LAUSR

BACKGROUND First trimester ultrasound scans were introduced to China for nearly 20 years. The ability of first-trimester ultrasound screening to detect different malformations was variable. A recent systematic review concluded that the use of a standardized anatomical protocol was the most crucial factor to improve the sensitivity of first-trimester ultrasound screening for anomalies. Standardized sectional scans have long been used for routine anatomy screening during the second trimester. However, during the first trimester, the majority of the previous studies have described the observation of anatomical structures but have not specified clearly the standard sectional views. OBJECTIVE We aimed to determine the performance of routine first trimester scans using a standardized anatomical protocol for detecting structural abnormalities in China. STUDY DESIGN This was a large retrospective study involving 59063 sequential unselected pregnancies. 11-13+6week scans were performed in a single center during a 7-year span. All fetuses were examined following a pre-defined protocol for standardized views. RESULTS From October 2008 to December 2015, first trimester scans were performed in 53349 pregnant women with available outcome. Of these, there were 1578 (3%) pregnancies that presented with at least one fetal structural abnormality. The detection rate for first-trimester screening was 43·1% (95%CI 40·6%-45·5%). Routine first trimester scans detected 95·6% of abdominal wall defects, 66·3% of nervous system defects, 33·8% of limbs and skeleton malformations, 30·8% of facial and 21·2% of urogenital, 18·4% of thoracic and lung abnormalities and 4·1% of gastrointestinal tract abnormalities. 37·7% of cardiac defects was identified during the first trimester and included 57·9% of major cardiac defects and 2·6% of mild cardiac defects. A robust high detection rate for anencephaly, exencephaly, cephalocele, holoprosencephalys, exomphalos, gastroschisis, pentalogy of Cantrell, sirenomelia and Body stalk anomaly was achieved during routine first trimester scans. CONCLUSIONS A standardized anatomical protocol is advised when performing routine first-trimester ultrasound screening. It is recommended that screening for severe structural abnormalities should be extended to the first trimester.