Normal intracranial BS/BSOB ratio values in the first trimester of single gestations with live fetuses in a Korean population

Sung Hee Yang, Hyun Sook An, Jin Soo Lee, Changsoo Kim


Aim: The purpose of this study was to determine the normal length of the brainstem (BS) in Korean fetuses and to evaluatethe usefulness of the routine measurement of BS size in the first trimester of pregnancy for the early detection of spina bifida.

Material and methods: A total of 2,621 normal singleton pregnant Korean women at 10+6 to 13+6 weeks of gestation were selected for this retrospective cross-sectional study. Ultrasonography was used to measure the length of the longest vertical depth diameter of the BS and brainstem-occipital bone (BSOB) in order to obtain the BS to BSOB ratio.

Results: The best indicators for spina bifida ranged from 1.00±0.24 mm to 4.70±0.46 mm for the BS and from 2.90±0.36 mm to 8.50±0.92 mm for the BSOB. For the gestational period, BS (R=0.70) and BSOB (R=0.81) values were considered statistically significant (p<.0001). The value of the BS to BSOB ratio was <1.0 in normal fetuses, and was not correlated with the gestational age.

Conclusion: Measurement of BS and BSOB diameter in the first trimester is thought to provide the best reference marker for evaluating the posterior brain for diagnosis of spina bifida.


gestational age; spina bifida; brainstem; posterior brain

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