This research design used an analytical method with a research design. The data collection process comes from primary and secondary data using questionnaires and antenatal care visit logbooks. The population in this study were 53 pregnant women with the majority of good knowledge as many as 20 people (37.7%) and among the 20 people who had good knowledge there were 13 people (65%) who did not gain weight. Meanwhile, there were 33 mothers with poor knowledge (62.3%) and among the 33 people with poor knowledge, there were 30 people (90.9%) who did not gain weight. Research shows that maternal knowledge about nutrition of pregnant women affects X ² 165.97 ≥ 3,841 significantly related to knowledge of pregnant women about nutrition with weight gain during pregnancy at the Roslena Clinic in Medan in 2019 with X² count ≥ X² table. Thus, it is hoped that the health workers at the Roslena Medan Clinic in 2019 will provide health education or information about the nutrition of pregnant women that the mother needs during pregnancy when the mother comes to conduct a pregnancy check at the Roslena Medan Clinic in 2019.