Prenatal screening for serious congenital heart defects using nuchal translucency: a meta-analysis

Prenatal Diagnosis of Euploid Increased Nuchal Translucency on Fetal Ultrasound (II): RASopathy Disorders - Prenatal Ultrasound Findings and Genotype-phenotype Correlations

Prenatal diagnosis of euploid increased nuchal translucency (NT) remains a challenge to obstetricians and genetic counselors, although increased euploid NT at prenatal diagnosis can be associated with a favorable outcome. Prenatal diagnosis of euploid increased NT should include a differential diagnosis of pathogenetic copy number variants and RASopathy disorders (RDs) including Noonan syndrome. Therefore, chromosomal microarray analysis, whole-exome sequencing, RASopathy-disorder testing, and protein-tyrosine phosphatase nonreceptor type 11 gene testing may be necessary under such a circumstance. In this report, a comprehensive review of RDs with its prenatal ultrasound findings and genotype-phenotype correlations is presented.

Elevated hsa-miR-99a levels in maternal plasma may indicate congenital heart defects

The current standard for prenatal screening is mostly based on biochemical marker tests and the use of ultrasonography. There is no secure stand-alone screening marker for congenital heart defects (CHDs). MicroRNAs (miRNAs) that are associated with cardiogenesis enter the maternal peripheral bloodstream during pregnancy and allow non-invasive prenatal testing (NIPT). The present study investigated the plasma expression profile of fetal hsa-miR-99a in maternal blood. Peripheral blood samples were collected from 39 pregnant patients, comprising 22 with CHD-positive fetuses and 17 with CHD-free controls. miRNAs were isolated from the maternal serum and reverse transcription-quantitative polymerase chain reaction was carried out to determine the expression of hsa-miR-99a. While the miRNA concentrations were almost identical among the affected and control groups (5.54 vs. 6.40 ng/µl), significantly upregulated hsa-miR-99a levels were identified in the affected group (1.78×10^-2±3.53×10^-2 vs. 1.09×10^-3±3.55×10^-3 ng/µl, P=0.038). In conclusion, according to the present study, hsa-miR-99a is involved in cardiac malformation and may serve as a biomarker during fetal development, and therefore presents as a candidate for monitoring cardiomyogenesis and potential use as a NIPT-biomarker for fetal CHD.

Prenatal screening methods for aneuploidies

Aneuploidies are a major cause of perinatal morbidity and mortality. Therefore, it is the most common indication for invasive prenatal diagnosis. Initially, screening for aneuploidies started with maternal age risk estimation. Later on, serum testing for biochemical markers and ultrasound markers were added. Women detected to be at high-risk for aneuploidies were offered invasive testing. New research is now focusing on non-invasive prenatal testing using cell-free fetal DNA in maternal circulation. The advantage of this technique is the ability to reduce the risk of miscarriage associated with invasive diagnostic procedures. However, this new technique has its own set of technical limitations and ethical issues at present and careful consideration is required before broad implementation.

Second trimester serum predictors of congenital heart defects in pregnancies without chromosomal or neural tube defects

OBJECTIVE

To compare euploid pregnancies with congenital heart defects (CHDs) to similar pregnancies without CHDs on typically collected second trimester biomarker measurements.

METHOD

Second trimester serum levels of alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), and unconjugated estriol were compared for 306 CHD cases and 1224 no-CHD controls drawn from a sample of singleton pregnancies without chromosomal or neural tube defects (NTDs). Logistic regression models were built comparing biomarkers for cases and controls.

RESULTS

Regardless of the severity of defect, CHD cases were more likely to have unusually high AFP and/or hCG levels and/or unusually low hCG and/or uE3 levels [odds ratio (OR) 1.8-2.4, 95% confidence intervals (CIs) 1.2-4.0]. Cases with critical CHDs were more than twice as likely to have an AFP multiple of the median (MoM) ≥ the 95th percentile and/or an hCG and/uE3 MoM ≤ the 5th percentile (OR 2.1-3.9, 95% CIs 1.1-7.8).

CONCLUSION

Abnormal levels of specific second trimester maternal serum biomarkers indicated an increased risk for CHDs among this sample of low risk pregnancies. Our data suggest that future efforts aimed at improving CHD detection in low risk pregnancies may benefit from considering serum biomarkers.

