Summary: In people at increased risk of gestational diabetes planning pregnancy, a preconception lifestyle programme of time-restricted eating and exercise did not significantly reduce macrosomia (21% vs 28%; p=0.367) or other neonatal body-composition outcomes compared with standard care, though it was safe.
PICO Summary
| Element | Detail |
|---|---|
| Population | 167 people at increased risk of gestational diabetes planning pregnancy (BEFORE THE BEGINNING; 106 live births in this analysis). |
| Intervention | Preconception and pregnancy lifestyle programme: time-restricted eating (≤10 h/day, ≥5 days/week) plus exercise (≥100 weekly PAI points). |
| Comparison | Standard care without structured lifestyle intervention. |
| Outcome | Birth weight >4 kg in 21% (intervention) vs 28% (control); p=0.367. Mean birth-weight difference -159 g (95% CI -376 to 57; p=0.148). No significant differences in other neonatal or early postnatal body-composition outcomes. |
Preconception lifestyle and newborn outcomes
RCT secondary analysis · GDM risk · 106 births
A preconception programme of time-restricted eating and exercise did not significantly lower macrosomia (21% vs 28%) or other neonatal body-composition outcomes versus standard care. It was safe but is not a reliable way to change birth weight.
Expert Commentary
The preconception window is theoretically the smartest place to intervene, acting before the metabolic demands of pregnancy begin, so I came to this hoping the earlier timing would succeed where antenatal trials have so often failed. It did not, and I think the honest reading is that this null result sits squarely within a disappointing literature. LIMIT, UPBEAT, and DALI all struggled to shift macrosomia or large-for-gestational-age rates through maternal behaviour, and this study, despite starting earlier and using sensible time-restricted-eating and activity targets, reinforces that fetal growth is multifactorial and stubbornly resistant to maternal lifestyle alone. I note the caveats fairly: a secondary analysis, only 106 births, possibly underpowered with a low baseline macrosomia rate, so absence of effect is not proof of no effect. Can I use this with my patients? Yes, but with reframed expectations: I will still encourage healthy eating and activity before pregnancy because it benefits maternal weight, fitness, and health, while being honest that it is not a reliable way to change the baby’s birth weight or body composition. Standard preconception care continues regardless.
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