us e fetal

Ultrasound Obstet Gynecol 2012; 40: 418–425Published online 17 September 2012 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.10116

Barriers to prenatal detection of congenital heart disease:a population-based study

N. M. PINTO*, H. T. KEENAN†, L. L. MINICH*, M. D. PUCHALSKI*, M. HEYWOOD‡and L. D. BOTTO§*Division of Cardiology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA; †Division of CriticalCare Medicine, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA; ‡University of Utah School ofMedicine, Salt Lake City, UT, USA; §Division of Medical Genetics, Department of Pediatrics, University of Utah School of Medicine, SaltLake City, UT, USA

KEYWORDS: congenital heart disease; fetal; prenatal; ultrasound

ABSTRACT

Objective To evaluate the extent and determinants ofmissed prenatal detection of congenital heart disease(CHD) in a population-based setting.

Methods This was a retrospective cohort study of caseswith CHD, excluding minor defects, identified between1997 and 2007 by a statewide surveillance program.We examined a comprehensive list of potential risk fac-tors for which data were available in the surveillancedatabase from abstracted medical charts. We analyzedthe association of fetal, maternal and encounter factorswith 1) whether a prenatal ultrasound was performed and2) prenatal detection of CHD.

Results CHD was detected prenatally in only 39% of1474 cases, with no improvement in detection rate overthe 10-year period. Among the 97% (n = 1431) of moth-ers who underwent one or more ultrasound examinations,35% were interpreted as abnormal; fetal echocardiogra-phy was performed in 27% of the entire cohort. Maternaland encounter factors increasing the adjusted odds ofprenatal detection included: family history of CHD (OR,4.3 (95% CI, 1.9–9.9)), presence of extracardiac defects(OR, 2.7 (95% CI, 1.9–3.9)) and ultrasound location i.e.high risk clinic vs clinic (OR, 2.1 (95% CI, 1.3–3.1)).Defects that would be expected to have an abnormaloutflow-tract view were missed more often (64%) thanwere those that would be expected to have an abnormalfour-chamber view (42%).

Conclusion The majority of CHD cases over the 10-year study period were missed prenatally and detectionrates did not increase materially during that time. Thefailure to detect CHD prenatally was related to encountercharacteristics, specifically involving screening ultrasoundexaminations, which may be targeted for improvement.

Copyright 2012 ISUOG. Published by John Wiley &Sons, Ltd.

INTRODUCTION

Congenital heart disease (CHD) is one of the most com-mon and lethal birth defects1. Approximately 1% ofliveborn infants have CHD. Of these, 18% die withina year2 and 40% require some type of intervention3.CHD diagnosis prior to delivery allows for early parentalcounseling. Although data regarding the impact of prena-tal diagnosis of CHD on mortality are conflicting4–8, itis widely accepted that for prenatally diagnosed infantsrequiring intervention, planned delivery and appropri-ate postnatal care improve preoperative hemodynamicstability, decreasing perioperative morbidity5,9.

Efficient screening for fetal CHD is challenging,requiring a population-based approach, as most casesoccur in mothers without known risk factors10,11.Consensus recommendations in the USA advocate CHDscreening during standard second-trimester ultrasoundexamination, using a four-chamber view of the fetalheart, plus, if ‘technically feasible’, an outflow-tractview12,13. Published studies report detection rates forCHD as high as 55–65% with the four-chamber viewalone and 80–84% with the addition of the outflow-tract view14,15. However, current screening practices inmost developed countries detect only 30–50% of CHDcases2,11,16,17. While low rates of prenatal detection arewell documented16–18, the reasons for failed detectionhave not been well studied.

Several studies cite low rates of prenatal CHD detectioneven when > 90% of women in the population undergofetal ultrasound examination14,16,17,19–21. Therefore, fac-tors other than low use of prenatal ultrasound, includinggestational age at the time of ultrasound, maternal habi-tus, technical ability to obtain appropriate views, CHD

Correspondence to: Dr N. M. Pinto, 100 N. Mario Capecchi Drive, Salt Lake City, UT 84113, USA (e-mail: [email protected])

Accepted: 30 September 2011

Copyright 2012 ISUOG. Published by John Wiley & Sons, Ltd. ORIGINAL PAPER

Prenatal detection of CHD 419

diagnosis and the ultrasound operator’s and reader’s expe-rience, likely play a greater role in CHD detection. Studiesof predictors of failed CHD detection have been per-formed in select cohorts20,22. However, we are unaware ofany systematic population-based study of the potentiallymodifiable factors related to failed detection.

