Abstract: Objective To explore the clinical value of repeated noninvasive prenatal test(NIPT) for cases with first NIPT results being at average risk. Methods Totally 166 cases who had undergone NIPT tests twice in our hospital from October 2015 to August 2018 were included in our study to analyze the necessity of repeated detection. The inclusion criteria included that the first NIPT yield a result(Z-score) ranged from 1.96 to 4, and second NIPT succeed to provide a test result, meanwhile they had the results of prenatal diagnosis and their pregnancy outcome were followed up by telephone. Results In the first test, 7 of 166 cases were at high risk whose Z value were between 3-4 while second tests all yielded low risk(Z <3); Four of 166 cases were at low risk in the first test(1.96<Z <3), and then they showed high risk after second detection, one case showed high risk for T21(Z=3.37), two cases showed high risk for T18(Z=3.26; Z=4.47) and 1 case with sex chromosomal abnormality(XXY). During the follow-up, one case was confirmed T21 by results of karyotype analysis and fluorescence in situ hybridization and terminated the pregnancy. Abnormalities of chromosome 21, 18, 13 were not found in 165 cases of repeated examination by telephone follow-up. Conclusion It is necessary to carry out repeated NIPT for cases with Z value between 1.96 and 4, which can increase the accuracy of NIPT, reduce the false positive and false negative rate, decrease the number of patients undergoing amniocentesis and improve the efficiency of prenatal diagnosis.