Early sonographic diagnosis of fetal midline disruption syndromes

[Amniotic band syndrome: prenatal diagnosis and management challenges (about 2 cases of lethal malformations)]

Amniotic band syndrome (ABS) comprises of a spectrum of complex congenital malformations mainly interesting the limbs, but even the craniofacial region and the thoracoabdominal axis. There are two major opposing pathophysiological theories: premature rupture of the amniotic sac (exogenous growth theory) would result in the formation of fibrous bands which would lead to strangulation, thus causing the observed abnormalities; the endogenous theory holds that this is a syndrome of vascular origin and that the bands have no causative role. Prognosis depends on the severity of malformations. We here report two cases of lethal malformations in order to discuss the challenges in the diagnosis and treatment of amniotic band syndrome. This study mainly aims to highlight the role of prenatal diagnosis in the therapeutic management of this embryo-fetopathy.

Role of Ultrasound in Body Stalk Anomaly and Amniotic Band Syndrome

Body stalk anomaly (BSA) and amniotic band syndrome (ABS) are rare similar fetal sporadic polymalformative syndromes of unknown etiology, though there are certain differences between them. BSA is a combination of developmental abnormalities involving neural tube, body wall, and the limbs with persistent extra embryonic coelomic cavity. ABS is characterized by the presence of thin membrane-like strands attached to fetal body parts and causing constrictions and amputations. This is a cohort study involving 32,100 patients who were referred for routine antenatal ultrasound scan. The data was entered prospectively into a computer database. The duration of study was 3 years. In our study, ultrasound examination in 86 patients demonstrated ventral wall defects, craniofacial defects, and spinal and limb deformities as isolated or combined abnormalities. In those, 10 patients were suspected/diagnosed as BSA/ABS including a twin of a dichorionic diamniotic gestation. The typical features of body stalk anomaly can be detected by ultrasound by the end of the first trimester, which is important for the patient counselling and management. We are presenting these rare conditions and highlighting the importance of early sonographic imaging in diagnosing and differentiating them from other anterior abdominal wall defects.

Performing a fetal anatomy scan at the time of first-trimester screening

Over the past decade, prenatal diagnosis has shifted rapidly from the second trimester into the first trimester. Although the nuchal-translucency scan may detect a small proportion of fetal structural malformations, fetal anatomy is not routinely assessed until the fetal anatomical survey is performed in the second trimester between 18 and 22 weeks. The recent development of high-frequency transvaginal ultrasound transducers has led to vastly improved ultrasound resolution and improved visualization of fetal anatomy earlier in gestation. Several pilot studies of a first-trimester anatomic survey have reported detection rates comparable with those achieved in the routine second-trimester anatomic survey. As advanced ultrasound technology becomes more available, there is an urgent need to evaluate the diagnostic ability of a first-trimester anatomic survey and to determine the role of a first-trimester anatomic survey in the current screening paradigm.

Prenatal diagnosis of musculoskeletal anomalies

Musculoskeletal anomalies are not uncommon in prenatal life. They can be either sporadic or part of chromosomal syndromes causing prenatal morbidity and mortality. The prenatal diagnosis of musculoskeletal anomalies is based on information assembled from various imaging modalities and from biochemical and genetic workups. The prenatal diagnosis can serve as a prognostic tool and in counseling the parents. Among the imaging methods, ultrasonography is the most popular and cost effective in observing and following fetal development from the very early stages of gestation. Transvaginal sonography can detect and identify most of the normal and the specific pathologic changes very close to the stage of their embryogenic development. From a practical point of view, early detailed transvaginal sonography screening at 14 to 15 weeks of gestation is very useful while late detection at 20 to 23 weeks of gestation may provide some additional information in low-risk pregnancies. Very early screening, even during the ninth week, may be indicated in high-risk pregnancies. Additional genetic counseling is recommended when abnormal findings are suspected. We summarize the diagnostic approach and the information available for the most common musculoskeletal anomalies.

Prenatal ultrasound diagnosis and management of body stalk anomaly: analysis of nine singleton and two multiple pregnancies

OBJECTIVE

To determine prenatal ultrasonographic features and management of fetuses with body stalk syndrome in singleton and multiple gestations.

METHODS

In a retrospective chart analysis we reviewed all cases with body stalk anomaly diagnosed in our prenatal unit between 1994 and 2001. During this time period we adopted a uniform approach to the investigation of cases of body stalk anomaly, including amniocentesis or chorionic villus sampling (CVS) for fetal karyotyping. A general schematic sonographic examination was performed to search for fetal abnormalities and was followed by detailed two-dimensional and color-coded Doppler echocardiography. Nuchal translucency (NT) measurements were performed before 14 weeks of gestation. Postmortem examinations of fetuses were performed following termination by induction with prostaglandin.

RESULTS

Eleven fetuses with body stalk anomaly were diagnosed, including two multiple pregnancies complicated by discordant body stalk anomaly. The typical ultrasonographic features were a major abdominal wall defect, severe kyphoscoliosis, limb abnormalities, neural tube defects, and a malformed, short umbilical cord with a single artery. None of the fetuses demonstrated craniofacial defects. All placentae that were examined showed evidence of persistence of the extra-embryonic celomic cavity. NT measurements were abnormal in all cases. Fetal karyotyping was normal in ten cases. In one case CVS showed a mosaic trisomy 2 (46,XX/47,XX,+ 2). Selective fetocide was performed in one trichorionic-triamniotic triplet pregnancy in early gestation, which was followed by normal development of the remaining healthy dichorionic-diamniotic twins. In a monochorionic-diamniotic twin pregnancy with one affected fetus ultrasound surveillance showed the normal development of the unaffected twin.

CONCLUSIONS

We present a large series of body stalk anomaly, including multiple gestations, with thoraco- and/or abdominoplacental attachment and without craniofacial defects. This specific phenotype may be explained by embryonic maldevelopment. The typical features of body stalk anomaly can be detected by ultrasound by the end of the first trimester, which is important for patient management. Consequently, this anomaly should be distinguished from other fetal abdominal wall defects.

First trimester malformation screening

First trimester fetal malformation screening still represents a diagnostic challenge in modem obstetrics. Being solely dependent on ultrasound instrumentation, and the skill and experience of the operator, recently improved by introducing high frequency transvaginal approach and digital image processing. This opens a new field of ultrasound in obstetrics called sonoembriology. Until now sonoembriology in routine clinical practice resulted in numerous reports about early detection of rare anomalies and uncommon syndromes. The reported sensitivity of sonoembriology with a respect to a final pregnancy outcome was more than 60% of all malformations in total, while in combination with ultrasound screening in second trimester, increases to in excess of 80%. The commonest anomalies detected by sonoembriology are anomalies of the head and brain, heart, abdominal wall, unbilical cord, urinary tract and skeleton. There is an important role of sonoembriology in the assessment of the nuchal translucency in the screening programme for chromosomal anomalies. This changes the well-known concept "fetus as a patient" to "embryo as a patient" and opens new frontiers in fetal diagnosis and therapy.