Comparison of Fetal Cerebellum and Cisterna Magna Length by 2D and 3D Ultrasonography between 18 and 24 Weeks of Pregnancy

Are fetal gender and gestational age related to the size of cisterna magna?

OBJECTIVES

The purpose of this article was to explore whether the gestational age(GA)and gender could affect the size of the cisterna magna (CM).

METHODS

This study that included pregnant women who were between 20 ∼ 39⁺⁶. The recorded included BPD, HC, anteroposterior diameter of CM and gender. The fetuses were divided into normal and isolated enlargement of the CM (IECM)group for statistical analysis.

RESULTS

Seven hundred ninety six fetuses with normal CM, 412 cases were boys and 384 cases were girls. 73 fetuses with IECM, 59 cases were boys and 14 cases were girls. The anteroposterior diameter of the CM increased with GA during 20-26⁺⁶weeks. After 27 weeks, the anteroposterior diameter of CM became stable. In the IECM group, the mean anteroposterior of male and female fetuses were 1.31 ± 0.18 cm and 1.24 ± 0.15 cm, respectively. The IECM fetus accounted for 8.4% of the total number of fetuses, male IECM accounted for 14.3% of normal male fetus, and female fetus was 3.6%, which showed that male fetus had a higher rate of IECM than female (χ2 = 21.6, p<.001).

CONCLUSIONS

There is a gender difference between normal fetuses and IECM fetuses. Based on our finding, it is reasonable to establish the normal value of CM according to the gender difference.

Reference range of fetal transverse cerebellar diameter between 18 and 24 weeks of pregnancy in a Brazilian population

To determine a reference range of fetal transverse cerebellar diameter in Brazilian population. This was a retrospective cross-sectional study with 3772 normal singleton pregnancies between 18 and 24 weeks of pregnancy. The transverse cerebellar diameter was measured on the axial plane of the fetal head at the level of the lateral ventricles, including the thalamus, cavum septum pellucidum, and third ventricle. To assess the correlation between transverse cerebellar diameter and gestational age, polynomial equations were calculated, with adjustments by the determination coefficient (R2). The mean of fetal transverse cerebellar diameter ranged from 18.49 ± 1.24 mm at 18 weeks to 25.86 ± 1.66 mm at 24 weeks of pregnancy. We observed a good correlation between transverse cerebellar diameter and gestational age, which was best represented by a linear equation: transverse cerebellar diameter: -6.21 + 1.307*gestational age (R2 = 0.707). We determined a reference range of fetal transverse cerebellar diameter for the second trimester of pregnancy in Brazilian population.

Normative data for fetal cisterna magna length measurement between 18 and 24 weeks of pregnancy

PURPOSE

The aim of this study was to determine normative data for fetal cisterna magna length (CML) measurement in a Brazilian population.

METHODS

This was a retrospective cross-sectional study on 3,862 normal singleton pregnancies between the 18th and 24th weeks of pregnancy. Fetal CML was measured in the axial plane of the fetal head, at lateral ventricle level, including the cavum septum pellucidum, thalamus, third ventricle, and transverse cerebellar diameter. The anteroposterior measurement was made between the posterior border of the cerebellar vermis and the internal face of the occipital bone. To assess the correlation between CML and gestational age (GA), polynomial equations were calculated, with adjustments using determination coefficient (R2).

RESULTS

The mean CML ranged from 4.29±0.93 mm at 18 to 18+6 weeks to 5.58±1.23 mm at 24 to 24+6 weeks of pregnancy. There was a good correlation between CML and GA, best represented by a linear equation: CML=0.535+0.208*GA (R2=0.084).

CONCLUSION

We established normative data for fetal CML in the second trimester of pregnancy, in a large Brazilian population.