Evaluation of changes in biochemical composition of fetal brain between 18th and 40th gestational week in proton magnetic resonance spectroscopy.

INTRODUCTION: The aim of this study is to determine the right 1 H MRS spectra of the brain in fetuses of different age, and then to define what metabolic changes occur between 18th and 40th weeks of pregnancy.

METHODS: 1 H MRS studies of 32 fetuses aged 18-40 gestational weeks were performed, in which the MRI excluded central nervous system malformations. The studied group included 11 fetuses aged 18-25 weeks (the second half of the second trimester), 14 fetuses aged 26-33 weeks (the first half of the third trimester), and seven fetuses aged 34-40 weeks (the second half of the third trimester). The relative ratios of metabolites concentrations to the sum of all metabolites were calculated.

RESULTS: Increase in the concentrations of N-acetylaspartate (NAA), Cr, Cho, and myo-inositol (mI) with gestational age is statistically significant. Only increase in Glx is statistically insignificant. In the analyzed period of pregnancy also, an insignificant increase of NAA/Σ and Cr/Σ ratios and a decrease of mI/Σ, Cho/Σ and Glx/Σ ratios were noticed.

CONCLUSIONS: Changes in the 1 H MRS spectrum are visible with increasing age of the fetus. All studied substances in fetal brain change their concentrations during pregnancy, which may be associated with the synaptic and dendritic development as well as myelination. Knowledge about the chemical changes in the fetal brain can provide valuable information in studies of the mechanisms of pregnancy and fetal development, define steps of brain metabolic development and explain reasons of pathologies.