Study On The Application Of Fetal Nuchal Translucency Thickness At Early Prenatal Screening

Objective1. To investigate the association between fetal nuchal translucency (NT)thickness and the crown-rump length(CRL)(gestational age).2. To establish normative range of nuchal translucency thickness in Chinese fetuses.3. To evaluate the advantage of different cut-offs for chromosomal aberration.4. To investigate the relation between NT and adverse outcome.Methods1. All 1514 cases were Chinese singleton pregnancies in our hospital collected during April 2006 to April 2008,in 11-13 +6 weeks with CRL 45～84mm.Remove chromosomal abnormalities or structural abnormalities, spontaneous abortion, intrauterine fetal death cases 30, total 1484 normal cases included. The newborn infant were followed at least 6 months,confirmed normal by pediatric medical examination. 2. The pregnancy outcome were obtained by reviewing obstetrics,pediatric record in our hospital or followed by telephone.3. NT measurement were in accordance with FMF standard strictly.4. The gestational age was decided by crown-rump length.5. The association between fetal nuchal translucency thickness and crown-rump length(gestational age) were used regression analysis with SPSS statistics 17.0 software,through the regression equation, the theoretical value of nuchal translucency thickness under different crown-rump length,MoM values were calculated. NT thickness≥2.5mm, 95th percentile of NT thickness MoM values, CRL-specific 95th percentile of NT value were cut-offs for assessing their impact on chromosomal abnormalities.χ2-test for ratio comparing. A P-value of≤0.05 was considered statistically significant.Results1. There was linear association between nuchal translucency and crown-rump length.With the crown-rump length increased from 45mm to 84mm, the median of nuchal translucency thickness from 1.03mm to 2.15mm, the 95th percentile from 1.95mm to 3.07mm(r=0.412,P=0.000).2. The incidence of nuchal translucency thickness greater than or equal to 2.5 mm was increased from 0.2% in fetuses at 11.0-11+6 weeks of gestation to 6.7% in fetuses at 13.0-13+6 weeks.3. Nuchal translucency MoM values showed normal distribution, The 95th percentile was 0.9470+1.64X0.223=1.3.4. NT MoM had no correlation to CRL(P = 0.854).5. 1514 cases, 55 cases of NT thickness≥2.5mm, 60 cases of NT thickness≥1.3MoM, 52 cases of greater than or equal to CRL-specific 95th percentile.10 cases of chromosomal abnormalities (5 cases of trisomy 21, two cases of trisomy 18, three cases of 45, X), 5 cases of congenital heart defects, 5 cases of other structural deformities without karyotype, 10 cases of spontaneous abortion,whose reason were unknown. The NT thickness,if CRL-specific 95th percentile of NT was the cut-off,7 cases of chromosomal abnormalities (13.5%, compared to 0.2% in normal NT group,χ2 = 152.875, P = 0.000) , two cases of cardiac malformation (3.8%, compared to 0.2% in normal NT group,χ2 = 47.294, P = 0.000), 2 cases of other structural deformities(3.8%, compared to the NT group 0.2%,χ2 = 47.294, P = 0.000). if NT thickness≥2.5mm was the cut-off,six cases of chromosomal abnormalities (10.9% compared to normal NT group 0.3%,χ2 = 147.294, P = 0.000), 2 cases of cardiac malformation (3.6% , compared to normal NT group 0.2 %,χ2 = 45.394, P = 0.000), 2 cases other structural abnormalities (3.6%, compared to normal NT group 0.2% ,χ2 = 45.394, P = 0.000), 4 cases of spontaneous abortion (11.7%, compared to normal NT group 0.2%,χ2 = 150.815, P = 0.000), 4 cases of cardiac malformation (6.7% , compared to normal NT group 0.2%,χ2 = 102.975, P = 0.000 ), two cases of other structural abnormalities (3.3%, compared to normal NT group 0.2% ,χ2 = 46.295, P = 0.000), 5 cases of spontaneous abortion (8.3%, compared to NT group 0.3%,χ2 = 112.826, P = 0.000)thickened .6. Through evaluation,if CRL-specific 95th percentile of NT was the cut-off, sensitivity 70%, specificity 97.0%, positive predictive value of 13.5 %, the false positive rate 3.0%; if MoM values'95th percentile was the cut-off (this study was 1.3 MoM), sensitivity 70%, specificity 96.5%, positive predictive value 11.7%, false positive rate of 3.5%; if NT thickness≥2.5mm was the cut-off, sensitivity of 60%, specificity 96.7%, positive predictive value 10.9%, false positive rate of 3.3%. Conclusion1. NT increases with CRL (gestational age).2. The false positive rate increases with CRL (gestational age).3. The distribution of NT MoM values is normal,has no relation to CRL.Its use in clinic can eliminate the impact of CRL (gestational age).4. To eliminate the impact of CRL,NT normal reference range is less than the CRL-specific 95th percentile of NT thickness or less than the 95th percentile of NT MoM.5. For the CRL-specific 95th percentile of NT values, the false positive rate is the lowest, the positive predictive is the best; MoM values followed;for NT thickness≥2.5mm , the positive predictive is the lowest.6. NT thickened, the incidence of chromosomal abnormalities increases.In trisomy abnormalies,the most common is trisomy 21.7. NT thickened,the incidence of heart malformations increases.8. Nuchal translucency thickend,further prenatal diagnosis should be offered to exclude chromosomal abnormalities or early second trimester ultrasound scan should be offered to exclude structural abnormalities. Objective1. To explore the effectiveness of the nuchal translucency in the first-trimester combined screening;2. To investigate the effectiveness of the first-trimester combined screening;3. To provide the guide for clinical prenatal screening choosing.Methods1. 1514 cases of Chinese singleton pregnancies in our hospital, which were followed up were collected from April 2006 to April 2008.2. Their pregnancy outcomes were obtained by overviewing records from neonatal division, children-caring, obstetrics and telephone. The neonatal were followed up at least 6 months.3. NT measurement were in accordance with FMF standard strictly.4. Maternal serum markers were mearseared by Autodelfia platform.5. The risk of Down's syndrome were calculated by using multivariate normal distribution and lifecycle software.6. SPSS software17.0 was used for the data analysis.Results 1. Observation of NT, PAPP-A, fβ-HCG for 1482 cases of affected singleton pregnancies showed the median,5th percentile,95th percentile of PAPP-A,NT increased from 11 to 13 weeks gestation, while the fβ-HCG decreased.10 cases of anuploedy, NT≥1.3MoM in 7 cases, fβ-HCG≥2.5 MoM in five,PAPP-A≤0.43 MoM in 7.2. Using a risk cut-off level of 1 in 250, nine of 10 fetal aneuploidies were identified with a 4.8% false-positive rate, including four with trisomy 21, two with trisomy 18, and three with Turner's syndrome.3. Using a risk cut-off level of 1 in 250 for PAPP-A and fβ-HCG, three with trisomy 21( 60%), one with trisomy 18( 50%), and two with Turner's syndrome( 66.7%) were identified.4. Fβ-HCG sensitivity was 50%,odds 11.6;PAPP-A sensitivity 70%,odds 13.4; NT sensitivity 70%, odds 63.9; combined screening sensitivity 90%, odds 144.8.Conclusion1. NT is an effective ultrasound marker for fetal abnormalities screening.The combined screening(NT+PAPP-A+fβ-HCG)will increase the detection rate more than the serum markers,which NT doesn't join in.2. The first trimester combined screening can make the prenatal diagnosis time earlier.And its detection rate higher than the second-trimester.3. First-trimester combined screening is more effective than each marker alone.