Body-stalk anomaly is a severe abdominal wall defect that results from abnormalities in the development of the cephalic, caudal, and lateral embryonic body folds. This maldevelopment results in the absence or shortening of the umbilical cord with the abdominal organs lying outside the abdominal cavity and directly attached to the placenta (Shalev et al., 1995; Smrcek et al., 2003). Body-stalk anomaly was first described by Kermauner in 1906 in a newborn with an abdominal wall defect consisting of an amniotic sac that contained viscera; the anterior wall of the sac was directly attached to the placenta and there was no umbilical cord. Other than the references given in textbooks of pathology, body-stalk anomaly was not appreciated in the general obstetric literature until the report of Lockwood et al. in 1986.

After gastrulation, the embryo consists of a three-layered, flat, oval germinal disk. The rapid growth of the embryo, especially along the sagittal axis causes the germinal disk to curve. Through circumferential folding, the embryo becomes cylindrical. As a result of this process, the body of the embryo closes, the body stalk forms, and an intraembryonic coelom (peritoneal cavity) separates from an extraembryonic coelom (chorionic cavity) (Giacoia, 1992). The amniotic cavity, which is initially located dorsal to the germinal disk, grows rapidly and eventually encircles the fetus, obliterates the chorionic cavity, and envelops the umbilical cord. The abnormality in the folding process prevents this obliteration of the chorionic cavity and formation of the umbilical cord. Without an umbilical cord, the fetus becomes directly attached to the placental chorionic plate. This body-stalk anomaly consists of a sac of amnion–mesoderm that contains the displaced abdominal organs (Giacoia, 1992).

Causes proposed for body-stalk defect include early amnion rupture with direct mechanical pressure and amniotic bands (see Chapter 99), vascular disruption of the early embryo, or an abnormality in the germinal disk that leads to the formation of an anomalous amniotic cavity (Van Allen et al., 1987). In the early amnion-rupture theory, the abdominal wall and spinal defects could be secondary to the passage of the lower half of the fetal body into the coelomic cavity through the defect in the amniotic sac. The fetus has no room to move and remains practically attached to the placenta. Limb amputations and encephalocele could be secondary to the entrapment of the fetal skull and/or limbs in the coelomic cavity (Daskalakis et al., 1997). Alternatively, early generalized compromise of embryonic blood flow could lead to a failure of closure of the ventral body wall and persistence of the coelomic cavity (Van Allen et al., 1987). This could also lead to a rupture of an unsupported amnion and formation of amniotic bands.

Body-stalk anomaly is the rarest and most severe of the abdominal wall defects. The incidence of body-stalk anomaly in a population of Scottish patients identified by abnormal maternal serum screening results was 1 in 14,273 (Mann et al., 1984). The incidence of body-stalk anomaly in a Hawaiian birth defects registry that encompassed the years 1986 to 1997 was 0.32 per 10,000 births (Forrester and Merz, 1999). Recently, an increased incidence of body-stalk anomaly was noted in a population of first trimester fetuses studied for nuchal translucency thickness. In this first trimester population, the incidence of body-stalk anomaly was between 10 in 4116 cases and 14 in 106,727 cases or 1 in 7500 fetuses (Daskalakis et al., 1997; Souka et al., 1998). Another series of 11 cases of Limb–body wall complex suggested an incidence of 1 in 3000 (Luehr et al., 2002). Several case reports exist of body-stalk anomaly and Limb–body wall complex in association with monozygotic twinning, triplet pregnancy, and with maternal cocaine abuse (Viscarello et al., 1992; Martinez et al., 1994; Smrcek et al., 2003).

The criteria for the diagnosis of body-stalk anomaly in the first trimester include demonstration of abdominal organs in the extraembryonic coelom and a short umbilical cord with only two vessels (Ginsberg et al., 1997). The diagnosis may be more difficult to make during the second trimester than during the first because of the presence of severe oligohydramnios. During the second trimester, Goldstein et al. (1989) suggested that body-stalk anomaly should be strongly considered when there is a body wall defect, skeletal abnormalities, and the umbilical cord is absent or very rudimentary (Figures 60-1 and 60-2).

In a multicenter project of screening for chromosomal defects by fetal nuchal translucency thickness and maternal age, 14 of 106,727 fetuses examined had a body-stalk anomaly (Daskalakis et al., 1997). During the first trimester, the ultrasonographic features observed included a major abdominal wall defect, severe kyphoscoliosis, and short umbilical cord. In all of the cases observed, the upper part of the fetal body was in the amniotic cavity and the lower part was in the coelomic cavity. The nuchal translucency thickness was above the 95th percentile in 10 of the 14 cases, but the fetal karyotype was normal in 12 of the 14 fetuses evaluated. These authors suggested that early amnion rupture before obliteration of the coelomic cavity is a possible cause of the syndrome (Daskalakis et al., 1997).

Multiple case reports have described the prenatal sonographic diagnosis of body-stalk anomaly (Lockwood et al., 1986; Jauniaux et al., 1990; Giacoia, 1992; Shalev et al., 1995; Takeuchi et al., 1995; Ginsberg et al., 1997). An additional helpful sonographic finding is the presence of scoliosis, which is observed in approximately 75% of cases (Ginsberg et al., 1997) (Figures 60-3 and 60-4). Scoliosis is thought to be due to the absence of thoracolumbar and paraspinal muscles on the ipsilateral side of the abdominal wall defect. In addition, it is thought that fetal hyperextension and direct attachment to the placenta, which limit fetal movement, result in skeletal anomalies.