Correction of Hypoxemia and Hypoglycemia Restores Muscle Mitochondrial Respiration and Remodels Mitochondrial Proteome in Growth-Restricted Sheep Fetuses

After completing this article, readers should be able to: Uteroplacental circulatory insufficiency (UPI) accounts for more than 70% of intrauterine growth restriction (IUGR) (1) and is associated with an increased risk of hypoxemic stress and nutritional deficiency. Both of these threats are concomitant and, to some extent, interrelated, but more importantly, both could lead to the feared complication of UPI—cerebral damage and secondary neurodevelopmental disabilities. To better appreciate the challenge involved in establishing the best time to deliver fetuses that have placental insufficiency, this article is divided in two parts. In the first section, present knowledge of the pathophysiology of fetal hypoxemia and nutritional deficiency in the context of UPI is reviewed briefly. The second section is devoted to a critical appraisal of the criteria currently applied to reach the decision that a fetus that has IUGR should be delivered.Fetal arterial oxygen (O2) concentrations are the result of relative proportions of blood that has different O2 saturations from various venous channels (the two venae cavae, the pulmonary veins, the coronary sinus, and the umbilical vein) draining into the cardiac cavities. Final arterial O2 saturation, therefore, predominantly is dictated by the volume of better-oxygenated blood arriving from the umbilical circulation. Normally, because of its low vascular resistance, the placenta accommodates 50% of the fetal combined cardiac output. Any change in this determinant part of venous return necessarily has a significant impact on intrauterine O2 delivery, even if Po2 in the umbilical vein is within normal range. Experimental (2)(3) and clinical (4)(5) investigations have established that UPI, which is associated with increased placental vascular resistance, causes fetal hypoxemia primarily by reducing umbilical blood flow. The fetus, however, still can maintain adequate cerebral oxygenation because of the many adaptive defense mechanisms summarized in the Table T1. (6) This condition corresponds to the “compensated phase” of hypoxemia. Nitric oxide appears to be an important factor, both in control of resting tone of the fetal cerebral vasculature (7) and as a mediator of the cerebral vasodilatory response to hypoxia. (8)The clinical and ultrasonographic features of the compensated phase of fetal hypoxemia are well-defined. Fetal weight gain is deficient but present. Results of conventional monitoring tools, such as nonstress testing (NST), computerized cardiotocogram (cCTG), and biophysical profile, (9) are all within the normal range. With Doppler monitoring, diastolic flow in the umbilical artery is either decreased or absent (Fig. 1A). The presence of an increased diastolic component in the middle cerebral artery is the rule, reflecting cerebral vasodilatation (Fig. 1B) and the so-called “brain-sparing effect.” At the level of the ductus venosus, the degree of red cell deceleration during atrial contraction (“a” wave) is usually within the normal range, confirming normal ventricular compliance (Fig. 1C). The physician can conclude with confidence that placental circulatory insufficiency is present with moderate hypoxemia but without cerebral hypoxia. The duration of moderate hypoxemic stress is, however, an additional element whose impact on postnatal life remains difficult to evaluate.In severe hypoxemia, the defense system is overwhelmed, resulting in metabolic acidemia and cerebral hypoxia. (10) The clinical and ultrasonographic features of this “decompensated phase” are well-documented. Fetal weight gain is nil or insignificant. Oligohydramnios usually is associated. The NST and cCTG show a reduction of fetal heart rate variability, and the biophysical profile is abnormal. In the umbilical artery, Doppler velocimetry shows either an absent or, more frequently, holodiastolic retrograde flow (Fig. 2A). Signs of cerebral vasodilatation are apparent (Fig. 2B). Ventricular diastolic dysfunction is expressed by an abnormally deep “a” wave on the ductus venosus, reaching the zero velocity line or sometimes being retrograde (Fig. 2C). In fetuses that have severe acidosis and are close to circulatory collapse, cerebral vasodilatation can disappear, heralding imminent fetal demise. (11)Fetal development depends on the availability of essential substrates that interact with the fetal genetic drive to growth. Oxygen, amino acids, and principally glucose have been shown to be major substrates for fetal growth and energy production. (12) Compelling evidence suggests that insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) play a major role in mediating the chain of metabolic events associated with fetal development. (13)(14)(15)(16) Expression of these growth factors can be modified by extrinsic influences such as nutrient supply and oxygen. Reduced nutrient availability is accompanied by a rapid and sustained decline of IGF bioactivity, at least in the rat. More disturbing is the observation in transgenic mice that the abnormal expression of IGFBP-1, an inhibitor of IGF action not normally expressed in the brain, results in suppression of brain growth. (17) Although species differences are possible, these data, transposed to the clinical setting, could mean that growth-restricted fetuses, even if delivered before the appearance of signs of hypoxic injury to the central nervous system, might still be at