We used population data from the Utah Birth DefectNetwork (UBDN) to: 1) determine the rate of failedprenatal detection of CHD, 2) determine when duringpregnancy the opportunity to detect CHD is missed, and3) identify maternal and encounter-related risk factors forfailed prenatal detection.

METHODS

Cases

This retrospective cohort study included all cases of majorCHD identified by the UBDN from 1997 to 2007 for alllive births, stillbirths and terminations at > 20 weeks’gestation. We excluded cases with only isolated septaldefects (except for inlet-type ventricular septal defects) ormild valve abnormalities (isolated stenosis or regurgita-tion without associated ventricular chamber hypoplasia).Inlet ventricular septal defects were included as most canbe seen on an appropriate four-chamber screening viewat the level of the atrioventricular valves (while outflowtract or perimembranous defects may be missed) and mostwill require postnatal intervention. Cases of severe val-var stenosis with associated ventricular hypoplasia wereincluded as these again should be seen on a four-chamberscreening view and in these cases intervention is almostalways required. Cases were reviewed and then codedusing the Center for Disease Control recommended mod-ified ICD-9-DM codes23. If the case had multiple CHDcodes, it was assigned a primary diagnosis based onthe most significant defect. For each case we determinedwhich, if any, ultrasound view would be expected to beabnormal at screening, according to the particular defectspresent. If a case had multiple defects, all defects andtheir expected abnormalities on screening images wereused to designate them as either an ‘expected abnor-mal four-chamber screening view’, ‘expected abnormaloutflow-tract view’, ‘expected abnormal both views’ or‘expected abnormal neither view’.

Data source

The UBDN is a well-established, robust population-basedstatewide surveillance system that meets the requirementsof the Centers for Birth Defects Research and Preven-tion methodology and participates in the National BirthDefects Prevention Study. The UBDN, under the auspicesof the Utah Department of Health, prospectively monitorsall births (live births, stillbirths and pregnancy termina-tions) of mothers who reside in Utah to identify majorbirth defects. Age at first diagnosis is up to 24 months.The UBDN has over 100 data sources, resulting in a highlevel of case ascertainment. Potential cases are reviewed

by three medical geneticists (including one who is alsoboard-certified in maternal–fetal medicine (MFM)). MostCHD cases are also reviewed by a pediatric cardiolo-gist. The UBDN began collecting CHD data in 1997 forconotruncal and left-sided obstructive lesions. In 1999,ascertainment expanded to include all heart defects withthe exception of isolated ventricular septal defects, whichwere included from 2003. The database includes detailedinformation regarding maternal characteristics, prenatalcare and imaging and postnatal diagnosis and imaging.

Data collection

Maternal and encounter characteristics were collectedfrom the UBDN database. A positive family history wasdefined as a history of CHD in a first-degree relative.Ultrasound reader was defined in a hierarchical fashionin the order in which referrals would typically be made.Thus, cases in which multiple ultrasound examinationshad been performed and interpreted by obstetriciansand/or radiologists and MFM specialists were coded asread by a MFM; those in which ultrasound examinationshad been interpreted by obstetricians and radiologistswere coded as read by a radiologist; those in whichthey were interpreted only by obstetricians were codedas read by an obstetrician. Location of ultrasoundexamination was treated in a similar hierarchical fashion,with high-risk clinics, followed by hospitals and thengeneral clinics. We defined a screening ultrasound asthe first ultrasound examination performed between16 and 24 weeks’ gestation, as this is when anomalyscreening is performed. Cases delivered in 2003–2007were reviewed for available prenatal ultrasound reports.Though data from ultrasound reports, including timing,location, reader and diagnoses, had been abstracted forall cases, paper reports were not retained prior to 2003.Reports were reviewed solely for detailed documentationregarding the cardiac screening views obtained andwhether they were read as normal or abnormal. Paperreports were not used as a source for other study variables.

