Old Question Revisited: Are High-Protein Diets Safe in Pregnancy?
Level 3 - non-randomized controlled study
Non-randomized prospective cohort study combining two large national birth cohorts
PubMed 33572843 · doi:10.3390/nu13020440
What was done
Individual participant data on singleton pregnancies from the Danish National Birth Cohort (n = 60,141) and the Norwegian Mother, Father and Child Cohort Study (n = 66,302) were harmonized (total n = 126,443). Diet was assessed via dietary records in mid-pregnancy. The study evaluated associations between maternal protein intake levels and birth outcomes (preterm delivery, low birth weight, and fetal or neonatal death) extracted from national birth registries.
What was found
Mean protein intake was 89 g/day (SD 23). Prevalences were: preterm delivery 4.77%, low birth weight 2.93%, fetal death 0.28%, and neonatal death 0.17%. High protein intake (>100 g/day) was not associated with low birth weight, changes in mean birth weight, or fetal/neonatal death. High compared to moderate intake (80-90 g/day) was associated with a modest increase in preterm delivery (OR 1.10, 95% CI 1.01 to 1.19), driven by late preterm deliveries (weeks 34 to <37), without higher risk at more extreme intakes. Very low protein intake (<60 g/day) was associated with higher risk of low birth weight (OR 1.59, 95% CI 1.25 to 2.03) compared to moderate intake.
Why it matters
Unlike the historical Harlem Trial intervention, this large observational analysis found no link between high maternal protein intake and fetal growth restriction or perinatal mortality, though a weak association with late preterm birth was observed.
Limits
The study is observational and prone to residual confounding. Dietary intake was self-reported at a single mid-pregnancy timepoint. The sample was restricted to Nordic cohorts with generally adequate baseline nutrition, potentially limiting generalizability to populations with different baseline nutritional risks.
Cited by
- supports Across studies in pregnant women, low-protein diets lead to smaller babies.