Nuchal translucency and its relationship to congenital heart disease

Echocardiography in Early Pregnancy

Within the last decade, two significant events have contributed to the increasing interest in early fetal echocardiography. First, the introduction of high frequency vaginal ultrasound probes allows detailed visualization of cardiac structures at early stage of gestation, making early detection of fetal malformations possible. Second, the close relationship observed between some first trimester sonographic and Doppler markers and congenital heart defects allows an early identification of a high-risk group at 11 to 14 weeks of gestation. In this context, from the early 1990s, many authors have examined the potential role of the transvaginal approach to obtain earlier diagnosis of fetal cardiac malformations. Further studies have appeared in the literature showing that early transvaginal echocardiography in experienced hand is a fairly sensitive investigative tool. Although some malformations are detected as early as 11 weeks’ gestation, the optimal gestational age to perform the early scan is at least 13 weeks’ gestation. Transvaginal ultrasound is the preferred approach, although most of the authors agree that results can be improved if transabdominal ultrasound is also incorporated. The further application of color Doppler enhances visualization. The sensitivity and specificity of early fetal echocardiography for the detection of heart anomalies is acceptable compared to the ones obtained by mid-gestational echocardiography, showing a slight reduction in detection rates and an increase in false positive and negative rates. The cardiac anomalies detected at this early stage of pregnancy are mainly defects involving the four-chamber view, indicating that defects solely affecting the outflow tracts are difficult to diagnose in the first trimester of pregnancy. Heart defects diagnosed early in pregnancy tend to be more complex than those detected later, with a higher incidence of associated structural malformations, chromosomal abnormalities and spontaneous abortions. The neonate follow-up or postmortem examination in case of termination of pregnancy (TOP) is essential to assess the actual role of early fetal echocardiography. At present, early fetal echocardiography is a promising technique, which can be of considerable value for patients at high-risk. This technique is, however, currently limited to a few specialized centers.

The aim of this review is to explore the possibilities of examining the fetal heart at this early stage of pregnancy. This article also present our experience in the first multicenter trial in early fetal echocardiography performed in Spain. In accordance with other studies, this experience stresses the usefulness of early echocardiography when performed by expert operators on fetus specifically at risk for cardiac defects. Our review of these additional 48 cases contributes to the expanding literature on the ability of transvaginal ultrasonography to detect fetal heart defects in early pregnancy.

How to cite this article

Gabriel CC, Rodriguez PP. Echocardiography in Early Pregnancy. Donald School J Ultrasound Obstet Gynecol 2013;7(2):168-181.

Prenatal diagnosis of congenital heart disease

This article presents advancements in the field of fetal echocardiography and the significant impact of these within the fields of pediatric cardiology, perinatology, and neonatology. A prenatal diagnosis of congenital heart disease allows for improved counseling of the parents, guides the timing and optimal location of delivery, and allows appropriate planning and consultation between the cardiologist and neonatologist. It also facilitates accurate diagnosis and management of fetal arrhythmias, identifies potential candidates for in utero cardiac intervention, and serves as the imaging guidance technique for these procedures. The goals, indications, advantages, limitations, and spectrum of congenital heart disease that can be diagnosed are reviewed.

Is the nuchal index increased in fetuses with congenital structural heart defects?

OBJECTIVES

To determine if the Nuchal index (NIx) is increased in euploid fetuses with structural congenital heart defects (CHD).

METHODS

Euploid fetuses with CHD between 18 and 24 weeks gestation were identified. The next fetus meeting the same criteria with a normal fetal echocardiogram were selected as a control. The NIx [(mean nuchal thickness /mean biparietal diameter) x 100] and cardiac axis (CA; degrees) were calculated for each fetus. Standard descriptive tests and two-tailed t test were used.

RESULTS

The NIx in the abnormal (n = 20) and control (n = 20) groups were 9.10 (2.35) and 7.54 (p = 0.04) and CA was 55.8 degrees and 48.6 degrees (p = 0.02), respectively.

CONCLUSIONS

The NIx and CA were significantly different in fetuses with CHD. A prospective study to confirm these findings and determine clinical utility is warranted.

Utility of fetal echocardiogram in high-risk patients

AIM

Patients at high risk of fetal congenital heart disease are commonly referred for second trimester fetal echocardiogram. The objective of this study was to evaluate the utility of routine fetal echocardiogram in high-risk patients after the evaluation of the four-chamber/left ventricular outflow tract (LVOT) views during comprehensive second trimester anatomy ultrasound.

METHODS

Second trimester comprehensive anatomy ultrasounds, which included a four-chamber/LVOT view, and subsequent fetal echocardiograms carried out at the Duke University Medical Center from January 1995 and July 2002 were reviewed. Those fetal echocardiograms carried out between 17 and 30 weeks gestation were included in the analysis.

RESULTS

A total of 725 individual subjects met the inclusion criteria. Twenty-nine fetal echocardiograms were ultimately reported as abnormal. Of these, 19 had an abnormal four-chamber/LVOT view, four had a suboptimal view and six had a normal view. Of the six patients with a normal four-chamber/LVOT, all had been referred for echocardiogram based on the presence of other significant fetal anomalies noted at the time of second trimester anatomy ultrasound (3), documented aneuploidy (2), and significant fetal arrhythmia (1).

