The Measures for the Administration of Prenatal Diagnostic Techniques issued by China’s Health and Family Planning Commission (former Ministry of Health) in 2003 stipulates that systematic prenatal ultrasound screening for fetal anomalies should be performed from 20 to 24 weeks and secondary screening from 28 to 32 weeks. In particular, at 11-13 weeks +6, the following aspects of screening must be noted: Screening for soft markers related to fetal chromosomal abnormalities (1) Fetal nuchal translucency thickness (NT) NT ≥3 mm indicates an increased likelihood of fetal abnormalities. 10% of NT thickening is combined with chromosomal abnormalities, the most common being trisomy 21. (2) Fetal nasal bone Abnormal fetal nasal bone development (absent or short) is closely related to chromosomal abnormalities. (3) Venous ductus (DV) and fetal structural anomalies In fetal heart malformations or other pathologies involving altered cardiac hemodynamics, there is an increased right heart load, such as pulmonary stenosis – with an A-wave reversal. Screening for fetal structural anomalies Screening for fetal anomalies should be advanced and early screening for soft markers of fetal chromosomal abnormalities may provide an opportunity for earlier termination of pregnancy in pregnant women with lethal fetal anomalies. Fetal nervous system At 11-13+6 weeks, the general structure of the fetal nervous system is fully developed. The cerebellar earth and corpus callosum are fully developed at 19-20 weeks of gestation, and the cerebral sulcus begins to develop from 23-25 weeks of gestation. Binomial diameter/transverse abdominal diameter predicts open spina bifida, intracranial hyaline layer (IT) screening predicts open spina bifida, and cerebellar medullary pool width predicts posterior cranial fossa anomalies and open spina bifida. Fetal heart anomalies (1) A meta-analysis showed that 537 of 205,232 chromosomally normal fetuses in 20 studies had precocious heart disease (CHD), with NT > 95th and 99th percentiles predicting 45% and 20% of major types of precocious heart disease, respectively, with NT > 99th percentile increasing the risk of CHD more than 20-fold, and NT > 95th percentile The incidence of CHD in chromosomally normal fetuses is 1:48, while the incidence of CHD in fetuses with NT>99th percentile is 1:19.(2) Fetal cardiac axis: Cardiac axis abnormalities are associated with CHD in addition to extracardiac abnormalities. When the cardiac axis is abnormal, it indicates an increased risk of cardiac malformations, especially outflow tract abnormalities. Cardiac axis abnormalities can be associated with chromosomal anomalies, diaphragmatic hernia and thoracic occupancy, and leftward cardiac shift can also be associated with ventral fissure and umbilical bulge. Fetal abdominal anomalies The fetal anterior abdominal wall has a variety of anomalies due to abnormal skin development, such as umbilical bulge, ventral fissure, cloacal and bladder ectopia, corpora tibial anomalies, and a combination of other anomalies. The enlarged bladder may be a normal variant or combined with chromosomal abnormalities and structural abnormalities. Fetal skeletal system Limb anomalies can be diagnosed by 15 weeks, including hand entropion, long bone loss, foot entropion, abnormal ossification, and polydactyly/toe. Fetal anomalies joint signs, sequential signs and syndromes including umbilical bulge, bladder exstrophy, anal atresia, spinal defects – joint malformations. OEIS ultrasound features in early pregnancy: NT thickening, large cystic mass in anterior abdominal wall, thoracic hemivertebrae, lateral posterior spine protrusion, lumbosacral spina bifida, single umbilical artery limb – body wall syndrome.