risk of neurodevelopmental disabilities and adverse health events in postnatal life. It is generally assumed, however, that the recirculation process that characterizes the “brain-sparing effect” of the compensated phase of hypoxemia by maintaining oxygen delivery to the brain (18) also should provide sufficient essential substrates for adequate brain development. (19) This would explain the asymmetric growth classically observed in such fetuses, characterized by diminished somatic growth and normal head size.Although oxygen and substrates might be satisfactorily supplied to the brain during the compensated phase of UPI, epidemiologic investigations into the long-term consequences of fetal nutrient deprivation indicate a higher incidence of diabetes, hypertension, and coronary artery disease among adults who were smaller than normal at birth. (20)(21)(22) Such findings strongly suggest interactions between genotype and the intrauterine environment, with resulting changes in gene expression. Finally, the widely accepted concept that reduced weight gain is part of the fetal defense system by decreasing oxygen consumption is flawed by the fact that hyperplastic development occurs in some vital organs strictly during the fetal period, especially the brain and the heart.IUGR, therefore, must be considered as the response to an inadequate environmental condition to ensure successful fetal survival, but this adaptive process can produce adverse fetal, neonatal, and adult consequences.Based on the pathophysiology of fetal nutritional deficits, evidence of growth restriction alone could be a valid indication for delivery to prevent the impact of fetal undernutrition on cardiovascular and metabolic diseases in adult life. However, systematic delivery of all fetuses that exhibit growth deficiency would increase significantly the incidence of preterm births and the well-known risks associated with prematurity. The Growth Restriction Intervention Trial evaluated the effect of early versus delayed delivery in the presence of abnormal umbilical artery Doppler velocimetry. (23)(24) The results of this multicenter study showed no significant difference in overall perinatal mortality rate between early and delayed delivery, resulting from increased fetal mortality associated with expectant management and increased neonatal mortality associated with early intervention. The median Griffith developmental quotient in survivors at 2 years of age was similar in both groups. Whether early delivery makes a difference in general health later in life remains to be elucidated.At present, it generally is agreed that as long as the “compensated phase” is efficient in maintaining adequate cerebral oxygenation, pregnancy prolongation is justified. Most attending perinatologists only intervene in the absence of a minimal weight gain or the appearance of signs of “decompensation.” The problem with this approach is that alterations in fetal heart rate (documented by NST, cCTG) and biophysical profile (fetal body movement and tone) are manifestations of central nervous system impairment and correlate well with the development of metabolic acidemia and intrauterine death, (25) which must be avoided. Furthermore, due to impressive improvements in the management of preterm neonates in recent decades, the survival rate is becoming less of an issue and no longer can be considered as the only outcome measure in the assessment of IUGR pregnancy management. In reality, among the offspring delivered to mothers according to conventional approaches, neurodevelopmental disabilities, including learning and attention deficits, behavioral disorders, and in severe cases, cerebral palsy and mental retardation, have been diagnosed in 30% to 50% of survivors. (26)Obviously, the optimal timing of delivery of fetuses that have IUGR should be based on reliable criteria that allow perinatologists to identify those that shortly will experience decompensation. These criteria should avoid too early delivery and extreme prematurity as well as too late fetal extraction, thus preventing the risk of prolonged exposure to nutrient deficits and hypoxic acidemia. Unfortunately, reliable criteria of impending decompensation in such fetuses currently are not available. (27)(28)The ratio between pulsatility indices of the umbilical and cerebral arteries, which reflects the “brain-sparing effect,” has been shown to be of little help in preventing neurologic abnormalities in fetuses that have IUGR. (29) Much now is being expected from venous Doppler velocimetry in the search for markers of impending breakdown of the fetal defense mechanism against hypoxemia. (30)(31)(32)(33) The flow velocity waveforms of the veins close to the heart are influenced by cyclic atrial pressures changes. Two forward waves are observed: one during atrial filling concomitant to ventricular systole (s wave), the other during the early part of diastole corresponding to ventricular relaxation (D wave). During the second part of diastole, atrial contraction causes a deceleration of the venous flow (“a” wave), which normally remains anterograde. The deepness of the “a” wave varies according to ventricular compliance, with lower compliance associated with a deeper “a” wave. When the loss of compliance is severe, the deceleration can reach the zero velocity line or even become retrograde. The major drawback with venous Doppler velocimetry is that it reflects the diastolic function of the myocardium, which is much more resistant to low oxygen supply than brain cells. Waiting for arbitrarily