Читать книгу Protocols for High-Risk Pregnancies - Группа авторов - Страница 51

Sonographic detection of major malformations

Оглавление

The genetic sonogram is a term that has been used to describe second‐trimester sonographic assessment of the fetus for signs of aneuploidy. The detection of certain major structural malformations that are known to be associated with aneuploidy should prompt an offer of genetic amniocentesis. Table 5.2 summarizes the major structural malformations that are associated with the most common trisomies. Given the increasing popularity of first‐trimester screening, many advanced obstetric ultrasound practitioners have attempted to bring the genetic sonogram forward in gestation so that an anomaly scan may also be performed toward the end of the first trimester. Relatively limited data are available to validate the accuracy of the genetic sonogram in the first trimester for general population screening, and therefore the optimal time remains at about 18–22 weeks of gestation.

Table 5.2 Sonographic findings associated with trisomies 21, 18, and 13

Trisomy 21 Trisomy 18 Trisomy 13
Major structural malformations
Cardiac defects: Cardiac defects: Holoprosencephaly
• Atrioventricular (AV) canal defect • Double outlet right ventricle Orofacial clefting
• Ventricular septal defect • Ventricular septal defect Cyclopia
• Tetralogy of Fallot • AV canal defect Proboscis
Duodenal atresia Meningomyelocele Omphalocele
Cystic hygroma Agenesis of the corpus callosum Cardiac defects:
Hydrops fetalis Omphalocele • Ventricular septal defect
Diaphragmatic hernia • Hypoplastic left heart
Esophageal atresia Clubbed or rocker‐bottom feet Renal abnormalities Orofacial clefting Cystic hygroma Hydrops fetalis Polydactyly Clubbed or rocker‐bottom feet Echogenic kidneys Cystic hygroma Hydrops fetalis
Minor sonographic markers
Nuchal thickening Nuchal thickening Nuchal thickening
Mild ventriculomegaly Mild ventriculomegaly Mild ventriculomegaly
Short humerus or femur Short humerus or femur Echogenic bowel
Echogenic bowel Echogenic bowel Enlarged cisterna magna
Renal pyelectasis Enlarged cisterna magna Echogenic intracardiac focus
Echogenic intracardiac focus Choroid plexus cysts Single umbilical artery
Hypoplastic nasal bones Micrognathia Overlapping fingers
Brachycephaly Strawberry‐shaped head Growth restriction
Clinodactyly Clenched or overlapping fingers
Sandal gap toe Single umbilical artery
Widened iliac angle Growth restriction
Growth restriction

When a major structural malformation is found, such as an atrioventricular canal defect or a double‐bubble suggestive of duodenal atresia, the risk of trisomy 21 in that pregnancy is increased by approximately 20–30‐fold. For many patients, such an increase in their background risk for aneuploidy will be sufficiently high to justify genetic amniocentesis.

Protocols for High-Risk Pregnancies

Подняться наверх