**3.4. Anencephaly**

was isolated in only 24% of the fetuses, and isolated callosal abnormalities are associated with

• Genetic assessment. Genetic factors are most common. Among the genetic causes, "syndromic" diagnosis is made in 30–45% of cases and a monogenic cause can be identified in 20–35%. Over 200 genetic syndromes, many of which may have variable phenotype,

• Magnetic resonance imaging (MRI) is most helpful after the 20th week of gestation, since about 20% of apparently isolated cases diagnosed by ultrasound have associated CNS

• Evaluation of fetal well-being. If an isolated agenesis of corpus callosum is detected and the chromosomes are normal, the usual standard pregnancy management should be

Vaginal delivery is recommended unless is significant hydrocephalus with macrocephaly.

'Isolated' Dandy-Walker malformation (DWM) in the light of recent literature, which has demonstrated a potential good clinical and intellectual outcome of fetuses presenting with DWM characterized by partial vermian agenesis and absence of associated anatomical anom-

• Assessment for associated CNS and extra-CNS anomalies. The presence of the additional anomalies adversely affects survival and prognosis for the infant and child with DWM. The risk of associated intracranial anomalies appears to be 20–60%, and in this situation, the

• Genetic assessment. In the syndromic form of DWM, malformations of the heart, face, limbs, or gastrointestinal or genitourinary system may be present. DWM may occur as part of a Mendelian disorder (e.g., Meckel syndrome), a chromosomal aneuploidy (e.g., 45X, triploidy), environmental exposures (e.g., rubella, alcohol), a multifactorial etiology (e.g., congenital heart defect, neural tube defects), or as a sporadic defect (e.g., holoprosencephaly). • Evaluation of fetal well-being. The option for elective termination of pregnancy is offered for parents if the diagnosis of DWM with associated CNS anomalies is made early. If the diagnosis is made in the third trimester, conservative management is recommended. In

mental retardation and perinatal mortality are increased [16].

normal neurodevelopmental outcome in approximately two-thirds of fetuses [17].

include disorder of the corpus callosum as a feature.

*3.2.1. Pregnancy management*

474 Congenital Anomalies - From the Embryo to the Neonate

anomalies on MRI [18].

recommended.

alies [19].

*3.2.2. Delivery management*

Delivery prior to term is not advisable [16].

**3.3. Dandy-Walker malformation**

*3.3.1. Pregnancy management*