Additional socioeconomic variables and measuresof distance were obtained from the 2000 censusdata using the University of Utah’s Department ofGeography’s Digitally Integrated Geographic InformationTechnologies (DIGIT) lab. Using the maternal addressat delivery, the DIGIT lab provided census-tract levelmeasures of socioeconomic status, including education,median income and population below the poverty level(defined by the Census bureau for family size and numberof dependents24). Census-tract rural-urban commutingareas were used to define residence as ‘urban’ (codes1–3) or ‘rural’ (codes 4–10)25. Travel time to the nearestpediatric hospital with a fetal cardiology program wascalculated using distance and road speed data, with amaximum speed of 55 mph.

Statistical analysis

The cohort was described using frequencies and propor-tions. Odds ratios were used to examine the association of

Copyright 2012 ISUOG. Published by John Wiley & Sons, Ltd. Ultrasound Obstet Gynecol 2012; 40: 418–425.

420 Pinto et al.

fetal, maternal and encounter factors with documentationof having undergone a prenatal ultrasound examinationand prenatal diagnosis of CHD. Logistic regression wasused to model risk factors for undergoing a prenatalultrasound examination and detection of CHD. Covari-ates were included in the model if on univariate analysisP < 0.2. Models were examined for collinearity and, iffound, the variable with the strongest association wasretained. Log likelihood ratios were used to backwardseliminate covariates. All analyses were conducted usingStata 11.0 (StataCorp, College Station, TX, USA).

The study was approved by the institutional reviewboards of the University of Utah and the Utah Departmentof Health.

RESULTS

There were 1474 cases of CHD ascertained by the UBDNin 1997–2007 that met our study inclusion criteria; theircharacteristics are given in Table S1. The number of casesof CHD was lower in 1997–1998, when only conotruncaland left-sided obstructive heart lesions were collectedby the UBDN, but stable through the rest of the studyperiod. Most mothers were white and had an educationat high-school level or lower. A family history of CHDwas reported in 3% of cases. Extracardiac malformationswere present in 38% of cases and 1% had heterotaxy.

The majority of mothers (87%) had their first prenatalvisit in the first trimester. About half (53%) of the cohorthad prenatal ultrasound examinations performed only ina clinic (family practice or obstetric), 32% had one ormore ultrasound examinations performed in a hospitaland 15% had one or more performed in a MFM clinic.The interpreting physician’s specialty could be identified in690 (47%) cases. For screening ultrasound examinations,62% were read by an obstetrician, 12% by a radiologistand 25% by a MFM.

Rate of prenatal detection

The proportion of CHD cases detected prenatally in thiscohort was 39% (574/1474), with no significant differ-ences according to year of delivery (Figure 1, P = 0.10).The lowest detection rates (Figure 2) were for aortopul-monary windows (0%) and total anomalous pulmonaryvenous return (6%). Detection was also low for conotrun-cal or outflow tract anomalies, including truncus arterio-sus (24%), tetralogy of Fallot with pulmonary stenosis(26%) and transposition of the great arteries (14%).

Missed opportunity for CHD detection

Almost all (97%) mothers of CHD cases underwent atleast one prenatal ultrasound examination and 77%had an ultrasound exam between 16 and 24 weeks’gestation. However, 60% of CHD cases in which aprenatal ultrasound examination had been performedwere missed. Fetal echocardiograms were performed in

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Figure 1 Rate of prenatal detection of congenital heart defects(CHD) from 1997 to 2007 in the state of Utah. There was nosignificant difference in detection according to birth cohort year(P = 0.10). *Figures in 1997 and 1998 represent only conotruncaland left obstructive types of CHD. , defects detected; , defectsmissed.

