The insulin-like growth factors (IGFs) are postulated to be altered in association with the development of intrauterine growth restriction (IUGR). The present studies examined placental and fetal hepatic mRNA concentration of components of the IGF system at two time points (55 and 90 d gestational age, dGA; Term 147 dGA) in a hyperthermia (HT)-induced sheep model of placental insufficiency-IUGR. Maternal plasma insulin and IGF-I were constant at 55 and 90 dGA and were unaffected by treatment. Umbilical vein insulin concentrations tended to be reduced at 90 dGA following HT exposure. Caruncle IGF-I mRNA was increased at 90 dGA in HT placentae (p < 0.05), while cotyledon concentrations were constant over gestation and unaltered by treatment. In control cotyledons, IGF-II mRNA concentration increased (p < 0.01) and IGFBP-3 decreased between 55 and 90 dGA (p < 0.01). Cotyledon IGF-II and caruncle IGFBP-4 mRNA were elevated at 55 dGA in HT placentae compared with control (p < 0.01 and p < 0.05 respectively). Fetal hepatic IGF-I, IGFBP-2, -3 and -4 concentrations rose over gestation (p < 0.05), but there were no treatment effects. These data suggest that changes in placental IGF expression in early and mid gestation may predispose the pregnancy to placental insufficiency, resulting in inadequate substrate supply to the developing fetus later in gestation.

Purpose: Analysis of fetal adipose tissue volumes may provide useful insight towards assessment of overall fetal health, especially in cases with abnormal fetal growth. Here, we assess whether fetal adipose tissue volume can be reliably measured using 3D water-fat MRI, using a quantitative assessment of the lipid content of tissues. Materials and methods: Seventeen women with singleton pregnancies underwent a fetal MRI and water-only and fat-only images were acquired (modified 2-point Dixon technique). Water and fat images were used to generate a fat signal fraction (fat/(water + fat)) from which subcutaneous adipose tissue was segmented along the fetal trunk. Inter-rater (three readers) and intrarater reliability was assessed using intraclass-correlation coefficients (ICC) for 10 image sets. Relationships between adipose tissue measurements and gestational age and estimated fetal weight percentiles were examined. Results: The ICC of the inter-rater reliability was 0.936 (p < .001), and the ICC of the intrarater reliability was 0.992 (p < .001). Strong positive correlations were found between adipose tissue measurements (lipid volume, lipid volume/total fetal volume, mean fat signal fraction) and gestational age. Conclusions: 3D water-fat MRI can reliably measure volume and quantify lipid content of fetal subcutaneous adipose tissues.

Placental dysfunction is associated with a decrease in nutrients and oxygen to the fetus; the gestational age at which this happens varies depending on severity but is an important factor in outcome as it relates to when and which brain structures are most at risk. Evidence from Doppler ultrasonography of fetuses affected by severe placental dysfunction leading to intrauterine growth restriction (IUGR) suggests blood flow distribution occurs in a hierarchical manner. In IUGR, oxygenated blood is directed toward the brain, away from other fetal organs (except the fetal heart), a process referred to as brain sparing. Further evidence suggests that subcortical regions critical for homeostasis receive more blood flow, at the cost of cortical regions involved in higher-order functions. Although Doppler findings suggest that cortical regions show more variability to placental oxygenation changes, a Cochrane review found that the evidence was of moderate to low quality,¹ indicating the need for more sensitive techniques to study how placental function affects the brain. Recent work has demonstrated an association between a magnetic resonance imaging (MRI)–based measure of placental oxygenation, transverse relaxation time (T2*), and birth weight,² suggesting that T2* may similarly estimate variations in fetal brain development.