A new Consult Series Statement by the Society for Maternal-Fetal Medicine (SMFM) published in the July issue of the American Journal of Obstetrics and Gynecology offers valuable clinical guidance on the diagnosis, evaluation, and management of mild fetal ventriculomegaly.
“Ventriculomegaly is a relatively common finding on prenatal ultrasound examination,” explains Duke maternal-fetal medicine specialist Jeffrey Kuller, MD, who serves as vice chair of the SMFM Publications Committee. "The SMFM published these new guidelines to help clinicians provide expert consultation for this condition.”
Some researchers divide prenatally detected ventriculomegaly into two categories: mild (10-15 mm-fetal lateral ventricle atrial diameter) or severe (>15 mm). However, because the risk for adverse outcome is higher when the prenatal lateral ventricles measure 13-15 mm versus 10-12 mm, the guidelines recommend using three categories: mild (10-12 mm), moderate (13-15 mm), or severe (>15 mm). To ensure accurate characterization, the document also provides guidance on the correct technique for measuring the lateral ventricle.
Mild ventriculomegaly may represent a normal variant, with more than 90 percent of cases resulting in a normal postnatal evaluation. However, 5 percent of mild to moderate ventriculomegaly cases result from congenital fetal infections, and another 5 percent result from abnormal karyotype. In addition, approximately 7-10 percent of fetuses with mild ventriculomegaly have other structural abnormalities at birth. The authors recommend further evaluation for all patients with mild to moderate ventriculomegaly to determine whether congenital infection or additional structural or genetic abnormalities are present when ventriculomegaly is detected:
- Testing for fetal structural anomalies. Detailed ultrasound (US) should be performed by an expert with experience in the diagnosis of fetal anomalies. When available, and particularly in the absence of such an expert, MRI is also recommended to detect anomalies not visible on US.
- Testing for genetic disorders. Amniocentesis with chromosomal microarray should be performed to detect fetal aneuploidy and copy number variants.
- Testing for congenital fetal infection. Women’s history should be reviewed for symptoms suggestive of cytomegalovirus (CMV) infection or exposure to toxoplasmosis or Zika virus. Regardless of history, women should be tested for CMV and toxoplasmosis. Polymerase chain reaction for CMV and toxoplasmosis can be included during amniocentesis. Testing for Zika virus should be performed according to the current guidelines.
The new guidelines advise clinicians to perform follow-up US to assess whether the ventriculomegaly has progressed; when ventriculomegaly is progressive, certain surgical interventions may be necessary. To that end, women should also receive counseling from a clinician with expertise in the prenatal diagnosis and prognosis of fetal ventriculomegaly.
After complete evaluation to rule out structural anomalies, genetic disorders, and congenital fetal infection, several recommendations can be made regarding counseling women on prognosis:
- Isolated mild ventriculomegaly: Given the high likelihood of a normal neurodevelopmental outcome (>90 percent), these women should be counseled that the outcome is favorable and that the infant is likely to be normal.
- Isolated moderate ventriculomegaly: These women should be counseled that the outcome is likely to be favorable, but the fetus has an increased risk of neurodevelopmental disabilities.
Finally, the timing and mode of delivery should not be modified in the setting of mild or moderate ventriculomegaly but rather follow standard obstetric indications.