at risk of gestational diabetes: secondary findings from the BEFORE THE BEGINNING randomized controlled trial. Nutrients. 2025;17(21):3492. doi:10.3390/nu17213492