Research has established that maternal diet influences fetal growth and preterm birth, but most studies only evaluate single nutrients. Relations between dietary patterns and neonatal outcomes are understudied. We evaluated associations of neonatal outcomes with maternal diet patterns derived using 3 a priori diet scores [Alternative Healthy Eating Index-2010 (AHEI-2010), alternate Mediterranean diet score (aMed), and Dietary Approaches to Stop Hypertension (DASH)] as well as principal components analysis (PCA). We studied 1948 women from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Singletons, a racially diverse multisite cohort of pregnant women in the USA (2009-2013). Diet in the past 3 mo was assessed using a self-administered FFQ at 8-13 weeks of gestation. Birthweight was abstracted from medical records and neonatal anthropometry measured postdelivery using standardized protocols. All 3 a priori scores were significantly associated with increased birthweight, and aMed was also associated with reduced odds of low birthweight [quartile 4 versus 1: ORadj=0.42; 95% CI: 0.18, 1.00 (P-trend=0.02)]. Greater aMed and DASH scores were significantly associated with increased length [aMed: quartile 4 versus 1: 0.54 cm; 95% CI: 0.10, 0.99 (P-trend=0.006); DASH: quartile 4 versus 1: 0.62 cm; 95% CI: 0.25, 0.99 (P-trend=0.006)] and upper arm length. Neither diet pattern derived from PCA was significantly associated with birthweight. Among mostly low-risk pregnant women, pre- and early pregnancy healthful diet quality indices, particularly the aMed score, were associated with larger neonatal size across the entire birthweight distribution. In the absence of generally accepted pregnancy-specific diet quality scores, these results provide evidence for an association between maternal diet patterns and neonatal outcomes.