| Objectives(1)To study the relevance between cervical vertebra interval of fetus by using 3D ultrasound and to explore the method of locating fetal centrums and ribs with 3D ultrasound.(2)To discuss the effect of axis positioning method in prenatal ultrasound diagnosis of fetal abnormal number of ribs and to analyze the distribution characteristics and misdiagnosis reasons of abnormal rib number.(3)To discuss the relevance between abnormal rib numbers and chromosomal abnormalities in prenatal ultrasound screening and to provide theoretical basis for the prenatal diagnosis and genetic counseling.Materials and Methods(1)A total of 223 cases of normal single pregnancy in the second trimester that received routine prenatal screening in Shenzhen People's Hospital from June 2016 to December 2016 were enrolled in the study.Routine systematic scanning was carried out to check the fetal structure.Long axis midsagittal plane was taken as the starting plane to acquire the 3D volume of fetal spine and 4DView software was used for imaging analysis.The distances between transverse processes of cervical vertebra were measured in vertical horizontal line.In order to minimize measurement error and bias,all measurements were taken by one person for two times and the mean values were used for analysis.The distance between the first and second cervical vertebra was labeled C1,and then followed by C2,C3,C4,C5 and C6.(2)Ultrasound systematic screening was carried out on 9105 singleton fetuses in the second trimester.The occurrence rate of abnormality in fetal rib numbers and the varieties were analyzed.Among them,151 cases with suspected rib number abnormality were selected and diagnosed by Doctor A and Doctor B using 3D ultrasound,respectively.Doctor A adopted axis positioning method mentioned in part one which was taken as the observation group and Doctor B adopted routine counting method as the control group.All the cases were confirmed by chest X-ray.The accuracy of two rib counting methods were analyzed and reasons of misdiagnosis was discussed.(3)A total of 60 fetuses with abnormality in rib number received chromosome examination and 142 normal fetuses received invasive chromosome examination were enrolled.Group A was isolated abnormality in rib number,was catogroried in Group A,non-isolated abnormality in rib number in Group B and normal fetuses in Group C.All fetuses were followed up and compared with gross specimen after delivery.Results(1)The 3D imaging of 206 cases of spine in the group was enrolled with a show rate of 92.4%.ICC values of C1~C6 were 0.985,0.984,0.971,0.956,0.978,0.923,respectively and the data measuring consistency was well.The difference between C1 and C2~C6 had statistical significance(P=0.012)and the ratios of C1 to C2~C6 were 1.41,1.39,1.37,1.40,1.39,respectively,which had no correlation with gestational ages(p>0.05)and p values were 0.877,0.915,0.838,0.859,0.908,respectively.(2)In this group,abnormality in fetal rib number was detected in 285 cases(3.14%),isolated abnormality in fetal rib number was detected in 108 cases(1.96%)and abnormality in fetal rib number complicating with other abnormalities were detected in 97 cases(1.18%);the occurrence frequency of abnormalities from high to low was cardiovascular system abnormality > nervous system abnormality > urogenital system abnormality > digestive system abnormality > others > skeletal system dysplasia.The diagnostic accuracy of Doctor A was 97.1%,Doctor B 89.5% and the difference of two doctors had statistical significance(P=0.032).(3)Chromosome results of 60 cases with abnormal fetal rib number: chromosome abnormality was detected in 14 cases(23.3%).There were 27 cases in group A with 4 cases of abnormal chromosome(14.8%)and 33 cases in group B with 10 cases of abnormal chromosome(30.3%).There were 142 cases in group C with 2 cases of abnormal chromosome(1.4%).The difference between group A and group B had no statistical significance(P=0.158).The difference between group A and group C had statistical significance(P=0.004).The difference between group B and group C had statistical significance(P=0.000).Among 14 cases with abnormal chromosome,10 cases got minor changes in chromosome(71.4%)with 4 cases of micro-repeat or micro-deletion in 16p11.2 segments(28.6%).Conclusions(1)The display rate of fetal spine 3D imaging is high.The proportional relationship between C1 and C2 ~ C6 can be used to recognize the second cervical vertebra and to locate and count the spine from top to bottom.Fetal rib positioning and count problems can be solved via the connective relationship between ribs and spine.(2)Most abnormalities in fetal rib number are isolated changes.However,they can also be complicated with other abnormalities,with cardiovascular system abnormality as the most common one.Counting ribs by axis positioning method is superior to the conventional rib count method.(3)Most abnormalities in fetal rib number are normal variations,but some of them are related to chromosomal abnormalities.If the rib number abnormalities were accompanied by other defects,the risk of chromosomal abnormalities will be higher.Most abnormalities in fetal rib number are minor changes in chromosome and may be associated with micro-repeat or microdeletion in 16p11.2 segments. |
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