determined venous Doppler abnormalities to occur, therefore, might be too late in terms of brain integrity. The “brain-sparing effect” is another confounding element to interpretation of venous velocimetry because blood flow redistribution maintains normal or close to normal cerebral perfusion on the one hand and, consequently, normal venous return through the superior vena cava on the other hand. Meanwhile, increased placental vascular resistance and the secondary decline in placental blood flow, added to vasoconstriction of the mesenteric vascular network, decrease volume flow through the inferior vena cava. The resulting blood redistribution causes a deeper atrial deceleration wave in the inferior compared with the superior vena cava (34) without necessarily associated myocardial diastolic dysfunction. Although linkage of fetal arterial and venous Doppler velocimetry with fetal heart rate monitoring recently has been demonstrated to decrease the perinatal morbidity and mortality of fetuses that have IUGR, postnatal neurodevelopmental outcome of the survivors was not taken into consideration in these studies. (30)(35) The degree of changes in ductus venosus Doppler waveforms that would correspond to impending cerebral hypoxia is presently unknown. The answer could come from the TRUFFLE randomized trial comparing the results of deliveries based on cCGT with ductus venosus Doppler. (36)Experimental and clinical data support the incorporation of Doppler flow velocity waveforms through the aortic isthmus among the noninvasive markers of fetal well-being. (2)(37) The aortic isthmus is localized between the left subclavian artery perfused by the left ventricle and the ductus arteriosus perfused by the right ventricle. It represents the only link between the two parallel ventriculoarterial systems. Because of this unique anatomic position, isthmic flow velocity waveforms are influenced not only by downstream impedance of the subdiaphragmatic circulation but also by changes in arterial tone in the upper part of the body, especially the brain. In normal circumstances, due to the low resistance of the placental vascular bed, there is an antegrade flow in the isthmus during diastole. (38) In the presence of increased placental vascular resistance, changes in diastolic flow in the isthmus precede those in the umbilical artery, decreasing early in the process and rapidly becoming retrograde. (39)(40) When flow reverses in the aortic isthmus because of UPI, blood coming from the pulmonary artery and descending aorta is diverted from its normal destination (primarily the placenta), and the brain is partly perfused by blood deprived of placental or maternal substrates essential for its development and by red cells poorly saturated with oxygen. The greater the reverse isthmic flow, the higher the risk of prenatal cerebral damage. However, the dichotomized categorization of diastolic flow through the aortic isthmus (forward versus reverse) does not allow establishment of a cut-off point beyond which the risk of cerebral hypoxia is significantly increased. An isthmic flow index (IFI), therefore, was designed that takes into account the amount and direction of diastolic isthmus flow on a continuous scale. The IFI is obtained by dividing the sum of systolic and diastolic Doppler flow velocity integrals by systolic flow integrals (IFI=S+D/S). Normal values for this index were published recently. (41) Under normal conditions, systolic and diastolic flows are antegrade, and the IFI is always above 1. The IFI becomes equal to 1 when no flow is recorded during diastole in the isthmus with increased placental resistance. In more severe cases, reverse flow appears in diastole; the IFI is lower than 1 but is still positive because of the dominant forward flow in systole. In very severe cases, reverse diastolic flow is dominant, and the IFI is negative.Correlation between the IFI and the postnatal developmental outcome of 48 fetuses that had placental circulatory insufficiency was assessed in a pilot study. (37) All fetuses were delivered according to conventional criteria. An inverse correlation was found between the IFI and postnatal neurodevelopmental outcome. An IFI of 0.7 was suggested by this study as a cut-off value on which the decision to deliver could be based. However, a larger study is needed before reaching a final conclusion on this cut-off point. It is noteworthy that 16 of 35 fetuses considered to be in a safe zone (IFI >0.7) and theoretically protected from cerebral hypoxia manifested evidence of neurodevelopmental impairment. This observation could reinforce the concept that in growth-restricted fetuses, the integrity of the central nervous system depends not only on oxygen delivery but also on the sufficient availability of essential substrates.Timing delivery in pregnancies complicated by IUGR is a major issue that remains unresolved. To date, no single test can discriminate between fetuses that will benefit from immediate delivery and those that will profit from a more conservative approach. A combination of parameters, including gestational age, severity of IUGR, and results of prenatal testing, still is advocated by most investigators. Combined efforts of multidisciplinary groups of investigators should focus on finding noninvasive markers of impending cerebral hypoxia that would encompass both venous and arterial Doppler velocimetries. Emphasis should be placed on postnatal neurodevelopment and the general health status of the survivors, rather than on immediate fetal or neonatal survival.

