Background: Despite its many advantages, experience with fetal magnetic resonance imaging (MRI) is limited, as is knowledge of how fetal tissue relaxation times change with gestational age (GA). Quantification of fetal tissue relaxation times as a function of GA provides insight into tissue changes during fetal development and facilitates comparison of images across time and subjects. This, therefore, can allow the determination of biophysical tissue parameters that may have clinical utility. Purpose: To demonstrate the feasibility of quantifying previously unknown T 1 and T 2 * relaxation times of fetal tissues in uncomplicated pregnancies as a function of GA at 1.5 T. Study Type: Pilot. Population: Nine women with singleton, uncomplicated pregnancies (28-38 weeks GA). Field Strength/Sequence: All participants underwent two iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL-IQ) acquisitions at different flip angles (6 and 20 ) at 1.5 T. Assessment: Segmentations of the lungs, liver, spleen, kidneys, muscle, and adipose tissue (AT) were conducted using water-only images and proton density fat fraction maps. Driven equilibrium single pulse observation of T 1 (DESPOT 1 ) was used to quantify the mean water T 1 of the lungs, intraabdominal organs, and muscle, and the mean water and lipid T 1 of AT. IDEAL T 2 * maps were used to quantify the T 2 * values of the lungs, intraabdominal organs, and muscle. Statistical Tests: F-tests were performed to assess the T 1 and T 2 * changes of each analyzed tissue as a function of GA. Results: No tissue demonstrated a significant change in T 1 as a function of GA (lungs [P = 0.

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Observing fetal development in utero is vital to further the understanding of later-life diseases. Magnetic resonance imaging (MRI) offers a tool for obtaining a wealth of information about fetal growth, development, and programming not previously available using other methods. This review provides an overview of MRI techniques used to investigate the metabolic and cardiovascular consequences of the developmental origins of health and disease (DOHaD) hypothesis. These methods add to the understanding of the developing fetus by examining fetal growth and organ development, adipose tissue and body composition, fetal oximetry, placental microstructure, diffusion, perfusion, flow, and metabolism. MRI assessment of fetal growth, organ development, metabolism, and the amount of fetal adipose tissue could give early indicators of abnormal fetal development. Noninvasive fetal oximetry can accurately measure placental and fetal oxygenation, which improves current knowledge on placental function. Additionally, measuring deficiencies in the placenta’s transport of nutrients and oxygen is critical for optimizing treatment. Overall, the detailed structural and functional information provided by MRI is valuable in guiding future investigations of DOHaD.

Myelin water fraction (MWF), a validated marker for myelin lipid, can be used to assess fetal myelination in vivo. Thus, this study aims to demonstrate the feasibility of quantifying fetal MWF. 11 pregnant guinea pigs with 38 fetuses were imaged in a 3T MRI. mcDESPOT was used to quantify MWF in the corpus callosum (CC) of the maternal brain and the CC and fornix (FOR) of the fetal brain. MWF maps were successfully generated in all fetal brains, confirming its feasibility. Maternal MWF results and comparison of fetal CC and FOR MWF results are consistent with published results.

Intrauterine growth restriction (IUGR) is an obstetrical outcome where a fetus has not achieved its genetic potential. A consequence of IUGR is a decrease in brain myelin content. Myelin water imaging (MWI) has previously assessed fetal myelin water fraction (MWF) and can potentially assess myelination changes associated with IUGR. Thus, this study aims to quantify and compare the MWF of non-IUGR and IUGR fetal guinea pigs (GPs) in late gestation. Our sample consisted of 22 pregnant Dunkin-Hartley GPs with 71 fetuses (34 male) [mean ± standard deviation: 60 ± 1.2 days gestation]. Eight SPGR volumes [flip angles (α): 2° — 16°], and two sets of 8 bSSFP volumes (α: 8° — 64°), at 0° and 180° phase increments were acquired at 3.0 T. MWF maps were generated for each fetal GP brain using multicomponent driven equilibrium single pulse observation of T1/T2(mcDESPOT). Regions of interest (ROIs) were placed in the fetal corpus callosum (CC), fornix (FOR), and parasagittal white matter (PSW). Linear regression was performed between five fetal IUGR markers [body volume (BV), body–to–pregnancy volume ratio (BPrVR), brain–to–liver VR (BLVR), brain–to–placenta VR (BPlVR), and brain–to–BVR (BBVR)] and MWF for all regions (coefficient of determination, R2). A t–test with a linear mixed model compared the MWF of non–IUGR and IUGR fetal GPs for all three regions (α = 0.05). The MWF values are as follows: (mean ± standard deviation): 0.23 ± 0.02 (fetal CC), 0.19 ± 0.02 (fetal CC — IUGR), 0.31 ± 0.02 (fetal FOR), 0.27 ± 0.01 (fetal FOR — IUGR), 0.28 ± 0.02 (fetal PSW), and 0.24 ± 0.03 (fetal PSW — IUGR). Significant differences in MWF were found between the non–IUGR and IUGR fetuses in every region. In conclusion, the mean MWF of IUGR fetal GPs is significantly lower than non–IUGR fetal GPs.