Screening for congenital heart defects by transabdominal ultrasound - role of early gestational screening and importance of operator training

Incremental Detection of Severe Congenital Heart Disease by Fetal Echocardiography Following a Normal Second Trimester Ultrasound Scan in Québec, Canada

Background:

The benefit of fetal echocardiograms (FE) to detect severe congenital heart diseases (SCHD) in the setting of a normal second-trimester ultrasound is unclear. We aimed to assess whether the increase in SCHD detection rates when FE are performed for risk factors in the setting of a normal ultrasound was clinically significant to justify the resources needed.

Methods:

This is a multicenter, population-based, retrospective cohort study, including all singleton pregnancies and offspring in Quebec (Canada) between 2007 and 2015. Administrative health care data were linked with FE clinical data to gather information on prenatal diagnosis of CHD, indications for FE, outcomes of pregnancy and offspring, postnatal diagnosis of CHD, cardiac interventions, and causes of death. The difference between the sensitivity to detect SCHD with and without FE for risk factors was calculated using generalized estimating equations with a noninferiority margin of 5 percentage points.

Results:

A total of 688 247 singleton pregnancies were included, of which 30 263 had at least one FE. There were 1564 SCHD, including 1071 that were detected prenatally (68.5%). There were 12 210 FE performed for risk factors in the setting of a normal second-trimester ultrasound, which led to the detection of 49 additional cases of SCHD over 8 years. FE referrals for risk factors increased sensitivity by 3.1 percentage points (95% CI, 2.3–4.0; P<0.0001 for noninferiority).

Conclusions:

In the setting of a normal second-trimester ultrasound, adding a FE for risk factors offered low incremental value to the detection rate of SCHD in singleton pregnancies. The current ratio of clinical gains versus the FE resources needed to screen for SCHD in singleton pregnancies with isolated risk factors does not seem favorable. Further studies should evaluate whether these resources could be better allocated to increase SCHD sensitivity at the ultrasound level, and to help decrease heterogeneity between regions, institutions and operators.

The Mathematical Limitations of Fetal Echocardiography as a Screening Tool in the Setting of a Normal Second-Trimester Ultrasound

Background

The effectiveness of screening strategies targeting pregnancies at higher risk of congenital heart disease (CHD) is reduced by the low prevalence of severe CHD, the increase in CHD detection rates by second-trimester ultrasound (U/S), and the high proportion of severe CHD in low-risk pregnancies. We aimed to determine situations in which additional screening by fetal echocardiography (FE) would result in a significant increase in sensitivity and a sizable decrease in the false-negative rate of detection of severe CHD.

Methods

We simulated the change in the numbers of detected severe CHD cases when FE is offered to women with a normal second-trimester U/S who have a higher risk of bearing a child with CHD, compared to U/S alone. The primary outcome was the increase in sensitivity. Secondary outcomes were the number needed to screen and the reduction in the rate of missed cases.

Results

For an U/S sensitivity of 60%, the addition of FE in pregnancies at high risk of CHD (risk ratio 3.5; range: 2 to 5) increased sensitivity by 2.4 percentage points (1.1 to 7.9). The number needed to screen to detect one additional case of severe CHD was 436 (156 to 952). The rate of additional severe CHD cases detected by FE was 4 per 100,000 pregnancies (2 to 32).

Conclusions

The addition of FE to U/S for severe CHD prenatal screening in pregnancies at high risk of CHD yielded marginal benefits in terms of increased sensitivity and decreased rates of false negatives, at the expense of significant resource utilization.

Postmortem Assessment of Isolated Congenital Heart Defects Remains Essential Following Termination of Pregnancy

OBJECTIVES

To investigate the correlation between prenatal ultrasound (US) and autopsy findings in pregnancies terminated due to isolated congenital heart defects (CHDs), including CHDs associated with heterotaxy syndrome.

MATERIALS AND METHODS

The material consists of 67 fetuses with prenatally detected isolated CHDs or CHDs associated with heterotaxy syndrome at a tertiary center in Norway between 1985 and 2014. The main CHDs were categorized into subdiagnoses of CHDs in accordance with ICD-10. The US and autopsy findings were categorized according to degree of concordance.

RESULTS

Gestational age at termination was 12 + 0-22 + 6 weeks. Hypoplastic left heart syndrome was the most common main diagnosis among the 67 fetuses (32.8%). There was full agreement between US and autopsy findings in 97.4% (222/228) of all subdiagnoses. The discrepant findings in three fetuses had no influence on the decision to terminate the pregnancy.

CONCLUSIONS

The correlation was high between prenatal US and postmortem findings in fetuses with isolated CHDs. Meticulous assessment of cardiac anatomy is particularly necessary when the decision to terminate relies on isolated CHDs. The trend of earlier termination challenges verification of diagnoses at autopsy. Consequently, the fetus should be examined at a tertiary center with fetal medicine specialists, pediatric cardiologists and perinatal pathologists.

Feasibility and Accuracy of Early Fetal Echocardiography Performed at 13+0-13+6 Weeks in a Population with Low and High Body Mass Index: a Prospective Study

PURPOSE

The earlier the detection and diagnosis of congenital heart diseases (CHD), the greater the clinical benefit; however, early fetal cardiac examination can be a challenge. The aim of our study is to demonstrate that the fetal cardiac examination at 13⁺⁰-13⁺⁶ weeks can be as adequately assessed as the examination performed at 16 weeks in patients with low and high body mass index (BMI).

METHODS

The study was a prospective observational cohort study. One hundred pregnant women at low risk of congenital heart anomalies were divided into two groups: 49 women with low BMI (<25) and 51 women with high BMI (≥ 25). A complete fetal cardiac scan was performed on each patient at 13⁺⁰-13⁺⁶ weeks, via the transvaginal and transabdominal approaches, and at 16 weeks by the transabdominal approach.

