Association Between Maternal Protein Intake and the Risk of Adverse Pregnancy Outcomes

Background/Objectives: This study examined the association between low protein intake and pregnancy outcomes to test whether low protein intake was associated with higher rates of small for gestational age (SGA), gestational diabetes mellitus (GDM), and hypertensive disorders of pregnancy (HDP), and lower rates of large for gestational age (LGA). Methods: A secondary analysis was performed using the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (NuMoM2b). Participants missing diet data or pregnancy outcomes and whose pregnancy ended <20 weeks were excluded. Protein intake was calculated in grams per kilogram of bodyweight per day and stratified into quartiles. Multi-variable analyses were done to assess the association between protein intake quartiles and rates of HDP, GDM, SGA, and LGA, adjusting for relevant covariates. Results: Participants (n = 7067) were categorized into quartiles by daily protein intake: Q1 (<0.6 g/kg), Q2 (0.6–<0.8 g/kg), Q3 (0.8–<1.1 g/kg), and Q4 (≥1.1 g/kg). Lower protein intake was common among Black women (p = 0.001), women with less than a high school education (p < 0.001), unemployment (p = 0.004), lower income (p = 0.003), or government insurance (p = 0.04). After adjusting for age, insurance, education, income, chronic hypertension, and dietary kcal, protein intake resulted in significantly lower odds of developing SGA < 10th percentile for women in Q3 (aOR 0.78, 95% CI 0.61–0.99 for Q3). Protein in-take was not significantly associated with HDP, GDM or LGA. Conclusions: Moderate to high protein intake in the first trimester was associated with reduced SGA risk; however, these findings are exploratory and require confirmation in future studies.