Diagnostic accuracy of ultrasound screening for fetal structural abnormalities during the first and second trimester of pregnancy in low-risk and unselected populations.

BACKGROUND: Prenatal ultrasound is widely used to screen for structural anomalies before birth. While this is traditionally done in the second trimester, there is an increasing use of first-trimester ultrasound for early detection of lethal and certain severe structural anomalies. OBJECTIVES: To evaluate the diagnostic accuracy of ultrasound in detecting fetal structural anomalies before 14 and 24 weeks' gestation in low-risk and unselected pregnant women and to compare the current two main prenatal screening approaches: a single second-trimester scan (single-stage screening) and a first- and second-trimester scan combined (two-stage screening) in terms of anomaly detection before 24 weeks' gestation. SEARCH METHODS: We searched MEDLINE, EMBASE, Science Citation Index Expanded (Web of Science), Social Sciences Citation Index (Web of Science), Arts & Humanities Citation Index and Emerging Sources Citation Index (Web of Science) from 1 January 1997 to 22 July 2022. We limited our search to studies published after 1997 and excluded animal studies, reviews and case reports. No further restrictions were applied. We also screened reference lists and citing articles of each of the included studies. SELECTION CRITERIA: Studies were eligible if they included low-risk or unselected pregnant women undergoing a first- and/or second-trimester fetal anomaly scan, conducted at 11 to 14 or 18 to 24 weeks' gestation, respectively. The reference standard was detection of anomalies at birth or postmortem. DATA COLLECTION AND ANALYSIS: Two review authors independently undertook study selection, quality assessment (QUADAS-2), data extraction and evaluation of the certainty of evidence (GRADE approach). We used univariate random-effects logistic regression models for the meta-analysis of sensitivity and specificity. MAIN RESULTS: Eighty-seven studies covering 7,057,859 fetuses (including 25,202 with structural anomalies) were included. No study was deemed low risk across all QUADAS-2 domains. Main methodological concerns included risk of bias in the reference standard domain and risk of partial verification. Applicability concerns were common in studies evaluating first-trimester scans and two-stage screening in terms of patient selection due to frequent recruitment from single tertiary centres without exclusion of referrals. We reported ultrasound accuracy for fetal structural anomalies overall, by severity, affected organ system and for 46 specific anomalies. Detection rates varied widely across categories, with the highest estimates of sensitivity for thoracic and abdominal wall anomalies and the lowest for gastrointestinal anomalies across all tests. The summary sensitivity of a first-trimester scan was 37.5% for detection of structural anomalies overall (95% confidence interval (CI) 31.1 to 44.3; low-certainty evidence) and 91.3% for lethal anomalies (95% CI 83.9 to 95.5; moderate-certainty evidence), with an overall specificity of 99.9% (95% CI 99.9 to 100; low-certainty evidence). Two-stage screening had a combined sensitivity of 83.8% (95% CI 74.7 to 90.1; low-certainty evidence), while single-stage screening had a sensitivity of 50.5% (95% CI 38.5 to 62.4; very low-certainty evidence). The specificity of two-stage screening was 99.9% (95% CI 99.7 to 100; low-certainty evidence) and for single-stage screening, it was 99.8% (95% CI 99.2 to 100; moderate-certainty evidence). Indirect comparisons suggested superiority of two-stage screening across all analyses regarding sensitivity, with no significant difference in specificity. However, the certainty of the evidence is very low due to the absence of direct comparisons. AUTHORS' CONCLUSIONS: A first-trimester scan has the potential to detect lethal and certain severe anomalies with high accuracy before 14 weeks' gestation, despite its limited overall sensitivity. Conversely, two-stage screening shows high accuracy in detecting most fetal structural anomalies before 24 weeks' gestation with high sensitivity and specificity. In a hypothetical cohort of 100,000 fetuses, the first-trimester scan is expected to correctly identify 113 out of 124 fetuses with lethal anomalies (91.3%) and 665 out of 1776 fetuses with any anomaly (37.5%). However, 79 false-positive diagnoses are anticipated among 98,224 fetuses (0.08%). Two-stage screening is expected to correctly identify 1448 out of 1776 cases of structural anomalies overall (83.8%), with 118 false positives (0.1%). In contrast, single-stage screening is expected to correctly identify 896 out of 1776 cases before 24 weeks' gestation (50.5%), with 205 false-positive diagnoses (0.2%). This represents a difference of 592 fewer correct identifications and 88 more false positives compared to two-stage screening. However, it is crucial to acknowledge the uncertainty surrounding the additional benefits of two-stage versus single-stage screening, as there are no studies directly comparing them. Moreover, the evidence supporting the accuracy of first-trimester ultrasound and two-stage screening approaches primarily originates from studies conducted in single tertiary care facilities, which restricts the generalisability of the results of this meta-analysis to the broader population.