27% of CHD cases. Family history of CHD was associatedwith having undergone a fetal echocardiogram (65% vs47%, P = 0.02). However, 35% of mothers with a familyhistory of CHD did not receive a fetal echocardiogram.Although most (89%) cases with an abnormal ultrasoundwere seen by a MFM, 42% of these cases never had a fetalechocardiogram. Of those with a fetal echocardiogram,3% had a missed CHD diagnosis, predominantlycoarctation of the aorta (n = 8), with one case each ofdouble outlet right ventricle and double inlet left ventricle.

Factors related to undergoing an ultrasoundexamination

Factors associated with failure to receive a prenatalultrasound examination included later initiation ofprenatal care, higher number of previous pregnancies andmaternal residence in a census tract in which 10–20%of the population were below the poverty level; they didnot include maternal age, education or race (Table 1). Inthe multivariate model, only late initiation of prenatalcare (in second trimester: odds ratio (OR), 0.35 (95%CI, 0.12–0.976) and in third trimester: OR, 0.1 (95%CI, 0.0–0.4)) was associated independently with failureto undergo prenatal ultrasound.

Risk factors related to missed CHD diagnosis

Among mothers who underwent ultrasound examination,maternal factors associated with lower prenatal detectionof CHD included younger age, fewer years of education,excessive weight gain during pregnancy (> 16 kg (c. 35lb)) and rural residence (Table 1). In contrast, a familyhistory of CHD increased the odds of prenatal detection(OR, 2.1 (95% CI, 1.2–3.7)).

Encounter factors associated with lower prenataldetection of CHD included ultrasound examinationsperformed solely at general clinics compared with oneor more performed at a hospital or MFM clinic (Table 2).Nevertheless, 67% of CHD cases which underwent



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ultrasound examination in a hospital and 25% in aMFM clinic were missed. Another factor related to lowerdetection was travel time to the nearest fetal cardiologyprogram (per additional hour of travel: OR, 0.9 (95% CI,0.78–0.97)). CHD cases without additional non-cardiacdefects were less likely to be diagnosed prenatally (56%vs 29%, P < 0.001).

Defects were categorized based on the screening view(s)expected to be abnormal (Figure 2). If a case had multiple

defects, all expected abnormal views (in addition to theirprimary diagnoses) were considered. Compared withdefects for which neither view would be expected tobe abnormal, those with an expected abnormal four-chamber view had the highest chance of being detectedprenatally (OR, 4.6 (95% CI, 3.6–5.7)), while thosewith an isolated expected abnormal outflow-tract viewhad a slightly increased likelihood of detection (OR, 1.8(95% CI, 1.4–2.4)). However, 42% of cases with an


422 Pinto et al.

Table 1 Maternal characteristics associated with undergoing ultrasound examination (US exam) and prenatal detection of congenital heartdisease (CHD) in Utah between 1997 and 2007

US exams received Prenatal detection of CHD

Characteristic n (%)* OR (95% CI) n (%)† OR (95% CI)

Maternal age≥ 35 years 197 (96) 1 96 (49) 121–34 years 1096 (97) 1.61 (0.76–3.44) 430 (39) 0.51 (0.32–0.80)< 21 years 138 (98) 2.10 (0.56–7.90) 45 (33) 0.68 (0.50–0.92)

Plurality Collinear (—) 1.45 (0.93–2.41)Singleton gestation 1360 (97) 536 (39)Multiple gestation 71 (100) 35 (49)

Initiation of prenatal careFirst trimester 1400 (98) 1 488 (35) 1Second trimester 135 (96) 0.35 (0.13–0.98) 55 (41) 1.04 (0.73–1.49)Third trimester 38 (90) 0.12 (0.04–0.39) 11 (29) 1.03 (0.63–1.69)

GravidityPer additional pregnancy 0.89 (0.79–1.00) 1.10 (1.04–1.15)

Maternal BMI at first visit< 25 kg/m2 838 (97) 1 340 (41) 1≥ 25 kg/m2 320 (98) 0.95 (0.73–1.24) 126 (39) 0.95 (0.73–1.23)≥ 30 kg/m2 273 (96) 0.91 (0.69–1.20) 105 (38) 0.90 (0.69–1.19)

