BackgroundMaternal nutrition during pregnancy is essential to fetal growth and producing a healthy child. This study aims to investigate the relationship between maternal dietary diversity and neonatal weight among pregnant women referred to health centers in Qazvin.MethodsThis was a cross-sectional study of 1076 pregnant women referred to healthcare centers affiliated by Qazvin University of Medical Sciences from April to June 2019. The dietary information of study participants was collected by a food frequency questionnaire. It was used to determine their dietary patterns by applying a factor analysis with a varimax rotation using SPSS software, version 20. Regarding the women's Dietary Diversity Score (DDS), women were categorized into two groups: inadequate (DDS < 4) and adequate (DDS ≥ 4) dietary diversity. The primary outcome was birth weight, and a log-binomial model was run to test the association between DSS and birth outcomes in the study population. The analysis was performed using SPSS Statistics for Windows version 20.0.ResultsStudy findings revealed that mothers with higher dietary diversity scores were those with normal BMI and normal levels of hemoglobin who had 8–10.9 kg maternal weight gain and were headed by an employed husband (P < 0.05). Furthermore, the risk of low birth weight in newborns of mothers with inadequate dietary patterns was 2.6 times higher (ARR = 95% CI 2.6, 1.4, 5.12) compared to the newborns from mothers with adequate diets.ConclusionInsufficient intake of dietary diversity during pregnancy can potentially increase the likelihood of low birth weight in newborns. Thus, we recommend that health system authorities prioritize the planning for healthy nutrition of pregnant mothers in different geographical regions, specifically remote, rural, and deprived areas of the country.