First-trimester screening for fetal structural and chromosomal anomalies by detailed early anomaly scan

Abstract

Objectives To assess the performance of first trimester ultrasound screening for fetal structural and chromosomal anomalies based on a detailed anomaly and nuchal translucency (NT) scan at 11–13+6weeks' gestation. Methods A prospective cohort study was conducted at Nanjing Drum Tower Hospital. Fetuses with a crown-rump length (CRL) between 45 mm and 84 mm scanned during December 2015 to March 2016 were enrolled in this study. After a detailed first-trimester anomaly scan followed the protocol of systematic standardized scan plans, fetuses with congenital abnormalities were screened out. Second trimester ultrasound screening and postnatal examination were performed for further examination of fetal anomalies. Cytogenetic analysis was performed on the fetuses with informed consent. Results (1) A total of 1 154 fetuses were enrolled in this study and among them, 36 (3.1%) cases of fetal abnormalities were diagnosed through prenatal examination (35 cases) and postnatal examination (one case). (2) Twenty-one (58.3%) out of the 36 cases with structural and chromosomal anomalies were screened out by using the first-trimester scan, including eight cases of congenital cardiac defect (two cases of atrioventricular septal defect, one case of tricuspid atresia, one case of tetralogy of tetralogy, one case of right ventricle aneurysms and one cases of hypoplastic left heart syndrome combined with cystic hygroma with one case combined with polydactyly), four cases of central nervous system anomaly (three cases of exencephaly and one case of anencephaly combined with double outlet right ventricle), two cases of cleft palate/lip with one case combined with double outlet right ventricle, two cases of exomphalos, one case of amniotic band syndrome, one case of spinal bifida combined with megacystis, one case of umbilical cyst, one case of polydactyly and one case of cystic hygroma. One case of twin pregnancy chose selective fetocide to the fetus with exencephaly and 16 cases terminated pregnancy. The other four cases were confirmed by second trimester ultrasound screening and postnatal examination. Fourteen (38.9%, 14/36) new cases of structural and chromosomal anomalies were detected by the second-trimester scan, six of which terminated the pregnancies and the rest were confirmed at term. One (2.8%, 1/36) case of polydactyly was detected postnatally. (3) Chromosomal microarray analysis was performed on 28 cases, seven of which were identified as having chromosomal abnormalities including five cases detected in the first trimester and two cases detected in the second trimester. (4) Out of the 20 fetuses with abnormal NT in early trimester, which accounted for 1.7% of all enrolled fetuses, nine were indentified with major structural or chromosomal abnormalies, a quarter of all abnormal fetus. Conclusions Detailed anomaly scan and NT scan in the first-trimester can increase the detection rate of fetal structural and chromosomal anomalies as compared with the traditional NT scan and provide earlier detection of severe fetal abnormalities as compared with second trimester anomaly scan. Key words: Pregnancy trimester, first; Ultrasonography, penatal; Congenital anormalities; Chromosome aberrations