Early Detection of Isolated Severe Congenital Heart Defects Is Associated with a Lower Threshold to Terminate the Pregnancy.

INTRODUCTION: Early detection of isolated severe congenital heart defects (CHDs) allows extra time for chromosomal analysis and informed decision making, resulting in improved perinatal management and patient satisfaction. Therefore, the aim of this study was to assess the value of an additional first-trimester screening scan compared to only a second-trimester scan in fetuses diagnosed with isolated severe CHDs. Prenatal detection rate, time of prenatal diagnosis, and pregnancy outcome were evaluated in the Netherlands after implementation of a national screening program. MATERIALS AND METHODS: We performed a retrospective geographical cohort study and included 264 pre- and postnatally diagnosed isolated severe CHD cases between January 1, 2007, and December 31, 2015, in the Amsterdam region. Severe CHD was defined as potentially life threatening if intervention within the first year of life was required. Two groups were defined: those with a first- and second-trimester anomaly scan (group 1) and those with a second-trimester anomaly scan only (group 2). A first-trimester scan was defined as a scan between 11 + 0 and 13 + 6 weeks of gestation. RESULTS: Overall, the prenatal detection rate for isolated severe CHDs was 65%; 63% were detected before 24 weeks of gestation (97% of all prenatally detected CHDs). Prenatal detection rate was 70.2% in the group with a first- and second-trimester scan (group 1) and 58% in the group with a second-trimester scan only (group 2) (p < 0.05). Median gestational age at detection was 19 + 6 (interquartile range [IQR] 15 + 4 - 20 + 5) in group 1 versus 20 + 3 (IQR: 20 + 0 - 21 + 1) in group 2 (p < 0.001). In group 1, 22% were diagnosed before 18 weeks of gestation. Termination of pregnancy rate in group 1 and group 2 were 48% and 27%, respectively (p < 0.01). Median gestational age at termination did not differ between the two groups. CONCLUSION: Prenatal detection rate of isolated severe CHDs and termination of pregnancy rate was higher in the group with both a first- and second-trimester scan. We found no differences between timing of terminations. The additional time after diagnosis allows for additional genetic testing and optimal counseling of expectant parents regarding prognosis and perinatal management, so that well-informed decisions can be made.

Increased nuchal translucency before 11 weeks of gestation: Reason for referral?

OBJECTIVES: In this era of non-invasive-prenatal testing (NIPT), when dating scans are usually performed around 10 weeks of gestation, an increased NT before the official established timeframe (CRL between 45 and 84 mm) may be encountered. Information on management of these pregnancies is limited. Therefore, we evaluated the relationship between an early increased NT and adverse pregnancy outcome. Secondary, we evaluated the rate of chromosomal anomalies that might have been missed in first trimester should solely NIPT be performed as first-tier test, and the rate of adverse pregnancy outcome if NT normalizes before 14 weeks. METHODS: We performed a retrospective cohort study that included all pregnancies between January 1, 2007 and June 1, 2020 in Amsterdam UMC locations AMC and VUmc. We included fetuses with a crown-rump length (CRL) < 45 mm (∼11 weeks) and a nuchal translucency (NT) measurement ≥2.5 mm. Fetuses referred with an early increased NT and a major fetal anomaly at the dating scan were excluded, as were cases of parents with a family history of monogenetic disease(s) or recognized carriers of a balanced translocation. RESULTS: We included 120 fetuses of which 66.7% (80/120) had an adverse pregnancy outcome. Congenital anomalies were present in 56.7% (68/120), 45.8% (55/120) had a chromosomal anomaly. The prevalence of congenital anomalies was 30.3% in fetuses with NT 2.5-3.4 mm compared to 66.7% with NT ≥ 3.5 mm (p < 0.001). 16.7% (20/120) had a chromosomal anomaly that might have been missed by conventional NIPT in first trimester. We found an adverse pregnancy outcome of 24% in the group with a normalized NT compared to 78.1% in the group with a persistently increased NT (p < 0.001). CONCLUSION: An early increased NT should make the sonographer alert. In this selected cohort, an early increased NT was associated with a high probability of having an adverse pregnancy outcome. Regardless of CRL, we deem that an early increased NT ≥ 3.5 mm warrants referral to a Fetal Medicine Unit for an extensive work-up. NT normalization seems favorable, but a prospective study should define the appropriate work-up for NT in the lower range (2.5-3.4 mm).

