The majority of women in the United States do not meet recommendations for healthful nutrition and weight before and during pregnancy. Women and providers often ask what a healthy diet for a pregnant woman should look like. The message should be "eat better, not more." This can be achieved by basing diet on a variety of nutrient dense, whole foods, including fruits, vegetables, legumes, whole grains, healthy fats with omega-3 fatty acids including nuts and seeds, and fish, in place of poorer quality highly processed foods. Such a diet embodies nutritional density and is less likely to be accompanied by excessive energy intake compared to the standard American diet consisting of increased intakes of processed foods, fatty red meat, and sweetened foods and beverages. Women who report "prudent" or "health conscious" eating patterns before and/or during pregnancy may have fewer pregnancy complications and adverse child health outcomes. Comprehensive nutritional supplementation (multiple micronutrients plus balanced protein energy) among women with inadequate nutrition has been associated with improved birth outcomes, including decreased rates of low birthweight. A diet that severely restricts any macronutrient class should be avoided, specifically the ketogenic diet that lacks carbohydrates, the Paleo Diet due to dairy restriction, and any diet characterized by excess saturated fats. User-friendly tools to facilitate a quick evaluation of dietary patterns with clear guidance on how to address dietary inadequacies and embedded support from trained health care providers are urgently needed. Recent evidence has shown that although excessive gestational weight gain (GWG) predicts adverse perinatal outcomes among women with normal weight, the degree of pre-pregnancy obesity predicts adverse perinatal outcomes to a greater degree than GWG among women with obesity. Low body mass index and insufficient gestational weight gain are also associated with poor perinatal outcomes. Observational data have shown that first trimester gain is the strongest predictor of adverse outcomes. Interventions beginning in early pregnancy or pre-conception are needed to prevent downstream complications for mothers and their children. For neonates, human milk provides personalized nutrition and is associated with short- and long-term health benefits for infants and mothers. Eating a healthy diet is a way for lactating mothers to support optimal health for themselves and their infants.