Hydrops fetalis: Increased fluid retention in serous cavities and placenta can be caused by cardiac insufficiency, metabolic disorder, infec-tion-induced or congenital fetal anemia, rhesus immunization, and chromosomal abnormalities.

In monochorionic twins, the hydrops of one twin is caused by fetofetal transfusion through arteriovenous shunts.

In addition to showing an ascites (68) (Fig. 69.3), sonography can visualize pleural and pericardial effusions (79) (Fig. 69.4) and possibly a generalized cutaneous edema.

Risk for fetal trisomies 100T [ % ] (Ref': Pandya et al>

20 22 24 26 28 30 32 34 36 38 Maternal age [ years ]

The cardiovascular system is the first functioning organ system of the fetus. As from the 6th gestational week, fetal heart motion can be seen. Absent fetal heartbeats and growth retardation, usually accompanied by an indistinctly outlined fetus, indicate fetal demise and generally require dilatation and curettage. Because of their high sound energies, Doppler and color Doppler sonography should be used selectively, for instance, in cases of suspected growth retardation or cardiac malformation (refer to p. 63).

First, the position of the heart has to be determined: it should be one third to the right and two-thirds to the left of a straight line drawn from the spine to the anterior thoracic wall on the transverse section. The sagittal section must be oriented to visualize the aortic arch (15) and its brachiocephalic branches (82,117,123) (Fig. 70.1). In addition to the cardiac valves, the four-chamber view should identify both atria (116) and both ventricles (115) (Fig. 70.2) and exclude any ventricular septum defect (VSD) or atrial septum defect (ASD). By tilting the probe slightly from this plane, the inflow of blood into the left ventricle through the mitral valve (118) as well as the outflow through the aortic valve (119) can be visualized in this so-called five-chamber view (Fig. 70.3). Moreover, a VSD in the membranous portion of the septum is better delineated in this plane.

Heart and Vessels:

A small ASD or VSD as well as cardiac anomalies with right-to-left shunts can be definitively excluded only by color-coded echocardiography performed by an experienced examiner. Transposition of the great arteries

(TGA) might not be apparent on the four-chamber view and it is therefore necessary to look for crossed outflow tracts and aortic and pulmonic valves on the short axis view.

The evaluation of the GI tract must, among other findings, exclude a "double bubble" sign, which would suggest a duodenal atresia or stenosis. The anechoic "bubbles" correspond to the stomach and to the duodenum proximal to the stenosis, respectively, both filled with fluid. This finding should be confirmed in a second plane, to avoid a false positive diagnosis due to double sectioning of the stomach in a tangential plane. It should be kept in mind that a hernia of the anterior abdominal wall (120) (Fig. 71.1) next to the umbilical vessels (96) is physiologic until the 11th gestational week and should not be mistaken for a true omphalocele.

After the 15th gestational week, renal malformations are often indirectly revealed by a decreased amount of amniotic fluid (oligohydramnios) or its absence (anhydramnios) or by an empty urinary bladder because the amount of amniotic fluid corresponds to the renal excretion of urine at this time.

Fig. 71.1b

The normal renal parenchyma (29) already shows the less echogenic pyramids (30) separate from the anechoic collecting system (31) on the longitudinal section (Fig. 71.2). A summary of the intrauterine growth of the kidney is found in Figure 71.2 c.

Fig. 71.2b

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