【Objective】 To explore the correlation between fetal pyelectasis and aneuploidy. 【Methods】 A retrospective study of the karyotypes and delivery outcomes of selected 122 cases with fetal pyelectasis. Invasive prenatal procedures (amniocentesis or cordocentesis) were performed on all 122 patients with ultrasound guidance. 【Results】 Among the 122 fetal karyotypes

87.7% (107/122) were normal karyotype

4.9% (6/122) chromosomal abnormality and 7.4% (9/122) chromosomal polymorphism. All the cases were divided into four groups

Group Ⅰ(67 cases) with isolated pyelectasis

Group Ⅱ (34 cases) in association with one soft marker

Group Ⅲ(7 cases) complicated with two or more soft markers and Group Ⅳ (14 cases) accompanied with fetal structural malformation. From Group Ⅰ to Ⅳ

there were 94% (63 cases)

82.4% (28 cases)

100% (7 cases)

and 64.3% (9 cases) with normal karyotypes

respectively; 4.5% (3 cases)

17.6% (6 cases)

none case

and none case with chromosomal polymorphism; 1.5% (1 case)

none case

none case

and 35.7% (5 cases

including 3 Down syndrome

2 other abnormal karyotypes) with abnormal karyotypes. The 107 successfully followed-up newborns

including 87 boys and 20 girls

made the sexy ratio 4.35:1 (boy: girl). Eleven cases terminated pregnancy. In the 96 alive cases

4 newborns were delivered prematurely

92 were termly

35 eutocia

and 61 cesarean; the average born gestational weeks was 39.1 weeks. Surgeries were carried out on 10 newborns because of hydronephrosis without relieving or exacerbation. 【Conclusion】 Isolated pyelectasis should not be a direct indication of invasive prenatal procedures. However

when fetal pyelectasis is accompanied with other soft markers or fetal structural malformation

invasive prenatal procedures for aneuploidy is advocated. The urinary system function should be followed up closely after birth

and the majority of the pyelectasis fetuses have satisfying prognosis.