The cisterna magna size in normal second-trimester fetuses.

OBJECTIVE

The purpose of this study was to evaluate cisterna magna size of the fetuses between 16 and 24 weeks of gestation, and to establish a normogram for cisterna magna measurements during gestation.

METHODS

A prospective study of normal singleton pregnancies was established. Measurement of the fetal cisterna magna was performed by transabdominal ultrasonography between 16 and 24 weeks of gestation in 194 fetuses.

RESULTS

A linear correlation was obtained between gestational age (GA) and cisterna magna (R(2)=0.75, P<0.0001). A linear correlation was also found between biparietal diameter and cisterna magna (R(2)=0.74, P<0.0001). The normal mean (+/-SD) for each gestational week was defined.

CONCLUSION

The present data offer the normal range of the cisterna magna. Cisterna magna measurement may provide normative data for fetal growth and development. Abnormal measurement of cisterna magna may be a clue for posterior fossa pathologies or a chromosomal disorder.