The effect of trisomy 18 on transverse cerebellar diameter

Article Abstract:

Trisomy 18 is a congenital abnormality in which the fetus has three variants of chromosome 18 instead of the normal two. Fetuses with this abnormality have a variety of malformations that vary by case. Abnormalities such as a small cerebellum (part of the brain) have been reported in some infants born with trisomy 18. Cerebellar diameter was measured in fetuses during the second and third trimesters of pregnancy to determine if it was smaller than normal when trisomy 18 was present. Ultrasonography, a diagnostic imaging technique that uses high frequency sound waves, was used to examine and measure cerebellar diameter in 19 fetuses with trisomy 18. When measurements were adjusted for gestational age by using the last menstrual period, 11 of 19 (57.9 percent) of the measured cerebellar diameters were significantly below normal. If fetal biometry (a method of estimating fetal age by comparison of a number of physical measurements against a standard) was used to judge gestational age, only four measurements were below normal to the same extent. Small cerebellar size occurred more often in the fetuses measured in the third trimester (9 of 12) than those measured in the second trimester (2 of 7). Small cerebellar diameter was more likely to occur in fetuses who also suffered intrauterine growth retardation or central nervous system abnormalities. Although small cerebellar size does appear more likely to occur in fetuses with trisomy 18, it is not consistently present such that it could be used to diagnose trisomy 18. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Measurement, Chromosome abnormalities, Cerebellum

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Transvaginal ultrasonographic definition of the central nervous system in the first and early second trimesters

Article Abstract:

The results from ultrasonographic evaluation of central nervous system (CNS) anatomy in fetuses between the ages of 6 and 14 weeks are presented. High-frequency transvaginal ultrasonography, a noninvasive method in which a probe is inserted into the vagina and used to project an image of the fetus onto a screen, was used to examine the fetuses of 133 women with low-risk pregnancies. The gestational ages of the fetuses were computed, and the CNS structures that could be visualized at each age are described. More structures could be detected in older fetuses. Some of the resulting images are presented. As more and more clinicians use transvaginal ultrasonography, it will become increasingly important for them to understand the appearance of the normal fetal CNS if they are to accurately diagnose abnormalities in the first and second trimesters of pregnancy. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Usage, Diagnosis, Birth defects, Prenatal diagnosis, Fetal nerve tissue, Prenatal ultrasonography, Ultrasonics in obstetrics

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