Introduction and Methods: Placental insufficiency (PI) and fetal growth restriction (FGR) increases perinatal mortality and reduces postnatal productivity in livestock. Skeletal muscle constitutes a large proportion of tissue mass in the fetus, which is significantly reduced in the FGR fetus. This study investigates the effects of PI-FGR on musculoskeletal growth in sheep fetuses. Placental insufficiency and FGR (n = 8) was induced in pregnant ewes exposed to heat stress (35 to 40°C; RH 30-40%) between 40 and 95 days of gestation (term: 149 days). Control fetuses (n = 9) were from ewes maintained in thermoneutral conditions (20°C; RH 15-25%). At d120 ± 1, fetal surgeries were performed to place indwelling catheters for blood sampling. At d133 ± 1, umbilical blood flow was assessed before the fetuse was euthanized. Fetal hindlimb muscle satellite cells were isolated, and proliferation rates were assessed both in vivo and in vitro. Results: FGR fetuses had lower plasma glucose, insulin, IGF-1, and blood oxygen content (all P < 0.01). Absolute umbilical blood flow was lower in FGR fetuses (355 ± 41 vs. 619 ± 61 ml/min, P < 0.01), but weight-normalized blood flow was not different between groups. Both fetal weight (2118 ± 243 vs. 3423 ± 229 g) and placental weight (219 ± 41 vs. 426 ± 38 g) were lower (P < 0.01) in FGR fetuses. FGR fetuses exhibited higher brain-to-fetal (1.57 ± 0.06 vs. 1.34 ± 0.06, P = 0.01) and brain-to-liver weight ratios (0.85 ± 0.07 vs. 0.50 ± 0.06, P < 0.01), indicating brain sparing and asymmetrical growth. Hindlimb average muscle mass was reduced in FGR fetuses, including the biceps femoris (11.8 ± 2.2 vs. 18.4 ± 2.0 g, P = 0.04), semitendinosus (3.8 ± 0.7 vs. 6.3 ± 0.6 g, P = 0.01), gastrocnemius (7.7 ± 1.0 vs. 12.6 ± 1.0 g, P < 0.01), and tibialis anterior (3.4 ± 0.5 vs. 5.6 ± 0.5 g, P < 0.01). Muscle weights correlated (P < 0.01) with placental or fetal weights. In vivo, satellite cells proliferation rates were lower in FGR hindlimb muscle (3.8 ± 0.5 vs. 8.2 ± 1.5 %, P < 0.01). However, FGR isolated myoblasts had higher proliferation rates when cultured in nutrient enriched growth media (52 ± 0.5 vs. 48 ± 1.0 %, P < 0.01). Conclusion: FGR fetuses exhibited hypoglycemia, hypoxia, and reduced anabolic hormone concentrations, contributing to reduced hindlimb muscle mass. The contrast between lower satellite cell proliferation in vivo and increased proliferation in vitro under nutrient-enriched conditions suggests that nutrient deficiency and hypoxic stress are primary inhibitors of muscle cell growth in FGR fetal muscle. These results indicate that targeted nutrient or hormonal interventions may help restore muscle growth potential in FGR fetuses.