CONCLUSION

Utility in carrying out fetal echocardiogram was seen in patients with an abnormal four-chamber/LVOT view, a suboptimal view in a high-risk patient, and the presence of other significant fetal abnormalities. Utility was not seen in patients with pre-existing diabetes mellitus.

Latest advances and topics in fetal echocardiography

PURPOSE OF REVIEW

Fetal diagnosis and the supporting specialties of perinatology, neonatology, and surgery have made rapid strides in the last decade. Numerous centers are focusing on this multifaceted niche area as the medical field realizes its vast promise and potential. The authors review some of the major advancements in thought and practice in the field of fetal echocardiography while attempting to give a less detailed overview for the less involved perinatologist.

RECENT FINDINGS

First trimester fetal echocardiography has been an area of recent interest as transducer technology improves. As a result, optimum timing of first and subsequent scans and the population profile they are to be applied to have become an issue that begs consensus. Three-dimensional and four-dimensional fetal echocardiography have also received a boost for the same reasons, and both are being studied for feasibility and accuracy. Fetal tissue Doppler and spectral Doppler imaging are potential areas for exploration; the early steps have been taken. Awareness of associated ultrasound markers, such as exaggerated nuchal translucency, as clues to the presence of congenital heart disease is important, even if controversial.

SUMMARY

The issue of missed prenatal diagnosis is disturbing, especially when it arises against a background of tremendous skill and technologic support. Strategies to minimize mistakes in this critical aspect need to be agreed on by the involved teams and put in place in a multidisciplinary manner if they are to have an important impact.

Changing indications for fetal echocardiography in a University Center population

OBJECTIVES

We hypothesized that increased facility with fetal echocardiographic diagnosis by obstetricians is associated with changes in its indications and yields.

METHODS

We reviewed 300 fetal echocardiograms (December 2002-August 2003) and compared our findings with previous studies.

RESULTS

Mean maternal age was 31 +/- 6 (range 16-44) years. Gestational age was 24 +/- 5 weeks (mean +/- SD; median 22, range 15-38). Indications for fetal echocardiography included family history of congenital heart disease (CHD) (23%), maternal diabetes (18%), obstetrical scan suspicious for CHD (13%), arrhythmia (12%) maternal rheumatologic disease (7%), extracardiac congenital anomalies (6%), chromosomal anomaly (6%) and exposure to a potential fetal teratogen (5%). High yield indications included chromosomal anomaly (47%) and a suspicious obstetrical scan (42%). Low yield indications included family history of CHD (4%) and teratogen exposure (0%). 1/7 of the patients with increased nuchal translucency had pulmonary atresia/intact ventricular septum. No anomalies were associated with the single umbilical artery.

CONCLUSION

Indications and yields of fetal echocardiography have changed over the last decade. The frequency of an obstetrical scan suspicious for CHD has increased 2.5 to 3 times over a decade and continues to have high yield. Thus, increasing prenatal detection of CHD depends, to a large extent, on increasing the skills of obstetricians.

Jugular vein and carotid artery blood flow in fetuses with increased nuchal translucency at 10-14 weeks' gestation

OBJECTIVE

The aim of our study was to obtain measurements of the jugular vein and carotid artery pulsatility index (PI) at 10-14 weeks' gestation in chromosomally normal and abnormal fetuses with or without increased nuchal translucency (NT), in order to explore whether a relationship exists between increased NT and overperfusion of the head.

METHODS

This was a prospective study involving 179 pregnant women at high risk for chromosomal anomalies or structural malformations who were referred for chorionic villus sampling or first-trimester ultrasound examination at 10-14 weeks' gestation, respectively. Color and pulsed Doppler ultrasound were used to obtain jugular vein and carotid artery blood flow velocity waveforms at the level of the mid-neck. All Doppler measurements were obtained by a single investigator. The PIs of the jugular vein and carotid artery were correlated with NT measurement and fetal karyotype.

RESULTS

Doppler measurements of the jugular vein and carotid artery were successfully obtained in 90.5% of the fetuses. The fetal karyotype was abnormal in 13 cases, including three trisomies 21 and two trisomies 18, and normal in 149 cases. In the group with normal karyotype the NT was above the 95th percentile in 22 cases (15%). No correlation between the jugular vein or the carotid artery PI and the thickness of the NT was found. There were no significant differences when comparing the values of the jugular vein and carotid artery PI between the group with normal NT and the group with increased NT, or between the group with a normal karyotype and an abnormal karyotype.

CONCLUSION

Our results suggest that NT is not related to blood flow impedance in either the carotid artery or the jugular vein. Overperfusion and venous congestion of the head do not appear to be a causative pathophysiological mechanism involved in increased NT.

