Fetal Echocardiography

Fetal echocardiography

Since the first report of fetal echocardiography in 1972 by Winsberg, several advances in ultrasound technology have occurred allowing detailed evaluation of cardiac anatomy in the second trimester fetus. Fetal echo is indicated in high risk pregnancies where the chances of fetus having a congenital heart disease (CHD) are likely to be high e.g., in fetus with extracardiac anomalies picked up on obstetric ultrasound, those with a history of CHD in family, maternal diabetes (especially insulin dependent), maternal connective tissue disorder etc. The reported sensitivity of fetal echo has ranged from 4-96% in various series depending upon the equipment, level of training, study design and examination technique. Although many CHD can be detected in four chamber view, an important group malformations that would need early intervention are likely to be missed. Hence a detailed echocardiographic examination including the outflow views must be done. Defects like atrial septal defect and patent ductus arteriosus cannot be diagnosed in fetal echo, as these are part of normal fetal physiology. Other CHD like coarctation of aorta, small ventricular septal defects, mild valvular stenosis, partial anomalous pulmonary venous drainage are also difficult to diagnose. Ultrasound assessment of fetus, however, has a clear role in the diagnosis, monitoring and management of fetuses with sustained arrhythmias. Prenatal diagnosis of CHD helps in planning the optimal management of the baby e.g. a fetus with a ductus dependent lesion can be planned to be delivered in a tertially care centre for stabilisation and early initiation of prostaglandin therapy to avoid acidosis and organ damage. Future of fetal medicine lies in fetal cardiac surgery for which echocardiography will play a very important role.

Evaluation of prenatal diagnosis of congenital heart disease

Prenatal diagnosis performed by fetal ultrasound scan is now a routine part of antenatal care in many countries. That an increasing number of fetal anomalies may be detected on prenatal ultrasound is beyond doubt. What is possible is not, however, always practical, especially when congenital heart diseases (CHDs) are concerned and when whole antenatal populations are screened rather than high-risk groups. Thanks to our registry of congenital anomalies, a retrospective study was undertaken to evaluate the prenatal detection of CHDs by ultrasound scan in 131,760 consecutive pregnancies of known outcome from 1979 to 1988. Only 84 out of 912 malformed fetuses with CHDs without chromosomal anomalies were detected (9.2 per cent). The sensitivity of detection varied from around 38 per cent for malformations such as hypoplastic left heart and single ventricle to around 5 per cent for ventricular and atrial septal defects. The effectiveness of the detection of some forms of major congenital heart disease has increased dramatically since 1987 by including routine examination of the four-chamber view and of the inflow and outflow tracts of the fetal heart. Our results stress the need to obtain a definite clear four-chamber view, to perform scans at > or = 18 weeks of gestation, and to train sonographers in order to improve the prenatal detection of CHDs.

Outcome of prenatally detected cardiac malformations

Reliable, prenatal detection of congenital heart disease has become possible over the past decade with the evolution of fetal echocardiography. We have documented the outcome of 170 cardiac defects diagnosed prenatally since 1984. Of 170 cases, 55 (32%) had major extracardiac malformations and 45 (28%) chromosomal abnormalities (16 had both). Elective termination was chosen in 77 (45%) pregnancies. Of 93 continuing pregnancies 15 were stillborn and 43 died postnatally (48% of these fetuses and infants had extracardiac or chromosomal anomalies, or both). Thirty-five patients survive at 1 to 80 months (mean 36). Aneuploidy or extracardiac defects are present in 20% of survivors. Nonimmune hydrops secondary to cardiac failure was present in 7 continuing pregnancies and none of these patients survived. The prognosis of prenatally diagnosed cardiac lesions is negatively influenced by the presence of cardiac failure, aneuploidy or extracardiac malformations, or a combination of these. Optimal counseling and management requires the identification of these conditions when present.

Comparative audit of booking and mid-trimester ultrasound scans in the prenatal diagnosis of congenital anomalies

During 1988 and 1989, 3565 women booked under consultants who performed an ultrasound scan at booking, whilst 4984 booked under consultants who performed a formal mid-trimester scan between 16 and 18 weeks. All significant anomalies diagnosed prenatally and in the neonatal period were recorded, the incidence in each group being 12.9/1000 and 9.83/1000, respectively (NS). The sensitivity of diagnosis before 20 weeks was 45 percent in the 'mid-trimester' group (kappa 0.62) compared with 30 percent in the 'booking' group (kappa 0.46), overall sensitivity of prenatal diagnosis, however, being similar in both groups (63 vs. 65 percent, kappa 0.77 vs. 0.79). Cardiac anomalies were the single largest group which were not detected equally prenatally in both groups. This study shows that formal mid-trimester scanning leads to anomalies being detected significantly earlier in the antenatal period. Although not statistically significant, three lethal anomalies were missed prenatally in the 'booking' group which we would have expected to diagnose on a mid-trimester scan. These figures are discussed in the light of previous reports.