Asymmetric cortical development and prognosis in fetuses with isolated mild fetal ventriculomegaly: an observational prospective study.

Background: Assessments of cortical development and identifying factors that may result in a poor prognosis for fetuses with isolated mild ventriculomegaly (IMVM) is a hot research topic. We aimed to perform a constant, detailed assessment of cortical development in IMVM fetuses using ultrasound and determine whether asymmetric cortical development occurred. Moreover, we aimed to estimate the prognosis of IMVM fetuses and compare the difference in the prognosis of IMVM fetuses presenting symmetric and asymmetric cortical maturation.

Methods: IMVM was diagnosed by regular ultrasound, neurosonography and fetal MRI. Genetic and TORCH examinations were conducted to exclude common genetic abnormalities and TORCH infection of fetuses. Ultrasound examinations were conducted at an interval of 2-3 weeks to record sulcus development in IMVM fetuses using a scoring system. The neonatal behavioral neurological assessment (NBNA), the Ages and Stages Questionnaire, Third Edition (ASQ-3) and the Bayley Scales of Infant Development, First Edition (BSID-I) were performed after birth.

Results: Forty fetuses with IMVM were included: twenty showed asymmetric cortical maturation and twenty showed symmetric cortical maturation. For IMVM fetuses presenting asymmetric cortical maturation, the mean gestational age (GA) at the first diagnosis of relatively delayed development was 24.23 weeks for the parieto-occipital sulcus, 24.71 weeks for the calcarine sulcus, and 26.43 weeks for the cingulate sulcus. All the sulci with delayed development underwent 'catch-up growth' and developed to the same grade as the sulci of the other hemisphere. The mean GA at which the two sides developed to the same grade was 29.40 weeks for the parieto-occipital sulcus, 29.30 weeks for the calcarine sulcus and 31.27 weeks for the cingulate sulcus. The NBNA, ASQ-3 and BSID-I scores of all patients were in the normal range.

Conclusions: IMVM fetuses may show mild asymmetric cortical maturation in the second trimester, but the relatively delayed sulci undergo 'catch-up growth'. The neurodevelopment of IMVM fetuses presenting asymmetric cortical maturation and 'catch-up growth' is not statistically significantly different from IMVM fetuses presenting symmetric cortical maturation.