Rates of childhood obesity have increased over the last few decades. Overweight and obesity during childhood is associated with obesity in adolescence and adulthood, as well as increased risk of immediate and long-term health consequences. Because the risk of child obesity may be programmed before birth, understanding the role of the fetal environment is imperative. Maternal diet quality during pregnancy is a modifiable factor that may influence the development of child obesity; however, few studies have examined this association. We used data from the Pregnancy, Infection, and Nutrition study, a prospective, longitudinal pregnancy cohort, to examine the role of maternal dietary patterns during pregnancy on maternal cardiometabolic markers and child growth from birth to 36 months. Dietary patterns were derived using the Dietary Approaches to Stop Hypertension (DASH) diet and latent class analysis (LCA). Three dietary patterns emerged from LCA characterized by high intakes of: 1) hamburgers, hot dogs, bacon, French fries, fried chicken, white bread, and soft drinks; 2) some vegetables, fruit juice, refined grains, mixed dishes, processed meat, and empty calorie foods; and 3) fruits, vegetables, whole grains, low fat dairy, breakfast bars, and water. DASH scores were categorized into tertiles. Using multivariable linear regression, we found that healthier diet quality (highest DASH tertile and Latent Class 3) was associated with lower insulin, insulin resistance, and triglyceride levels compared to poorer diet quality (lowest DASH tertile and Latent Class 1). At 36 months, there was suggestion of a positive association between higher maternal DASH score and BMI z-score. Using linear mixed models, we found that, on average, children of mothers with a DASH diet score <28, representing poorer diet quality, had a higher weight-for-height z-score from birth to 36 months than children of mothers with a DASH diet score ≥28. We did not find evidence that maternal DASH score influenced the rate of childhood growth from birth to 36 months. Our results support maternal diet quality as a modifiable behavioral factor that may be useful in intervention efforts to improve maternal cardiometabolic health during pregnancy and reduce the burden of childhood obesity.