Detection of non-cardiac fetal abnormalities by ultrasound at 11-14 weeks: systematic review and meta-analysis.

OBJECTIVES: To assess diagnostic accuracy of 2D ultrasound at 11-14 weeks gestation as a screening test for individual fetal anomalies and identify screening factors impacting detection.

METHODS: Systematic review and meta-analysis, developed and registered with PROSPERO (CRD42018111781). MEDLINE, EMBASE, Web of Science Core Collection and The Cochrane Library) were searched for studies evaluating the diagnostic accuracy of screening for 16 pre-specified, non-cardiac, congenital anomalies considered to be of interest to the early anomaly scan. We included prospective and retrospective studies from any healthcare setting and low risk, mixed risk and unselected populations. The reference standard was the detection of an anomaly on postnatal or post-mortem examination. Data were extracted to populate 2 x 2 tables and meta-analysis (random-effects model) undertaken to determine the diagnostic accuracy of screening for the pre-specified anomalies (individually and as a composite). Secondary analyses were performed to determine the impact of (1) imaging protocol (2) ultrasound modality (3) publication year and (4) index of sonographer suspicion at time of scan. Post-hoc secondary analysis was conducted to assess performance for studies from 2010. Risk of bias and quality assessment was undertaken for included studies using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2).

RESULTS: From 5684 citations, 202 papers were identified as eligible and reviewed, resulting in the inclusion of 526,322 fetuses (52 studies) of which 2,399 were affected by one or more of the 16 anomalies. Individual anomalies were not equally amenable to detection on first trimester ultrasound ranging from high (>80%) detection rates for severe conditions including acrania (98%), gastroschisis (96%) and exomphalos (95%) and holoprosencephaly (88%); they were lower for open spina bifida (69%), lower urinary tract obstruction (66%) lethal skeletal dysplasias (57%) and limb reduction defects (50%) and below 50% for facial clefts (43%), polydactyly (40%) and congenital diaphragmatic hernia (38). Conditions with low (<30%) detection rates included bilateral renal agenesis (25%), closed spina bifida (21%), isolated cleft lip only (14%) and talipes (11%). Specificity was >99% for all anomalies. Secondary analysis showed improvement of detection with publication year, and that the use of imaging protocols had a statistically significant impact on screening performance (p<0.0001).

CONCLUSIONS: Accurate detection of congenital anomalies using first trimester ultrasound is feasible. In this study we have determined screening characteristics for individual anomalies and have shown that detection rates and false positive rates are dependent on the type of anomaly. The use of a standardised protocol allows diagnostic performance to be maximised, and this particularly enhances screening performance for the detection of spina bifida, facial clefts and limb reduction defects. Highlighting the types of anomalies amenable to diagnosis and determining favourable screening test factors can support the development of first-trimester anomaly screening programs. This article is protected by copyright. All rights reserved.