Volumetric Brain MRI Study in Fetuses with Intrauterine Growth Restriction Using a Semiautomated Method

Fetal brain development in fetal growth restriction using MRI: a systematic review

BACKGROUND

This systematic review investigates potential differences in brain development between growth restricted (FGR)-fetuses compared to appropriate for gestational age (AGA) fetuses using MRI.

METHODS

PubMed, Embase, Cochrane Library and Web of Science databases were searched from 1985 to 2023. FGR was defined as an estimated fetal weight (EFW) < p10 and/or an abdominal circumference (AC) < p10, or 20% reduction in EFW or AC using a minimum interval of two weeks. Outcomes included volumetrics, biometrics, apparent diffusion coefficients (ADC), 1H-MRS-metabolites, and oxygenation of the fetal brain. Risk of bias was assessed using Newcastle-Ottawa Scale (NOS). A meta-analysis was conducted on variables when reported in at least three studies, calculating the mean difference (MD) with a 95% confidence interval (CI).

RESULTS

Twenty-nine studies were included after three-phase screening, 13 used the FGR consensus definition according to the Delphi procedure. Total brain volume and cerebellar volume were significantly reduced in FGR fetuses (n = 183; 74) when compared to AGA fetuses (n = 283; 166) with a MD of -30.84 cm3 (p < 0.01) and - 2.24 cm3 (p < 0.01). ADC values in the frontal white matter (FWM), occipital white matter (OWM), temporal white matter (TWM), thalami, centrum semiovale (CSO), basal ganglia, pons and cerebellum, significantly lower in growth restricted fetuses (-0.07 × 10-3 mm2/s (p < 0.01); -0.06 × 10-3 mm2/s (p < 0.01); -0.07 × 10-3 mm2/s (p < 0.01); -0.10 × 10-3 mm2/s (p < 0.01); -0.06 × 10-3 mm2/s (p < 0.01); -0.07 × 10-3 mm2/s (p < 0.01); -0.07 × 10-3 mm2/s (p < 0.01); -0.02 × 10-3 mm2/s (p < 0.01); respectively). 1H-MRS showed reduced levels of N-acetyl aspartate (NAA): Choline (Cho) and NAA: Creatine(CR) levels in the frontal lobe and central brain tissue, whilst contradictive findings concerning Cho: Cr and Inositol(Ino): Cho ratios were found. Two studies investigated the cerebral hemodynamic changes in FGR fetuses showing no difference in fractional moving blood volume, similar venous blood oxygenation in the superior sagittal sinus and no difference in T2* in the fetal brain.

DISCUSSION

MRI provides additional information on fetal brain development in a growth restricted population. Smaller total brain and cerebellar volumes and lower ADC values in the FWM, OWM, TWM, thalami, CSO, basal ganglia, pons and cerebellum have been observed in FGR. These conclusions are drawn on relatively small sample sizes with high heterogeneity resulting from diverse study populations and MRI techniques. Furthermore, how these findings correlate to long-term neurocognitive abnormalities associated with FGR remains to be elucidated. A large cohort study comparing brain maturation, myelination, metabolic and hemodynamic status between brain-sparing FGR fetuses to healthy age-matched controls is needed.

Neuroprotective effects of maternal melatonin administration in early-onset placental insufficiency and fetal growth restriction

BACKGROUND

Early-onset fetal growth restriction (FGR) is associated with adverse outcomes. We hypothesised that maternal melatonin administration will improve fetal brain structure in FGR.

METHODS

Surgery was performed on twin-bearing ewes at 88 days (0.6 gestation), and FGR induced in one twin via single umbilical artery ligation. Melatonin was administered intravenously (6 mg/day) to a group of ewes commencing on day of surgery until 127 days (0.85 gestation), when the ewe/fetuses were euthanized, and fetal brains collected.

