Abstract： Objective To evaluate the association between fetal ventricular septal defects (VSD)and chromosomal abnormalities.Methods The 214 fetuses diagnosed VSD in the First Affiliated Hospital of Sun Yat-sen University from January 2008 to September 2011 were included.The VSD were categorized into 3 types:perimembranous,muscular and mixed (the defect could not be classified because the dimensions were larger than 5 mm) type.The perimembranous defect was subdivided into inlet and outlet subtypes.Complicated with other cardiac abnormalities/extracardiac abnornalities or not,the cases were divided into isolated VSD group,VSD complicating cardiac anomalies group (other cardiac and/or great vessels malformation),VSD complicating extracardiac anomalies group (include organ malformation and sonographic soft markers) and VSD with both cardiac and extracardiac anomalies group.G-banding chromosome analysis was advised for all cases.In cases that no karyotype was obtained,the phenotype of the newborns was examined by the pediatricians.And those appeared normal were defined as normal karyotype.Results (1) There were 134 (62.6％,134/214) perimembranous defects,including 91 (42.5％,91/214) inlet lesions and 43 (20.1％,43/214) outlet lesions.There were 35 (16.4％,35/214) muscular defects and 45 (21.0％,45/214) mixed type lesions.(2) Among the 214 VSD fetuses,46 (21.5％) were isolated VSD,34 (15.9％) were cases with other cardiac anomalies,87 (40.6％) were cases with extracardiac anomalies and 47 (22.0％) were cases with both cardiac and extracardiac anomalies.(3) The chromosomal karyotypes were obtained in 105 cases,and 21 cases were considered as normal according to the phenotype.Of all these 126 cases,46 (36.5％,46/126) had chromosomal abnormalities.(4) Inlet defects had the highest risk of chromosomal abnormalities (28/55,50.9％),while the muscular defects had the lowest risk (2/25,8.0％).The incidence of chromosomal abnormalities in outlet and mixed type was 33.3％ (9/27) and 7/19,respectively.The types of VSD were significantly correlated with chromosomal defects (P ＜ 0.01).(5) The incidence of chromosomal abnormalities in the 4 groups were 3.4％ (1/29),2/14,53.6％ (30/56) and 48.1％ (13/27),respectively.The risk of chromosomal abnormalities in the cases complicating extracardiac or both extracardiac and cardiac anomalies was significantly higher than the isolated VSD group (P ＜ 0.01).Conclusion Fetal VSD had a highest risk of chromosomal abnormalities,especially the inlet type and VSD with extracardiac abnormalities,and then the fetal karyotype should be recommended.