Potential role of maternal serum microRNAs as a biomarker for fetal congenital heart defects

Congenital heart defects (CHD) are the most common form of major birth defect, affecting almost 1% of live births. These defects place a significant economic burden on the National Health Service and on the psychological wellbeing of affected families. The early screening and identification of neonates with CHD could reduce morbidity and mortality by allowing proactive medical treatment and parental counseling about options during pregnancy, including termination. Fetal echocardiography is the principal screening tool for the identification of CHD, but its accuracy mainly depends on the skill and experience of the operator. Various biomarkers of screening for fetal CHD are currently available, such as nuchal translucency (NT), β-hCG and PAPP-A; however, these are non-specific indexes with high incidences of false positive results. Certain specific microRNAs (miRNAs) of cardiogenesis have been identified, which correlate positively with placental miRNA expression. These miRNAs of placental origin can be detected in maternal peripheral blood. Therefore, we postulate that these maternal serum miRNAs may be a potential biomarker for fetal CHD.

The prenatal diagnosis of genetic diseases

BACKGROUND

Prenatal diagnosis is a subfield of clinical genetics and gynecology that exemplifies the effective integration of theoretical and clinical medicine. Milestones in its history include the development of cytogenetic, molecular genetic, and molecular cytogenetic methods as well as advances in ultrasonography. The latter technique not only improves the safety of invasive procedures, but also enables earlier and more reliable diagnosis of congenital malformations.

METHODS

This article provides an overview of the subject in the light of selectively reviewed literature, guidelines, and recommendations.

RESULTS AND CONCLUSION

Invasive prenatal diagnosis is most commonly performed to assess the embryonal/fetal chromosome set. An increasing number of monogenic diseases can be diagnosed prenatally by either genetic or biochemical testing, depending on the particular disease being sought. Polygenic and multifactorial diseases cannot be reliably diagnosed by genetic testing at present, although a number of malformations can be ascertained prenatally by ultrasonography. We discuss the applications and limitations of invasive and noninvasive techniques for prenatal diagnosis.

Increased nuchal translucency in euploid fetuses--what should we be telling the parents?

Nuchal translucency (NT) measurement between 11 and 14 weeks' gestation is an undisputed marker for aneuploidies. When conventional karyotyping is normal, enlarged NT is a strong marker for adverse pregnancy outcome, associated with miscarriage, intrauterine death, congenital heart defects, and numerous other structural defects and genetic syndromes. The risk of adverse outcome is proportional to the degree of NT enlargement. Although the majority of structural anomalies are amenable to ultrasound detection, unspecified genetic syndromes involving developmental delay may only emerge after birth. Concern over these prenatally undetectable conditions is a heavy burden for parents. However, following detection of enlarged NT the majority of babies with normal detailed ultrasound examination and echocardiography will have an uneventful outcome with no increased risk for developmental delay when compared to the general population. Counseling should emphasize this to help parents restore hope in normal pregnancy outcome and infant development.

Intra- and interobserver repeatability of fetal cardiac examination using four-dimensional spatiotemporal image correlation in each trimester of pregnancy

OBJECTIVE

To assess the intra- and interobserver repeatability of the evaluation of fetal cardiac structures and measurements using spatiotemporal image correlation (STIC) technology in each trimester of pregnancy.

METHODS

Four-dimensional (4D)-STIC volumes from 150 low-risk pregnancies were acquired at first-, second- or third-trimester scan for later analysis by two different reviewers. A total of 19 items, including the evaluation of 14 structures as well as five measurements of the fetal heart, were evaluated. The reliability of qualitative variables was evaluated using Cohen's kappa and absolute agreement analysis while that of quantitative parameters was assessed using the intraclass correlation coefficient (ICC).

RESULTS

Forty-five, 47 and 47 STIC volumes were included in the final analysis from the first, second and third trimesters, respectively. For the evaluation of cardiac structures, good or excellent intra- and interobserver agreement (kappa > 0.6) was obtained in 12/14 and 9/14, respectively, while absolute agreement was > 90% for most structures evaluated. Regarding the quantitative cardiac measurements, ICC values were above 0.90 for all but cardiac axis (intraobserver ICC, 0.81 and interobserver ICC, 0.61). There were no significant differences in the repeatability values observed for qualitative or quantitative parameters among the trimesters of pregnancy.

CONCLUSION

Cardiac examination from 4D-STIC volumes showed a high repeatability between and within observers in each trimester of pregnancy.

Nuchal translucency and cystic hygroma colli in screening for fetal major congenital heart defects in a series of 12,910 euploid pregnancies

OBJECTIVE

Many studies have shown that an increased nuchal translucency (NT) may be a good marker of fetal heart malformation, but the extent to which NT is suitable for identifying the population at risk remains unclear. We aimed to determine the value of NT measurement and of the presence of cystic hygroma colli in the screening of euploid fetuses for congenital heart defects (CHD).

