Abstract: Objective To analyze the surveillance results of thalassemia and fetal hydrops syndrome in the birth defects surveillance system of Guangdong Province from 2011 to 2021. Method Description analysis was conducted to describe the incidence and diagnosis of thalassemia and fetal hydrops syndrome in Guangdong Province from 2011 to 2021. Results A total of 2 845 496 perinatal infants were monitored from 2011 to 2021. The proportion of mothers <20, 20-24, and 25-29 years old showed an overall downward trend, and the proportion of mothers 30-34 and ≥35 years old showed an overall upward trend, and the annual differences in the proportion of each age group were statistically significant （all P<0.01）. From 2011 to 2021, the overall incidence of thalassemia was 4.02/10 000, showing a downward trend, and the difference between years was statistically significant （P<0.01）; the overall incidence of fetal hydrops syndrome was 5.43/10 000, which showed a decreasing trend, and the difference between years was statistically significant （P<0.01）. The prenatal diagnosis rate of thalassemia increased from 39.75% to 82.39% （P<0.01）, the prenatal diagnosis rate of fetal hydrops syndrome increased from 88.04% to 100.00% （P<0.05）, and the average gestational weeks of prenatal diagnosed showed a decreasing trend. The diagnosis rate of thalassemia and fetal hydrops syndrome by chromosomal or genetic testing or combined with other methods increased from 30.78% in 2011 to 76.19% in 2021 （P<0.01）. Conclusion The overall incidences of thalassemia and fetal hydrops syndrome in Guangdong Province are decreasing, with an increase in prenatal diagnosis rates and a decrease in average gestational age.

Key words: Thalassemia, Fetal hydrops syndrome, Birth defect, Surveillance