The prevalence of genetic diagnoses in fetuses with severe congenital heart defects.

PURPOSE: Congenital heart defects (CHD) are associated with genetic syndromes. Rapid aneuploidy testing and chromosome microarray analysis (CMA) are standard care in fetal CHD. Many genetic syndromes remain undetected with these tests. This cohort study aims to estimate the frequency of causal genetic variants, in particular structural chromosome abnormalities and sequence variants, in fetuses with severe CHD at mid-gestation, to aid prenatal counselling. METHODS: Fetuses with severe CHD were extracted from the PRECOR registry (2012-2016). We evaluated pre- and postnatal genetic testing results retrospectively to estimate the frequency of genetic diagnoses in general, as well as for specific CHDs. RESULTS: 919 fetuses with severe CHD were identified. After exclusion of 211 cases with aneuploidy, a genetic diagnosis was found in 15.7% (111/708). These comprised copy number variants in 9.9% (70/708). In 4.5% (41/708) sequence variants were found that would have remained undetected with CMA. Interrupted aortic arch, pulmonary atresia with ventricular septal defect and atrioventricular septal defect were most commonly associated with a genetic diagnosis. CONCLUSION: In case of normal CMA results, parents should be offered exome sequencing sequentially, if time allows for it, especially if the CHD is accompanied by other structural malformations due to the large variety in genetic syndromes.

Prenatal sonographic features can accurately determine parental origin in triploid pregnancies.

OBJECTIVE: To describe the prenatal sonographic features and maternal biochemical markers in triploid pregnancies and to assess whether prenatal phenotype can determine genetic origin. METHODS: We performed a retrospective multicenter cohort study that included all triploid pregnancies diagnosed between 2000 and 2018 in two Fetal Medicine Units in Amsterdam. Fetal growth, presence of structural anomalies, extra-fetal anomalies, and maternal biochemical markers were retrieved. Asymmetrical intrauterine growth restriction was diagnosed when the head-to-abdominal circumference (HC/AC) ratio was >95th centile. Parental origin was analyzed via molecular genotyping in 46 cases (38.3%). RESULTS: One hundred and twenty triploid pregnancies were identified, of which 86 cases (71.6%) were detected before 18 weeks of gestation. Triploidy of maternal origin was found in 32 cases (69.6%) and was associated with asymmetrical growth restriction, a thin placenta, and low pregnancy-associated plasma protein A and free beta-human chorionic gonadotrophin (ß-hCG) levels. Triploidy of paternal origin was found in 14 cases (30.4%) and was associated with an increased nuchal translucency, placental molar changes, and a high free ß-hCG. Prospective prediction of the parental origin of the triploidy was made in 30 of the 46 cases based on phenotypical ultrasound presentation, and it was correct in all cases. CONCLUSION: Asymmetrical growth restriction with severe HC/AC discrepancy is pathognomonic of maternal triploidy. Placental molar changes indicate a paternal triploidy. Moreover, triploidy can present with an abnormal first trimester combined test, with serum levels on the extreme end. When available results of maternal serum markers can support the diagnosis of parental origin of the triploidy, an accurate assessment of the parental origin based on prenatal sonographic features is possible, making DNA analysis redundant.