Normal Fetal Study
    Use the interactive module below to familiarize yourself with echo images in the normal fetus.

    Landmarks to watch for are:
        » the spine
        » the transverse descending aorta
        » the interatrial septum
        » the left and right atrium
        » the interventricular septum
        » the right and left ventricle
        » the two atrioventricular valves

Indications for a Fetal Study
     Fetal studies should be restricted to those situations where certain indications are present, including:

Extracardiac Anomalies
    These defects may be seen in the presence of other anomalies and is quite variable depending on the other organs involved.  There is a 2% to 5% ^[1] incidence of cardiac defects when central nervous system malformations are present to as high as 50% when there are anomalies of the renal system.  Even when the lesser organ system is involved, the incidence of cardiac defects is still increased significantly enough over the incidence of the general population that fetal echocardiography is indicated.

    The echocardiographer should be aware of other such forms of extracardiac malformations that have a high occurance with specific forms of cardiac defects.  The most common is the omphalocele and either a VSD or tetralogy of Fallot.  The range of incidence may be from 10% if the caudal fold is involved to nearly 100% if the cephalic fold is involved ^[2]. .   The most common extracardiac association is from abnormal spleen formation and atrioventricular septal defects.  Asplenia is the absence of the spleen compared with polysplenia or multiple spleens that en masse make up a structure that is the approximate size of a normal spleen.  In asplenia, right isomerism (the morphologic similarity of paired structures that are normally dissimilar) may be present and abnormalities of the pulmonary flow and pulmonary venous drainage may be present with increased systemic venous anomalies.  In addition, there may be an increased incidence of arrhythmias from altered development of the sinoatrial node.

Abnormal Fetal Growth and Fetal Distress
     These features are not difficult to determine but may be related to abnormally poor fetal growth and fetal distress syndromes.  The fetus may have difficulty with the origins of the growth problems. Tachyarrhythmias can cause such problems but may not be present at the time of the examinations. Conditions such as hydrocephalus, micro- encephalopathy, holoprosencephaly, agenesis of the corpus callosum,  Meckle-Gruber syndrome, esophageal atresia, duodenal atresia,  diaphragmatic hernia, omphalocele, and renal dysplasia should be accompanied by a thorough evaluation for cardiac abnormailties.

Chromosomal Abnormalities
     When chromosomal abnormalities are detected by amniocentesis, fetal echocardiography should be indicated, because of the high association of congenital heart disease.  The most likely cardiac defect is dependent on the chromosomal abnormality present and the examiner must be aware of the defect most commonly seen with a given chromosomal abnormality. The most common chromosomal defect associated with atrioventricular septal defects is Trisomy 21, isolated ventricular septal defects, and Tetralogy of Fallot.

Fetal Cardiac Dysrrhythmias
     One of the most common reasons for referral of fetal echo is the presence of an irregular heart rhythm.  With few exceptions, most dysarrhythmias are not associated with defects in cardiac structure.  However, many defects can cause dysarrhythmias particularly when there is significant chamber dilatation.  Other considerations are in fetuses with l-transposition of the great arteries and congenital complete heart block.  These patients should be examined for this defect as well as for tricuspid valve abnormalities.

     Fetuses with supraventricular tachycardia will warrant close examination of the atrioventricular junction as there is are well known association of such arrhythmias with lesions such as Ebstein's anomaly of the tricuspid valve and L-transposition of the great arteries. (image Copyright 1995-2005 by Krzysztof P. Wroblewski )

Maternal Illnesses
     The association of specific maternal illnesses and the known teratogenic effect of certain drugs and chemical agents such as diabetes mellitus, connective tissue disorders, seizure disorders requiring chronic medication, and exposure to agents are known to produce anomalies. Maternal congenital heart disease, polyhydroamnios, diabetes mellitis, collagen-vascular disease, drug exposure ( alcohol, anticonvulsants, lithium, thalidomide and other teratogens), and pre-eclampsia are other conditions to consider performing fetal echocardiography.

    Hydrops fetalis, a condition where subcutaneous edema can cause fluid to collect in the body cavities, is assumed to be from an immune and non-immune origin. Rh differences in the mother and child (Rh negative mother and Rh positive child) may cause the mother's immune system to see the Rh positive blood cells of the baby as foreign bodies. The mother's immune system attacks the blood cells of the fetus and breaks them down. This results in anemia which can lead to fetal system failure and collection of fluids. In non-immune hydrops, the causes can be from diseases or complications that include anemias, congenital infections, liver disease, chromosomal abnormalities, or heart/lung defects. (image Copyright 1995-2005 by Krzysztof P. Wroblewski )

Prior Child with Heart Disease
     A common consideration in most centers for fetal echocardiography comes with a prior child with congenital defects.  While the incidence of a second-generation child with the same abnormality is low, parental concern of whether they should have a second child with possible illness is to be considered.

^{[1] [2] Echocardiography in Pediatric Heart Disease, Snider and Serwer}