Early pregnancy is commonly accompanied by a wide range of symptoms, yet psychological determinants of pregnancy-related symptom burden remain poorly understood. Evidence from other medical contexts suggests that expectations may contribute to symptom burden. This prospective study examined whether first-trimester symptom expectations predict pregnancy-related symptom burden and disability at the beginning of the second trimester. In the PrExpect study, pregnant women up to the 10th gestational week completed online questionnaires assessing pregnancy-related symptoms, symptom expectations, psychological variables, and pregnancy characteristics, with follow-up at the beginning of the second trimester. Hierarchical regression models identified predictors of symptom burden and disability. Bidirectional temporal associations between symptoms and expectations were examined using a cross-lagged panel model. Exploratory analyses assessed pregnancy-related mindsets. A total of 347 women provided baseline data, and 227 completed follow-ups. Symptom burden was high and increased across the first trimester. Stronger baseline symptom expectations consistently predicted greater symptom burden and disability at follow-up. Cross-lagged analyses indicated bidirectional associations between expectations and symptoms over time. Several negative pregnancy-related mindsets were associated with higher symptom burden. These findings identify symptom expectations as a psychological correlate of early pregnancy-related symptom burden and disability, suggesting that symptom expectations may represent a promising target for future intervention studies to support well-being in early pregnancy.