Objective: Assessing the effects of maternal anxiety on the markers and results of quadruple screening and on maternal anxiety after receiving positive results. Methods: This prospective cohort study evaluated 1,595 pregnant women referred for prenatal visits. Maternal state/trait anxiety levels were measured, then quadruple screening was performed by measuring serum α-fetoprotein (AFP), β-human chorionic gonadotropin, inhibin A, and unconjugated estriol (UE3). After receiving the results, the state/trait anxiety was remeasured. Amniocentesis was performed for screening-positive mothers. Results: High prescreening maternal anxiety was associated with lower rates of elevated AFP (OR, 0.27; 95% CI, 0.1-0.74) and elevated inhibin A (OR, 0.38; 95% CI, 0.15-0.98). High maternal anxiety was associated with higher rates of decreased UE3 (OR, 1.8; 95% CI, 1.06-3.08). There were no significant associations between prescreening maternal anxiety and the final screening or amniocentesis results. Among the screening-positive mothers, those who had high state/trait anxiety before screening had higher anxiety scores after receiving positive results compared to those with low prescreening anxiety levels (52.9 ± 10.8 vs. 43.7 ± 10.3). Conclusion: High prescreening maternal anxiety is associated with lower rates of elevated AFP and inhibin A and higher rates of decreased UE3. However, maternal anxiety does not affect the final screening or amniocentesis result. High maternal state/trait anxiety before screening is associated with significantly higher maternal anxiety after the receipt of positive results.