Prenatal diagnosis of hypoplastic left heart syndrome and trisomy 18 in a fetus with normal nuchal translucency and abnormal ductus venosus blood flow at 13 weeks of gestation

We describe a case of early prenatal diagnosis of a major congenital heart anomaly and trisomy 18 in a low-risk pregnant woman. Nuchal translucency (NT) measurement at 13 weeks' gestation was 1.2 mm and Doppler evaluation of the ductus venosus detected a persistent reversed flow during atrial contraction. This finding prompted us to perform fetal echocardiography which showed hypoplastic left heart syndrome. Karyotyping following chorionic villus sampling diagnosed trisomy 18. Review of the recent literature suggests that the finding of an abnormal ductus venosus Doppler pattern in the late first trimester of pregnancy may be an early sign of either congenital cardiac or chromosomal abnormality, even in the presence of normal NT screening.

Pregnancy outcome of embryonic/fetal pleural effusion in the first trimester

OBJECTIVE

To investigate the incidence of embryonic/fetal pleural effusion in the first trimester and its pregnancy outcome.

METHODS

A total of 965 viable singleton pregnancies confirmed by sonography between 7 and 10 weeks were examined to estimate the incidence of embryonic/fetal pleural effusion. When initial transvaginal sonography showed pleural effusion, serial ultrasound examinations were performed.

RESULTS

Pleural effusion was detected in 12 pregnancies (incidence, 1.2%; 95% confidence interval, 0.7-2.2), which involved bilateral thoracic cavities in all cases. The pregnancy outcome was assessed among 14 cases of pleural effusion, including 2 previously reported cases from the same institution. Among these, 12 pregnancies (86%) miscarried by 14 weeks' gestation. Karyotype was abnormal in 9 (82%) of 11 cases in which chromosomal analysis was successfully performed. Of these, 6 (67%) were 45,X.

CONCLUSIONS

The results suggested that embryonic/fetal pleural effusion in early pregnancy was associated with poor pregnancy outcome such as spontaneous abortion and chromosomal abnormality.

Prenatal course and pregnancy outcome of fetuses with a transient nuchal translucency

OBJECTIVES

This study was designed to correlate fetuses in a normal prenatal population who exhibited transient nuchal translucency (NT) with both prenatal course and pregnancy outcome.

METHODS

The fetuses with abnormal NT were followed by ultrasonography at 1-2-week intervals during their prenatal course. Fetuses with NT who exhibited no detectable congenital malformations were defined as the NTO group; fetuses with abnormal NT and structural malformations but no chromosomal abnormalities were placed in the SM group; and fetuses with abnormal NT, structural malformations, and chromosomal abnormalities were categorized as the CA group. The groups were compared by: maternal age, weeks of gestation by ultrasound and the NT value at the initial exam, the maximum NT value, and the duration of abnormal NT.

RESULTS

During the study period, 92 fetuses with abnormal NT were found, monochorionic twins excluded. Of the 92 fetuses, 80 were in the NTO group, 10 were in the SM group, and two were in the CA group. The maternal age and the gestational weeks at the initial diagnosis were not significantly different in the NTO and the SM groups. However, the NT value at the initial diagnosis, maximum NT value, and the duration of abnormal NT were significantly greater in the SM group than those values in the NTO group.

CONCLUSIONS

Fetuses with transient nuchal translucency commonly had structural malformations, particularly fetuses with significant and large persistent NT.

Early prenatal diagnosis of major cardiac anomalies in a high-risk population

OBJECTIVE

To examine the accuracy of early fetal echocardiography performed in a high-risk population combining transvaginal and transabdominal routes.

METHODS

A series of 330 high-risk pregnancies were screened by transvaginal and transabdominal scan at 12-17 weeks' gestation in a prospective multicentre trial in Spain between September 1999 and May 2001. A total of 334 fetal heart examinations were performed, including four twin pregnancies. Maternal age ranged from 17 to 46 years (mean 33 years with 36% of women over 34 years). The median gestational age at scan was 14.2 weeks (range 12-17 weeks). For each fetus, visualization of the four-chamber view, the origin of the great arteries, aortic and ductal arches and systemic venous return was attempted in a segmental approach. B-mode and colour/pulsed Doppler flow imaging were used in all cases. The duration of complete heart examination was less than 30 minutes. The examinations were performed by three experienced operators. Reliability was assessed by conventional transabdominal echocardiography at 20-22 weeks, by postnatal follow-up in the first three months of life, and/or by autopsy in cases of termination of pregnancy.

RESULTS

The rate of successful visualization of the fetal heart was 94.6% (316/334). In 48 out of 334 (14.4%) fetuses the final diagnosis was abnormal. In 38 out of 48 (79.2%) cases with heart defects the diagnosis was suspected at early echocardiography. In the group with congenital heart defects, 27 cases had an abnormal karyotype (56.3%) and 31 cases showed extracardiac anomalies (64.6%). There were 10 false-negative cases at early scan. There were no false-positive diagnoses.

CONCLUSIONS

This experience stresses the usefulness of early fetal echocardiography when performed by expert operators on fetuses specifically at risk for cardiac disease. The high rate of successful visualization of the fetal heart provides a reliable diagnosis of major cardiac defects at this early stage of pregnancy.