Weight gain≤ 16 kg (c. 35 lb) (normal) 419 (42) 1> 16 kg (c. 35 lb) (excessive) 152 (35) 0.72 (0.58–0.91)

Maternal educationCollege graduate 169 (95) 1 87 (51) 1High school 633 (98) 2.14 (0.88–5.19) 249 (39) 0.56 (0.40–0.78)< High school 629 (97) 1.41 (0.62–3.28) 235 (37) 0.62 (0.44–0.86)

Family history 49 (98) 1.49 (0.20–11.04) 28 (57) 2.06 (1.16–3.66)Maternal race

White 1191 (97) 1 464 (39) 1Non-white 234 (97) 0.93 (0.40–2.12) 103 (44) 1.23 (0.93–1.64)

Census-tract level % of adults ≥ 25 yearswith < high school education0.0–14.9% 952 (97) 1 387 (41) 115.0–24.9% 314 (97) 0.86 (0.41–1.79) 111 (35) 0.79 (0.61–1.02)25.0–39.9% 99 (96) 0.68 (0.23–1.98) 41 (41) 1.00 (0.66–1.51)40.0–100.0% 24 (96) 0.66 (0.09–5.03) 13 (54) 1.64 (0.74–3.63)

Census-tract level % of adults ≥ 25 yearswith college degree40.0–100.0% 176 (98) 1 74 (42) 125.0–39.9% 387 (96) 0.41 (0.12–1.43) 171 (44) 1.02 (0.72–1.46)15.0–24.9% 484 (98) 0.69 (0.19–2.46) 173 (36) 0.75 (0.53–1.06)0.0–14.9% 342 (97) 0.58 (0.16–2.14) 134 (39) 0.85 (0.59–1.23)

Census-tract level % below poverty level‡0.0–4.9% 516 (98) 1 211 (41) 15.0–9.9% 437 (98) 0.93 (0.39–2.21) 169 (39) 0.90 (0.69–1.17)10.0–19.9% 277 (94) 0.32 (0.15–0.70) 112 (40) 0.92 (0.69–1.23)20.0–100.0% 159 (99) 1.7 (0.37–7.72) 60 (38) 0.88 (0.61–1.27)

Census-tract level rural residence§Urban 1247 (97) 1 506 (41) 1Rural 142 (96) 0.66 (0.27–1.61) 46 (32) 0.69 (0.78–0.99)

*Proportion of the cohort who underwent an ultrasound examination. †Proportion of cases detected out of those who underwent anultrasound examination. ‡Defined by the Census bureau for family size and number of dependents24. §Census-tract rural-urban commutingareas were used to define residence as ‘urban’ (codes 1–3) or ‘rural’ (codes 4–10)25. BMI, body mass index.

expected abnormal four-chamber view, 64% with anexpected abnormal outflow-tract view and 30% withboth views expected to be abnormal were not detectedprenatally.

On multivariate analysis, after adjusting for maternalrace and rural residence, prenatal detection was relatedindependently to several encounter factors, including

total number of fetal ultrasound examinations, locationof ultrasound examination and an abnormal screeningultrasound result (Table 3). Cases with a family history ofCHD and those with an additional non-cardiac congenitaldefect had higher odds of prenatal detection. Maternalage, education and weight gain during pregnancy werenot retained in the final model.



Table 2 Encounter factors related to prenatal detection ofcongenital heart disease (CHD) identified in Utah between 1997and 2007 when a prenatal ultrasound (US) examination had beenperformed

Characteristic

CHDdetected(n (%)) Odds ratio (95% CI)

US locationClinic 164 (22) 1Hospital 65 (31) 1.60 (1.14–2.25)MFM/high-risk clinic 341 (74) 10.00 (7.64–13.10)

US interpreterObstetrician 18 (6) 1Radiologist 10 (16) 2.77 (1.21–6.32)MFM 268 (79) 56.41 (32.7–97.2)

US outcomeNormal 93 (11) 1Suspected abnormality 74 (75) 24.38 (14.75–40.27)Abnormal 398 (86) 52.03 (36.96–73.24)

Screening US location*Clinic 191 (28) 1Hospital 59 (38) 1.60 (1.14–2.25)MFM/high-risk clinic 211 (71) 10.00 (7.64–13.10)