RESULTS

Study groups were control (n = 5), FGR (n = 5), control+melatonin (control+MLT; n = 6) and FGR+melatonin (FGR + MLT; n = 6). Melatonin administration did not significantly alter fetal body or brain weights. Myelin (CNPase+) fibre density was reduced in FGR vs. control animals in most brain regions examined (p < 0.05) and melatonin treatment restored CNPase fibre density. Similar but less pronounced effect was seen with mature myelin (MBP+) staining. Significant differences in activated microglia (Iba-1) activity were seen between lamb groups (MLT mitigated FGR effect) in periventricular white matter, subventricular zone and external capsule (p < 0.05). Similar effects were seen in astrogliosis (GFAP) in intragyral white matter and cortex.

CONCLUSIONS

Maternal melatonin administration in early onset FGR led to improved myelination of white matter brain regions, possibly mediated by decreased inflammation.

IMPACT

Maternal melatonin administration might lead to neuroprotection in the growth-restricted fetus, possibly via dampening neuroinflammation and enhancing myelination. This preclinical study adds to the body of work on this topic, and informs clinical translation. Neuroprotection likely to improve long-term outcomes of this vulnerable infant group.

Fetal brain volumes and neurodevelopmental outcome of intrauterine growth restricted fetuses

OBJECTIVE

This study aims to investigate the correlation of MRI measured fetal brain volumetrics with long-term neurodevelopmental outcome, among intrauterine growth restricted (IUGR) and apparently healthy fetuses.

STUDY DESIGN

A historical cohort study at a single tertiary referral medical center during 6 years period, of fetuses diagnosed with IUGR due to placental insufficiency, and apparently healthy fetuses, who had fetal brain MRI scan. The volumes of the supratentorial brain region, both hemispheres and the cerebellum were measured by 3D MRI semi-automated volume measurements. The cerebellar to supratentorial ratio (CER/ST) was calculated. Volumes were plotted on normal growth curves. 17 IUGR fetuses, and 53 apparently healthy fetuses adhered to participate in the VABS-II questionnaire, evaluating neurodevelopmental outcome.

RESULTS

70 patients (mean age at conducting VABS-II questionnaire 4.4 ± 2.1 years, 38 males) were evaluated. Among fetuses born in a gestational age of 36 weeks or later, IUGR fetuses demonstrated a significantly larger number of abnormal results in the VABS-II communication domain (p =.049). No significant differences were found in other domains or in overall neurodevelopmental outcome. The CER/ST ratio correlated with the overall neurodevelopmental outcome of the total study population (r = 0.40, p <.001), and of the IUGR group separately (ρ = 0.58, p =.02).

CONCLUSION

CER/ST ratio measured using fetal brain MRI was found to be correlated with long term neurodevelopmental outcome. This result may aid in clinical interpretation of biometric data obtained by fetal brain MRI, linking it with long term neurodevelopmental outcome.

3D T2w fetal body MRI: automated organ volumetry, growth charts and population-averaged atlas

Structural fetal body MRI provides true 3D information required for volumetry of fetal organs. However, current clinical and research practice primarily relies on manual slice-wise segmentation of raw T2-weighted stacks, which is time consuming, subject to inter- and intra-observer bias and affected by motion-corruption. Furthermore, there are no existing standard guidelines defining a universal approach to parcellation of fetal organs. This work produces the first parcellation protocol of the fetal body organs for motion-corrected 3D fetal body MRI. It includes 10 organ ROIs relevant to fetal quantitative volumetry studies. We also introduce the first population-averaged T2w MRI atlas of the fetal body. The protocol was used as a basis for training of a neural network for automated organ segmentation. It showed robust performance for different gestational ages. This solution minimises the need for manual editing and significantly reduces time. The general feasibility of the proposed pipeline was also assessed by analysis of organ growth charts created from automated parcellations of 91 normal control 3T MRI datasets that showed expected increase in volumetry during 22-38 weeks gestational age range. In addition, the results of comparison between 60 normal and 12 fetal growth restriction datasets revealed significant differences in organ volumes.