[Growth of the fetal cerebellum in normal pregnancy].
An ultrasonographic study was carried out in 203 physiological pregnancies whose menstrual gestational age (MGA) was between 20 and 40 weeks. The following biometric parameters were determined: transversal cerebellar diameter (TCD), biparietal diameter (BPD), occipito-frontal diameter (OFD) and head circumference (HC). The data analysis gave the optimal mathematical models with the following relations: 1) TCD/MGA (R2 = 0.904; SD = 2.6 mm); 2) MGA/TCD (R2 = 0.924; SD = 1.7 wks); 3) BPD/TCD (R2 = 0.914; SD = 4.3 mm); 4) HC/TCD (R2 = 0.919; SD = 14.3 mm), which are graphically and tabularly presented. Also the variability in the determination of MGA from TCD is calculated before 26 weeks (2 SD = 2.6 wks) and after 26 weeks (2 SD = 3.5 wks). TCD can be practically applied in cases where it is difficult or impossible to measure BPD, or in cases where it is unsuitable because of the expressed moulding of the head, since the cerebellum is not liable to changes in forms and its size is in correlation with MGA and BPD. The use of TCD is also important in the detection of congenital malformations which are manifested in the posterior cranial fossa. The potential importance of TCD in the diagnosis of the fetal intrauterine growth retardation is based on the assumption that the cerebellum is not liable, or at least not considerably liable, for growth retardation.