Study On Ultrasound Standard Sections In The Prenatal Diagnosis Of Fetal Central Nervous System Abnormalities During The First Trimester

Objective:To evaluate the ultrasonographic appearances of fetal central nervous system and the feasibility of screening fetal central nervous system malformation by using the ultrasonography of standardized section in first-trimester, on the basic of concluding the methodology of diagnosis of fetal central nervous system malformations in middle-late pregnancy. Research data and methods:1. Date:In a period from June 2012 to the end of December 2015,a total of 2751 fetus datasets from 2701 pregnancies who attended their first-trimester screening of fetal nuchal translucency to our hospital.The median maternal age was 26.32 years(range 19-42), the median gestation age was 86.32days(range 77-97). The gestational age of menopause for estimating fetal gestational age will produce larger error, We get the estimated gestation by estimation after measure the crown-rump length with ultrasound to the pregnant women with irregual menstruation. We established profiles for each pregnant woman in the workstation before the screening, such as name, age, last menstrual period, contact information and so on.2. The first trimester sonography strictly followed the guidelines which established by the Fetal Medicine Foundation,UK, and was approved by our Institutional Review Board. All examinations were conducted by physicians who had the qualification. Briefly, all the fetus were examined by high resolution ultrasound machined: Medison V20 and Medison XG, using 2.0~3.5MHz curvilinear transducer. In addition, evaluation of the fetal anatomy for gross fetal anomalies is also performed as recommended by The Fetal Medicine Foundation, such as the survival condition of the fetus, the amount and the size, the measurement of NT and the ductus venosus flow waveform. Then checked the anatomische structure of fetal central nervous system by four standardized section(spine macroaxis section, cephalothorax median sagittal section, cross-sectional view of the fetal lateral ventricle, sectional view of fetal cerebellum and posterior cranial fossa).The asssessment of each fetus include their brain, face, chest, heart, liver, stomach, bladder, umbilical artery, upper limbs, lower limbs and so on. In the end inspectors made detailed records of the measured data and evaluation content.3. All patients were grouped according to fetal gestational age which was estimated by CRL: group 1: 11 weeks to11+6weeks; group 2: 12 weeks to 12+6weeks; group 3: 13 weeks to13+6weeks. Get the measurement of NT and the sectional display situation of each case for statistic, and analyze the relationship between these and the gestation age. Count the relevant data of using ultrasound standardized section to screen central nervous system malformation, such as the detection rate,the sensitivity, the specificity, the positive and negative likelihood ratio, the positive and negative predictive value and so on. Analyze the reason of influence of the detection rata was analyzed. Result:1. There were 20 fetal central nervous system malformations in our series The incidence was 0.509%(14/2751), including 8cases with one deformity(3cases of exencephaly, 2cases of holoprosencephaly, 1case of anencephaly, 2cases of scoliosis)and 4cases with no less than two deformities(1case of anencephaly and opened spina bifida, 1case of anencephaly,opened spina bifida and kyphoscoliosis, 1case of exencephaly and opened spina bifida, 1case of exencephaly, opened spina bifida and scoliosis). The detection rate of fetal central nervous system malformations in the first trimester was 85.7%(12/14), and 2cases in the second trimester. The sensitivity, specificity, positively and negative predictive values were 85.7%,100%,100%and 99.9%.2. 7 of 14 cases of fetal central nervous system malformation were associated with other structural abnormalities(7/12,58.3%),5cases(41.7%)with no less than three deformities(3cases with abnormalities in facial,heart,limbs,and soft index, 2cases of Cantrell pentalogy and central nervous system malformation) and 2 cases( 16.7%) with two deformities( 1 case with left-diaphragmatic and heart right,1case with omphalocele and strephenopodia).In addition, in this group,5 cases with NT>3mm, 2cases with malformations in facial, heart and limbs,2cases of Cantrell pentalogy and central nervous system malformation and 1case are associated with other structural malformations. This group of patients did not indicate a correlation between central nervous system malformation and NT, result of the sample size and most of our positive cases which were associated with other etiological obviously witch can lead to thickening of the NT.3. The display rates of spine macroaxis section, cephalothorax median sagittal section, cross-sectional view of the fetal lateral ventricle, sectional view of fetal cerebellum and posterior cranial fossa were 98.98%,98.15%,99.45% and 98.76%, which were relatively higher. Compare the display rates between different groups(chart2-5), had no statistical significance, there is no correlation between the display rate of fetal central nervous system and fetal gestational age.4. 2703 of 2751 cases of follow-up normal fetus shows a positive correlation between NT and fetal gestational age, result of the correlation analysis between the NT of follow-up normal fetus and fetal gestational age(r=0.154). Conclusion:1. Diagnosis of fetal central nervous system malformation can be done efficient by using ultrasonography of standardized section in first trimester, the display rate is 85.7%.2. The display rate of fetal central nervous system structure is relatively high and not be affected by fetal gestational age.3. The amount of positive cases and the variety of central nervous system malformation are relatively few, and all these positive cases are serious central nervous system malformation. Further study is needed to diagnose other fetal central nervous system malformation.