Maternal serum soluble fms-like tyrosine kinase-1–to–placental growth factor ratio distinguishes growth-restricted from non–growth-restricted small-for-gestational-age fetuses

Skeletal muscle atrophy in myotonic dystrophy type 1 (DM1) is caused by abnormal skeletal muscle satellite cell (SSC) proliferation due to increased glycolysis, which impairs muscle regeneration. In DM1, RNA foci sequester muscleblind-like protein 1 (MBNL1) in the nucleus, inhibiting its role in regulating SSC proliferation. Aerobic training reduces glycolysis and increases SSC proliferation and muscle fiber volume. This study aimed to investigate whether aerobic training prevents muscle atrophy in DM1 through the regulation of glycolysis via MBNL1. In this study, we used the HSALR transgenic mice (DM1 mice model) to investigate the effects of aerobic training on skeletal muscle atrophy and its molecular mechanisms. HSALR mice were subjected to 4 weeks of aerobic training. After aerobic training, hindlimb grip, and myofiber mean cross-sectional area (CSA) detected by haematoxylin and eosin (HE) staining were performed. In DM1 primary SSCs, cell proliferation was assessed using Pax7 and MyoD immunofluorescence and CCK-8 assays, RNA foci were detected by RNA fluorescence in situ hybridization, and total MBNL1 expression was measured by western blot. We also used lentivirus to knock down MBNL1 in DM1 primary SSCs and performed RNA sequencing and extracellular acidification rate (ECAR). Furthermore, glycolysis detected by ECAR and oxygen consumption rate (OCR) assays were performed in WT, Sedentary, and Training group SSCs. Glycolysis was inhibited with shikonin, a glycolysis inhibitor, and the proliferation of DM1 SSCs was subsequently evaluated. Finally, we engineered an adeno-associated virus specifically targeting MBNL1 to knock down MBNL1 in DM1 mice. Subsequently, we assessed hindlimb grip strength and CSA in vivo, as well as the glycolytic capacity and proliferative capacity of DM1 SSCs in vitro. Aerobic training increased hindlimb grip strength and the average myofiber CSA in DM1 mice. Additionally, aerobic training reduced RNA foci, upregulated MBNL1, and promoted SSC proliferation. Gene set enrichment analysis (GSEA) indicated that glycolytic processes were enriched following the knockdown of MBNL1. Furthermore, ECAR showed glycolysis was enhanced after the knockdown of MBNL1. Aerobic training reduced elevated glycolysis in DM1 mice and primary SSCs. Treatment with shikonin promoted DM1 SSC proliferation. However, MBNL1 knockdown was shown to abolish the reduced glycolysis and increased proliferation capability of SSCs due to aerobic training. Taken together, aerobic training suppresses glycolysis in SSCs via the upregulation of MBNL1, thereby enhancing SSC proliferation and alleviating muscle atrophy.

Abstract: Introduction and objective Placental insufficiency (PI) reduces fetal oxygen and glucose concentrations, leading to fetal growth restriction (FGR), decreased β-cell mass, and reduced insulin production. Single-cell RNA sequencing (scRNA-seq) of fetal sheep islets identified different stages of β-cell maturation. FGR fetuses exhibited a higher mature-to-immature β-cell ratio compared to controls. We tested the hypothesis that supplemental oxygen and glucose to FGR fetus normalizes the immature β-cell population. Methods PI-FGR was induced by maternal hyperthermia. The oxygen and glucose therapy was delivered via maternal oxygen insufflation and fetal glucose infusion (FGR-OG, n = 5) for 7-10 days. FGR-AS received air and saline infusions (n = 5) and control fetuses were developed under thermoneutral conditions (n = 3). Pancreatic islet cells were isolated for scRNA-seq (10X Genomics). Differential gene expression (DESeq2, P < 0.05) and pathway enrichment (KOBAS) were performed on the pseudo-bulked immature β-cell transcriptomes. Results FGR groups were growth restricted compared to controls (P < 0.01). The immature-to-mature β-cell ratio was reduced in FGR-AS islets (1.7:1) compared to control (5.7:1) and FGR-OG (8.7:1) islets. Transcriptomic analysis of immature β-cells from FGR-AS fetus revealed upregulation of ribosome, oxidative phosphorylation, proteosome, metabolic ­pathways, spliceosome and RNA polymerase compared to control β-cells. In contrast, oxidative phosphorylation, spliceosome, ribosome, and proteosome were downregulated in FGR-OG compared to FGR-AS β-cells. No enriched pathways were detected between control and FGR-OG β-cells. Conclusion FGR accelerates β-cell maturation based on the augmentation of gene expression in metabolic pathways. Moreover, immature β-cells in FGR-OG fetuses preserve the immature β-cell pool because their transcriptomic profile was similar to immature β-cells from control fetuses, which together indicates the oxygen glucose therapy partially rescue dysregulated metabolic programming in pancreatic β-cells. (Supported by NIH R01-DK084842)