Screening US interpreter*Obstetrician 116 (32) 1Radiologist 36 (50) 2.77 (1.21–6.32)MFM 110 (75) 56.41 (32.7–97.2)

Number of US exams 1.79 (1.65–1.93)(per additional exam)

Presence of additionalcongenital defects

311 (57) 3.18 (2.55–3.98)

Presence of heterotaxy 12 (60) 2.29 (0.92–5.63)Travel time to fetal

cardiology program0.90 (0.78–0.97)

(per additional hour)

*Screening US is first US exam performed between 16 and 24weeks. MFM, maternal–fetal medicine specialist.

Table 3 Multivariate regression model for prenatal detection ofcongenital heart disease

Odds ratio (95% CI) P

Maternal characteristicsPlurality 0.5 (0.2–0.9) 0.04Family history 4.3 (1.9–9.9) < 0.01Maternal rural residence 0.6 (0.3–1.2) 0.14

Encounter characteristicsEach additional US exam 1.6 (1.4–1.7) < 0.01Suspected abnormality on US 17.3 (9.8–30.5) < 0.01Abnormal US 31.3 (20.7–47.6) < 0.01Additional congenital defect 2.7 (1.9–3.9) < 0.01US performed at high-risk clinic 2.1 (1.3–3.1) < 0.01US performed at hospital 0.8 (0.4–1.3) 0.31

US, ultrasound.

Subset analysis

Of the 705 cases delivered after 2003, 297 (42%) hadultrasound reports available for review. Compared withthe whole cohort (n = 1474), this subset of patients hada higher rate of prenatal detection (79%). The review oftheir reports showed that 95% had documented cardiac

screening, including 65% with specific documentationof a four-chamber view and 57% with documentationof both four-chamber and outflow-tract views. A fetalechocardiogram was never performed in 10% of casesthat documented an abnormal cardiac screen.

DISCUSSION

This study is the first in 15 years to provide data onlongitudinal trends in prenatal detection of CHD in theUSA. It also provides novel population-based findings onpotential predictors of missed prenatal detection of CHD.Utilizing a statewide birth defect surveillance system, weexamined a comprehensive list of potential risk factorsnot readily available in previous population studies ofprenatal CHD detection. We found that the majority ofCHD cases were missed prenatally and that detectionrates did not increase materially over the 10-year studyperiod. Although discouraging, the findings also suggestmissed opportunities in the screening process that couldbe targeted to improve CHD detection.

The low rate of prenatal detection (39%) in ourcohort of approximately 1500 patients is consistent withprevious national and European publications14,16,17,19–21.The finding that CHD detection rates did not improvesignificantly over the 10-year study period (1997–2007)is in contrast to an earlier population study in Atlanta26.However, in that study the initial rate of detection wasvery low (2.6%), and the study period overlapped with theperiod of rapid evolution of fetal ultrasound technologyin the 1990s. Nevertheless, the lack of improvement inprenatal detection rates in our more recent time period isconcerning and emphasizes the importance of identifyingmodifiable factors that, if appropriately targeted, couldincrease the sensitivity of current screening approaches.

Similar to previous studies14,16,17,19–21, we found thatfetal ultrasound use was nearly universal. Thus, increasingthe rates of screening alone is unlikely to improve CHDdetection. The major risk factor for missed CHD detectionwas failure to detect a cardiac abnormality on routineultrasound, particularly for defects expected to have onlyan abnormal outflow-tract view. Potentially, interventionsaimed at improving the skills of those performing andreviewing prenatal screening ultrasound examinationscould increase the detection of serious cardiac anomalies,including many conotruncal malformations.

Opportunities for CHD detection may also have beenmissed because some mothers did not receive higher levelimaging. Thirty-five percent of mothers with a familyhistory of CHD and 10% of those with abnormal cardiacfindings on screening ultrasound did not receive a fetalechocardiogram. While some patients may have beenreferred to MFM clinics first, evidence suggests thatevaluation by a MFM specialist alone is insufficient whensuspicion for CHD is increased by risk group or anabnormal screen27. In our study, 25% of patients scannedat a MFM office had a CHD that went undetected.

