Medical Genetics - V. M. Zaporozhan 2005

Congenital Malformations
Genetic Counseling for Congenital Malformations

Congenital Malformations have a diverse Etiology. It is essential to keep in mind the Selection/32.html">Genetic heterogeneity of many malformations. For instance, Hydrocephalus can be monogenic (hydrocephalus resulting from aqueductal stenosis is inherited as an X-linked recessive trait), multifactorial, or the result of teratogenic factors. A malformation such as microcephaly may be inherited as an autosomal recessive trait, serve as a symptom of multiple congenital anomaly syndromes (e.g., Apert syndrome), occur in various Chromosomal Disorders (such as Down, Patau, and Edwards syndromes), or manifest as part of teratogenic syndromes (e.g., fetal alcohol syndrome, phenylpyruvic embryofetopathy, etc.).

Precise Diagnosis of hereditary pathology is of paramount importance for prognosticating offspring health. Genetic risk is calculated based on the type of inheritance. For example, neural tube closure defects (anencephaly, encephalocele, Spina bifida) are multifactorial malformations in the majority of cases. The recurrence risk for siblings and offspring is 4–5%. These defects may also be observed in Patau syndrome, Edwards syndrome, and polyploidy. In such cases, the genetic risk does not exceed 1%. An encephalocele can be a symptom of Meckel syndrome (encephalocele, polydactyly, Polycystic Kidney Disease), which is inherited in an autosomal recessive manner. If both parents are heterozygotes, the risk for siblings is 25%.

Methods of pharmacological Prevention have been developed for certain developmental malformations. Specifically, the administration of Folic acid during Pregnancy prevents the birth of children with neural tube defects.

Methods also exist for the preventative management of Hermaphroditism symptoms in the virilizing form of congenital adrenal hyperplasia in female infants. If prenatal diagnosis confirms this condition in the fetus, pregnant women are prescribed glucocorticoids. This Treatment prevents adrenal hyperplasia and excessive androgen synthesis. After birth, the child requires hormone replacement therapy.

Cases of intrauterine Surgical treatment for fetuses with lethal malformations are well documented. For example, diaphragmatic repair is feasible in cases of congenital diaphragmatic hernia (Fig. 9.23).

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Fig. 9.23. Fetal diaphragmatic repair for congenital diaphragmatic hernia: 1 — diaphragmatic repair; 2 — anterior abdominal wall repair