Fetal growth restriction (FGR) increases the risk of cardiovascular disease. FGR is linked to placental insufficiency and fetal hypoxemia, leading to oxidative stress and inflammation, which collectively influence the developmental programming of cardiovascular disease. This study assessed whether melatonin (MLT), a potent antioxidant and anti‐inflammatory agent, could prevent cardiovascular deficits associated with FGR. Placental insufficiency was induced in ewes at 89 days of gestational age (dGA, term 148 dGA). Ewes were randomly allocated to control, FGR or FGR+MLT (i.v., 15 mg day−1, from 95 dGA to birth) groups. Lambs were delivered preterm at 136 dGA and assessed as newborn (24 h) and 4‐week‐old lambs. Vascular function was determined in femoral arteries using in vitro wire myography and vascular morphology as assessed in carotid and femoral arteries. Newborn FGR lambs were ∼30% smaller than control lambs with an increased brain‐to‐body weight ratio, indicative of brain sparing. Femoral endothelial function declined between ∼24 h after birth and 4 weeks in FGR lambs. By contrast, femoral arteries from newborn FGR+MLT lambs displayed transient endothelial dysfunction that improved by 4 weeks. However, these arteries showed elevated levels of oxidative stress and inflammation. Despite improving endothelial function, melatonin also disrupted the brain‐sparing response in FGR lambs. Furthermore, by 4 weeks of age, melatonin treatment led to heightened oxidative stress and inflammatory markers in the peripheral vasculature, suggesting a potential trade‐off between vascular benefits and systemic maladaptation. These findings highlight the complexity of melatonin's effects on the cardiovascular system and underscore the need for careful evaluation of its long‐term safety and efficacy before clinical translation.Key pointsFetal growth restriction (FGR) significantly increases the lifelong risk of cardiovascular disease, and there are currently no targeted treatments to mitigate these risks.This study follows growth‐restricted lambs from birth to 4 weeks of age (comparable to a 1‐year‐old human in terms of cardiovascular function) to characterise how FGR affects vascular development over time.FGR lambs exhibited progressive endothelial dysfunction in the femoral artery, but antenatal melatonin treatment restored endothelial function long‐term despite the presence of vascular oxidative stress and inflammation.The brain‐sparing response is a key adaptive mechanism for fetal survival, yet melatonin appears to dampen this response, highlighting the need for further investigation into its broader physiological effects.

Placental insufficiency lowers oxygen and glucose concentrations in the fetus, which causes fetal growth restriction (FGR). Previously we showed that FGR fetuses chronically supplemented with oxygen and glucose (OG) have improved glucose tolerance. However growth was not evaluated. Here we test the hypothesis that sustained OG supplementation to an FGR fetus will increase linear growth rates, raise anabolic hormone concentrations and promote proliferation rates in pancreatic β‐cells and skeletal muscle satellite cells, which are two tissues involved in glucose regulation. FGR was induced in sheep with environmental hyperthermia. FGR fetuses were chronically supplemented with either oxygen and glucose (FOG) or air and saline (FAS) for 10 days and compared to thermoneutral controls. Before supplementation both FOG and FAS fetuses had lower arterial oxygen, glucose, insulin and insulin‐like growth factor 1 (IGF‐1) concentrations compared to controls. The OG supplementation successfully increased PaO2, glucose and IGF‐1 concentrations, but amino acid concentrations were unaffected. On day 8 of supplementation glucose‐stimulated insulin concentrations were higher in FOG fetuses than FAS fetuses, whose insulin secretion was dependent on PaO2. Fetal thoracic circumference growth rates, which measure linear growth, for FOG and control fetuses were similar and greater than FAS rates. Although linear growth rates were normalized, body weights for FOG and FAS groups remained lighter than controls. However β‐cell and satellite cell proliferation rates were greater in FOG fetuses compared with FAS fetuses. Treatment of FGR with OG supplementation, two substrates transported across the placenta by diffusion, represents an innovative approach to reverse physiological challenges prenatally.New & NoteworthyExogenous supplementation with oxygen and glucose rescues critical features of fetal growth restriction (FGR) caused by placental insufficiency. For 10 days FGR sheep fetuses received oxygen and glucose, which increased fetal linear growth and anabolic hormone concentrations. Although fetal body weights remained lighter, the fetal therapy increased rates of β‐cell and satellite cell proliferation compared to untreated FGR fetuses. These results show promise in reversing fetal and cellular growth deficits associated with placental insufficiency.Key pointsSimultaneous supplementation of oxygen and glucose to fetuses with placental insufficiency successfully increased fetal arterial oxygen, glucose and IGF‐1 concentrations.Prenatal oxygen and glucose supplementation restored linear growth rates in growth‐restricted fetuses to levels similar to healthy controls, although overall body weight remained lower.Treatment increased the proliferation rates of pancreatic β‐cells and skeletal muscle satellite cells, addressing two key tissues that typically show reduced growth in untreated FGR fetuses.By the eighth day of supplementation FGR fetuses demonstrated improved glucose‐stimulated insulin secretion, indicating a functional recovery of pancreatic response.These findings suggest that targeting substrates transported across the placenta by diffusion – like oxygen and glucose – is an innovative approach to prenatally reverse the physiological challenges of placental insufficiency.

