1. choroid plexus cyst (CPC) is a pseudocyst filled with cerebrospinal fluid in the choroid plexus, which is defined as a small, scattered cyst ≥2.0 mm in diameter detected by ultrasound examination of the choroid plexus of the lateral ventricles of the developing fetus at a gestational age of 14-24 weeks. 1.1 More than 90% of CPCs disappear after 26 weeks of gestation, with only a few increasing in size. 1.1 More than 90% of CPCs disappear after 26 weeks of gestation, with only a few showing progressive enlargement.1 CPCs are one of the ultrasound markers of fetal chromosomal abnormalities, which is the significance of detecting CPCs. A total of 10 cases of CPC were detected in pregnant women between 14 and 26 weeks of gestation. The age of the pregnant women ranged from 20 to 38 years old, among which 7 cases were primigravida and 3 cases were menstruation, all of them were pregnant women on 28 years old, and the average age was (32.8±2.5) years old. 1.2 Research methods The instrument used was Esaote AU5, with a probe frequency of 3.5MHz, the examinee took a lying position, and the transabdominal multisectional scanning of the fetal cranial brain structure was carried out, and after the choroid plexus was clearly displayed, the choroid plexus was observed carefully for the presence or absence of echoes within the choroid plexus. The size of the choroid plexus is measured and compared bilaterally, and then the fetal biparietal diameter, head circumference, abdominal circumference, femur length and anatomical evaluation of the spine, heart, stomach, kidneys, bladder and so on are examined in accordance with the routine to exclude other abnormalities. 1.3 Diagnostic criteria Turner et al. suggested that the diameter of the echogenic zone was ≥2.5 mm before 22 weeks of gestation, and the diameter was ≥2.0 mm after 22 weeks of gestation as the diagnostic criteria. 2 .Results Among the 10 cases of CPC in this group, 3 cases were bilateral cysts, 7 cases were unilateral cysts, and 1 case had two cysts on one side, with diameters of about 3～15 mm, which manifested as a clear echogenic area in the lateral ventricle, with a thin cystic wall, smooth edges and rounded shapes. The cysts disappeared after 26 weeks of pregnancy, and 9 cases of full-term fetuses were examined after birth, and all of them had normal development. l case was a senior pregnant woman, 34 years old, and the fetal CPC was bilateral cysts, in which the largest diameter was 15 mm, and it was 18 trisomy. 3, Discussion The choroid plexus is located in the lateral ventricle, the third and fourth ventricles, which is the site of cerebrospinal fluid production.The choroid plexus shown on the sonogram is mainly the choroid plexus located in the lateral ventricle. The best time to examine the fetus for CPC is between 16 and 24 weeks of gestation. Around 26 to 28 weeks of gestation, more than 95% of CPCs “disappear” and can no longer be visualized by ultrasound. If the CPC does not disappear after 26 weeks and is bilateral, amniocentesis, amniotic fluid cell culture or umbilical cord blood culture should be performed in conjunction with other clinical data, in order to exclude chromosomal abnormalities such as trisomy 18 and trisomy 21. The incidence of fetal CPC reported by prenatal ultrasonography is about 0.5-2.9, but it is reported that choroid plexus cysts can be detected prenatally in about 30-50 fetuses with trisomy 18. However, it is reported that choroid plexus cysts are detected prenatally in about 30-50 trisomy 18 fetuses and are the most common manifestation in trisomy 18 fetuses before 24 weeks of gestation. Therefore, after CPC is detected by ultrasonography, a detailed and comprehensive ultrasonography should be performed first to carefully find out whether the fetus has any other abnormal manifestations besides CPC, and it is recommended that the pregnant woman should repeat the ultrasonography after 3 to 4 weeks, so that she can observe the changes of CPC and whether other abnormalities have appeared, especially in the case of pregnant women of advanced age and those with bilateral or multiple CPCs. In conclusion, fetal CPC, as one of the ultrasound markers in prenatal ultrasound diagnosis, suggests an increased risk of fetal chromosomal abnormalities. Clinical consideration should be given to whether or not to karyotype a fetus with CPC based on the presence of other ultrasound abnormalities, maternal age, and serologic screening results.