RESULTS

The examination at 13⁺⁰-13⁺⁶ weeks was adequately assessed in at least one of the two routes in 97 patients, as opposed to 87 patients at 16 weeks. A significantly higher adequate assessment rate was obtained at 13⁺⁰-13⁺⁶ weeks than at 16 weeks (p=0.017). The transvaginal approach showed the best resolution of the three examinations in 42% of women with BMI ≥35. No CHD were overlooked.

CONCLUSIONS

Early fetal echocardiography is feasible and accurate at 13⁺⁰-13⁺⁶ weeks. Within patients with high BMI, early fetal echocardiography may be performed two weeks in advance, since it allows visualization of the fetal heart through the transvaginal route with a higher resolution in a large number of women, which is not feasible at 16 weeks.

Prenatal detection of congenital anomalies and related factors in Argentina

Congenital anomalies (CAs) are a leading cause of neonatal death. Many CAs can be diagnosed prenatally. To estimate the prenatal detection rate (PDR) of CA in hospitals participating in the RENAC (National Network of Congenital Anomalies of Argentina) and to analyze the PDR according to different factors. Sources were reports of RENAC from the 2013-2016 period. Congenital anomalies included were those detectable by ultrasound or by a prenatal karyotype. PDR was calculated by region, health subsector, clinical presentation, maternal age, sex, and twining. Using multiple logistic regression analysis, we evaluated predictors of prenatal detection. In total, 9976 cases were defined as prenatal detectable; 5021 were detected (PDR = 50.3%). Multiple presentation increased the chances of prenatal detection (Adj. OR = 1.6; 95%CI 1.4-1.9). Prenatal detection was lower in the public subsector (Adj. OR = 0.8; 95%CI 0.7-0.9) and in the northern regions of the country. PDR was higher than 75% in isolated cases of urinary malformation, anencephaly, and gastroschisis. Prenatal detection increased the chance of birth in higher complexity-level hospitals (Adj. OR = 2.5; 95%CI 2.3-2.8). PDR was within the range previously reported. Heterogeneity between regions and health subsector suggests the need for training to achieve equity in detection.

Rationale and Design of the FREQUENCY Study: The Fetal Cardiac Registry of Québec to Improve Resource Utilization in Fetal Cardiology

OBJECTIVE

Prenatal detection of congenital heart diseases (CHD) decreases morbidity and cost. To improve detections rates, most physicians refer pregnant women with high-risk pregnancies to fetal cardiologists even when there is no suspicion of CHD at the second trimester screening. This paper presents the rationale and detailed method of the Fetal Cardiac Registry of Québec to Improve Resource Utilization in Fetal Cardiology (FREQUENCY) study. The overall objective is to assess the impact of second trimester ultrasound screening (U/S) and referral pattern in fetal cardiology on detection rates, health care costs, and resource utilization, as well as perinatal morbidity and mortality.

METHODS

This multicentre retrospective population-based cohort study will link fetal echocardiography data from all centres performing fetal echocardiography in Québec with administrative health care data. This data linking will allow the determination of a true denominator (all women in Québec who underwent second trimester U/S) with complete follow-up of up to 2 years for offspring. This protocol meets Canadian Task Force Classification II-2.

RESULTS

The study investigators have collected and cleaned fetal echocardiography data for 24 259 eligible pregnancies referred to fetal cardiology. These data will be matched to approximately 860 000 pregnancies between 2007 and 2015.

CONCLUSION

The results of the FREQUENCY study will shed light on the impact of the current prenatal CHD screening strategy in Canada.

Early fetal ultrasound screening for major congenital heart defects without Doppler

OBJECTIVE

Congenital heart defects are the most common major structural fetal abnormalities. Color flow mapping has played a dominant role in the detection of abnormalities during the first trimester, regardless of the International Society of Ultrasound in Obstetrics and Gynecology warning on the use of Doppler during early pregnancy. The aim of our study was to investigate the use of transvaginal two-dimensional sonography without Doppler for assessing the four-chamber view and the outflow tract view of fetuses at 11-13 weeks of gestation for cardiac screening of major congenital heart defects.

STUDY DESIGN

This was a prospective observational study conducted in the Fetal Medicine Unit of Cabueñes University Hospital, between May 2014 and August 2015. Only low risk-pregnancies were studied. All ultrasonographic examinations were performed by two experienced sonographers in maternal-fetal medicine. The combination of high-frequency transvaginal (nine MHz) and transabdominal (six MHz) ultrasonography transducers were used. An early cardiac screening was performed in 97% of cases. Statistical analysis was carried out using successive multivariate logistic regression models in order to investigate the effect of crown-rump length and body mass index on the probability of visualizing the four-chamber view and/or the outflow tract view.

RESULTS

663 low-risk pregnant women were included. Regarding the transvaginal approach, neither the crown-rump length nor the body mass index had a statistically significant relationship on the probability of visualization of the four-chamber view and outflow tract view. For the transabdominal approach, the crown-rump length and the body mass index presented a statistically significant effect on the visualization of the four-chamber view and the outflow tract view. Using the transvaginal approach: the success rate of performing a four-chamber view was 89.4% and 82.4% for the outflow tract view. Using the transabdominal approach: the success rate of performing a four-chamber view was 77.8% and 61.5% for the outflow tract view. Four major congenital heart defects were diagnosed, and the prenatal ultrasonagraphic diagnosis was confirmed for all cases.

CONCLUSIONS

Routine first-trimester ultrasonagraphy without Doppler, when performed by experienced sonographers, can effectively identify major congenital heart defects. Additional multicenter well designed studies should clarify the feasibility of this approach.