Normative linear and volumetric biometric measurements of fetal brain development in magnetic resonance imaging.

PURPOSE To provide normative two-dimensional and three-dimensional measurements of brain development in normal fetuses during the second and third trimester by a new semi-automated method. METHODS In this retrospective study, we included 98 normal fetuses at our institution between 21 and 38 weeks of gestation. Two-dimensional measurements of the brain were including biparietal diameter, occipitofrontal diameter, head circumference, transverse cerebellar diameter, and atrial diameter. Volumetric parameters were obtained by using ITK-SNAP software, including left and right cerebral hemispheres, lateral ventricle, the cerebellum, and extracerebral cerebrospinal fluid. RESULTS All linear and volume measurements were positively correlated with gestational age except for cerebrospinal fluid. Each anatomical region of the fetal brain showed a different relative growth rate. There was some volume asymmetry between the left and right lateral ventricles, and the left side was larger. The inter-observer and intra-observer agreement was excellent for all measures. CONCLUSION We established the 5th, 50th, and 95th percentile values of fetal brain volume measurements in magnetic resonance, and this may be helpful to understand the damage of fetal brain development.