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Microcephaly may be diagnosed before birth by prenatal ultrasound, a diagnostic imaging technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.
In many cases, microcephaly may not be evident by ultrasound until the third trimester, and, therefore, may not be seen on ultrasounds performed earlier in pregnancy. The diagnosis of microcephaly may be made at birth or later in infancy. The baby's head circumference is much smaller than normal. During the physical examination, the physician obtains a complete prenatal and birth history of the child. In older babies and children, the physician may also ask if there is a family history of microcephaly or other medical problems. The physician will also ask about developmental milestones since microcephaly can be associated with other problems, such as mental retardation. Developmental delays may require further medical follow up for underlying problems.
A measurement of the circumference of the child's head is taken and compared to a scale that can identify normal and abnormal ranges.
Diagnostic tests that may be performed to confirm the diagnosis of microcephaly and identify abnormalities in the brain include:
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