METHODS

We carried out a retrospective analysis of 12 910 euploid pregnancies examined between January 1995 and August 2007 at our institution. The screening performance of NT measurements in identifying fetuses with CHD was assessed, with comparison between the use of cut-offs defined as absolute values, multiples of the median (MoM) and percentiles. The presence of cystic hygroma colli was also assessed in the prediction of CHD.

RESULTS

The incidence of major CHD was 3.4 per thousand (44/12 910). The sensitivity of NT measurement in screening for major CHD was 54.5% if the threshold was set at the 95(th) percentile, 45.4% if it was set at 3 mm, 27.3% for 3.5 mm, 50.0% for 1.5 MoM and 45.5% for 1.75 MoM. The false-positive rates for these thresholds were 8.4, 6.6, 1.7, 8.9 and 6.3%, respectively. The incidence of major CHD was 1.2% (10/813) in cases of thick NT (> 95(th) centile) and 4.3% (13/304) in cases of hygroma colli.

CONCLUSIONS

NT measurement during the first trimester is potentially useful for screening for fetal major CHD. Screening performance is consistent whether NT values are expressed as MoMs, percentiles or absolute values. The incidence of major CHD seems to be higher in cases of cystic hygroma colli.

The nuchal translucency and the fetal heart: a literature review

In this overview the current knowledge of the relationship between an increased nuchal translucency (NT) measurement and fetal heart structure and function in chromosomally normal fetuses is reviewed. Relevant pathophysiological theories behind the increased NT are discussed. Fetuses with an increased NT have an increased risk for congenital heart disease (CHD) with no particular bias for one form of CHD over another. This risk increases with increasing NT measurement. Although the NT measurement is only a modestly effective screening tool for all CHD when used alone, it may indeed be effective in identifying specific CHD "likely to benefit" from prenatal diagnosis. The combination of an increased NT, tricuspid regurgitation and an abnormal ductus venosus (DV) Doppler flow profile, is a strong marker for CHD. A fetal echocardiogram should be performed at 20 weeks' gestation in fetuses with an NT > or = 95th percentile but < 99th percentile. When the NT measurement is > or = 99th percentile, or when tricuspid regurgitation and/or an abnormal DV flow pattern is found along with the increased NT, an earlier echocardiogram is indicated, followed by a repeat scan at around 20 weeks' gestation. The resultant increased demand for early fetal echocardiography and sonographers with this special expertise needs to be planned and provided for.

Prevalence of increased nuchal translucency in fetuses with congenital cardiac disease and a normal karyotype

OBJECTIVES

Our aims were to estimate the prevalence of increased nuchal translucency in fetuses with a normal karyotype that were subsequently diagnosed with congenital cardiac disease on fetal echocardiography, and to assess whether there is a link between increased nuchal translucency and specific congenital cardiac malformations.

METHODS

We reviewed all patients referred to King's College Hospital and the Evelina Children's Hospital in London for fetal echocardiography between January 1998 and December 2007. We investigated the proportion of chromosomally normal fetuses with congenitally malformed hearts in which nuchal thickness was increased, both overall and with specific defects.

RESULTS

We identified 2133 fetuses with congenital cardiac disease by prenatal echocardiography. Of those, 707 were excluded due to abnormal karyotype, and 690 were excluded due to unknown karyotype. The remaining 736 were eligible for inclusion. Among 481 fetuses with documented congenital cardiac disease and normal chromosomes, making up 23% of the overall cohort, 224 had increased nuchal thickness defined as equal or greater than 2.5 millimetres, this being 0.47 of the inclusive cohort, with 95% confidence intervals from 0.42 to 0.51. These proportions were significantly higher than the expected proportion of the normal population, which was 0.05 (p < 0.001). The only diagnosis for which the proportion of fetuses with nuchal translucency measurement equal or greater than 2.5 millimetres was higher than the others was atrioventricular septal defect, with 0.62 of this cohort having abnormal values, with 95% confidence intervals from 0.47 to 0.77 (p = 0.038).

CONCLUSION

We found that nearly half of prenatally diagnosed fetuses with congenitally malformed hearts, when examined ultrasonically in the first or early-second trimester, had increased nuchal thickness. We recommend, therefore, referral of all fetuses with increased nuchal translucency for fetal echocardiography.