Abstract: Objective By analyzing the application of ultrasound in the diagnosis of birth defects in Guangdong Province from 2011 to 2018,to explore the relevant factors affecting the sensitivity of ultrasound diagnosis of birth defects.Methods Data collection according to the national birth defects monitoring programme,statistics and analysis applied to explore the composition changing trend of birth defects diagnostic methods.Results From 2011 to 2018,a total of 208.85 million pregnant women were monitored in 57 birth defect monitoring hospitals in Guangdong Province,and 71 099 defective infants were detected.Among them,43 908 cases were diagnosed by ultrasound or ultrasound combined with other diagnostic methods,accounting for 61.76%.There was significant difference in the annual rate of ultrasound as the basis of diagnosis(χ²=159.23,P<0.05).The birth defects with high sensibility of ultrasound diagnosis were congenital heart disease,congenital hydrocephalus,encephalocele,anencephalus,congenital diaphragmatic hernia,spina bifida,abdominal bifida,conjoined twins,edema syndrome,and umbilical cord swelling.The birth defects with lower sensibility of ultrasound diagnosis were:other malformations of external ear(except for small ear and no ear),multiple fingers(toes),hypospadias,and fingers(toes),small ears(including no ear),recto-anal atresia(including stenosis or anus),Down's syndrome,equinovarus,cleft palate and cleft lip.The diagnostic criteria were ultrasound or ultrasound combined with other diagnostic methods in 43 908 cases,prenatal diagnosis in 23 964 cases,and prenatal ultrasound in 13-27 gestational weeks group had the highest sensibility(74.35%).Conclusion Ultrasound diagnosis can find most fetal structural abnormalities,however,the prenatal ultrasound diagnosis rate of single defect is low.The screening and diagnosis of fetal malformations should be made in advance as far as possible,which is helpful to prevent in the late pregnancy with severe malformation and improve the quality of birth.