Potential risk factors for failed prenatal CHD detec-tion include sociodemographic factors and factors that


424 Pinto et al.

affect image quality, such as maternal body habitus.Studies examining sociodemographic factors show con-flicting results20,22. In our study, neither individual norgeographic measures of socioeconomic status were associ-ated with prenatal CHD detection. This lack of associationmay be related to the current nearly universal use ofultrasound. We also did not observe an independent asso-ciation of any maternal factor, such as body habitus, withCHD detection.

The primary risk factors for missed prenatal CHDdetection were fetal ultrasound location, ultrasoundinterpreter and absence of extracardiac malformations.Most heart defects are isolated, with no extracardiacanomalies to increase suspicion. Additionally, mostpatients received their screening ultrasound in low-riskoutpatient settings, where detection rates are lowercompared to tertiary or university-based settings20,22.The effects of location and interpreter are likely dueto variations in experience, training, and equipment. Thisstudy was not designed to explore these factors. However,even in best-case scenarios, among mothers who had oneof more ultrasound examinations performed at a MFMclinic and interpreted by a MFM, a quarter of significantCHD was missed prenatally.

Prenatal CHD detection was lower for those cases withan expected abnormal outflow-tract view than for thosewith an expected abnormal four-chamber view (of which40% were still missed). This is consistent with otherstudies16,18,20,22,28,29. The addition of an outflow viewsignificantly enhances prenatal CHD detection, yet itssuccessful visualization is inconsistent and not uniformlyrequired30,31. Currently, these views are not mandatory inrecommendations for cardiac screening in the USA12,13,although standardizing cardiac screening protocols andenhancing training could improve the ability to obtainthis difficult view and improve detection rates28,29,32–35.In the UK and Canada, the routine assessment of outflowtracts is already part of the guidelines for screening36,37.

This study had some limitations. It used data obtainedfor surveillance purposes; miscoding or data entry errorscould have been present. Miscoding is unlikely, sinceall UBDN CHD cases undergo clinical review by apediatric geneticist specializing in CHD or a pediatriccardiologist. Utah is predominately Caucasian, whichdecreases our study’s generalizability, although our resultsconfirm findings reported in other regions of the country.We were also unable to determine whether the lackof indicated fetal echocardiograms was due to a lackof referral or due to referred patients not actuallyhaving a fetal echocardiogram. The analysis of ultrasoundreports must be interpreted with caution since only aminority of patients (those with a higher rate of prenataldetection) had reports available for review. Finally, inusing secondary data, we were unable to review screeningimages directly. This will be important in future researchto generate additional insights into prenatal detection.

In conclusion, in spite of nearly universal ultrasoundscreening, most (61%) significant CHD in this cohortwas missed prenatally. Our study identified multiple

points in the screening process amenable to improvement.The one likely to have the largest population effect isimprovement to the initial screen done in the low-riskoutpatient setting. The scarce improvement in detectionrates over the recent decade suggests that initiatives toenhance the screening process have been neither effectivenor widely disseminated. Since the primary risk factors forfailed detection of CHD appear to be related to screeningmethods, targeted strategies amenable to widespreadadoption in clinical practice may improve detection. Thefailure to detect these defects prenatally represents amissed opportunity to provide counseling and timely carefor infants with CHD.

ACKNOWLEDGMENTS

We would like to thank Professor Paula Woodward,MD, of the Department of Radiology, University of UtahSchool of Medicine and Professor Michael Varner, MD,of Maternal Fetal Medicine, Department of Obstetricsand Gynecology, University of Utah School of Medicinefor their review and input on this paper. This study wassupported in part by the Children’s Health ResearchCenter, University of Utah as well as by an NIHInstitutional Career Enhancement Award for Dr Pinto(1KM1CA156723-01).

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SUPPORTING INFORMATION ON THE INTERNET

The following supporting information may be found in the online version of this article:

Table S1 Demographics and descriptors of cases of congenital heart disease identified in Utah between1997 and 2007


us e fetal

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