Guideline No. 442: Fetal Growth Restriction: Screening, Diagnosis, and Management in Singleton Pregnancies

Fetal growth restriction (FGR) increases the risk cardiovascular disease (CVD) in adulthood. Placental insufficiency and subsequent chronic fetal hypoxemia are causal factors for FGR, leading to a redistribution of blood flow that prioritizes vital organs. Subclinical signs of cardiovascular dysfunction are evident in growth-restricted neonates; however, the mechanisms programming for CVD in adulthood remain unknown. This study aimed to determine the potential mechanisms underlying structural and functional changes within the heart and essential (carotid) and nonessential (femoral) vascular beds in growth-restricted lambs. Placental insufficiency was surgically induced in ewes at 89 days gestational age (dGA, term = 148dGA). Three age groups were investigated: fetal (126dGA), newborn (24 h after preterm birth), and 4-wk-old lambs. In vivo and histological assessments of cardiovascular indices were undertaken. Resistance femoral artery function was assessed via in vitro wire myography and blockade of key vasoactive pathways including nitric oxide, prostanoids, and endothelium-dependent hyperpolarization. All lambs were normotensive throughout the first 4 wk of life. Overall, the FGR cohort had more globular hearts compared with controls (P = 0.0374). A progressive decline in endothelium-dependent vasodilation was demonstrated in FGR lambs compared with controls. Further investigation revealed that impairment of the prostanoid pathway may drive this reduction in vasodilatory capacity. Clinical indicators of CVD were not observed in our FGR lambs. However, subclinical signs of cardiovascular dysfunction were present in our FGR offspring. This study provides insight into potential mechanisms, such as the prostanoid pathway, that may warrant therapeutic interventions to improve cardiovascular development in growth-restricted newborns.NEW & NOTEWORTHY Our findings provide novel insight into the potential mechanisms that program for cardiovascular dysfunction in growth-restricted neonates as our growth-restricted lambs exhibited a progressive decline in endothelium-dependent vasodilation in the femoral artery between birth and 4 wk of age. Subsequent analyses indicated that this reduction in vasodilatory capacity is likely to be mediated by the prostanoid pathway and prostanoids could be a potential target for therapeutic interventions for fetal growth restriction (FGR).

Fetal growth restriction increases the risk of fetal and neonatal mortality and morbidity, and contributes to increased risk of chronic disease later in life. Intra-amniotic insulin-like growth factor-1 (IGF1) treatment of the growth-restricted ovine fetus improves fetal growth, but postnatal effects are unknown. Here we report that intra-amniotic IGF1 treatment of the growth-restricted ovine fetus alters size at birth and mechanisms of early postnatal growth in a sex-specific manner. We also show that maternal plasma C-type natriuretic peptide (CNP) products are related to fetal oxygenation and size at birth, and hence may be useful for non-invasive monitoring of fetal growth restriction. Intrauterine IGF1 treatment in late gestation is a potentially clinically relevant intervention that may ameliorate the postnatal complications of fetal growth restriction. Placental insufficiency-mediated fetal growth restriction (FGR) is associated with altered postnatal growth and metabolism, which are, in turn, associated with increased risk of adult disease. Intra-amniotic insulin-like growth factor-1 (IGF1) treatment of ovine FGR increases growth rate in late gestation, but the effects on postnatal growth and metabolism are unknown. We investigated the effects of intra-amniotic IGF1 administration to ovine fetuses with uteroplacental embolisation-induced FGR on phenotypical and physiological characteristics in the 2 weeks after birth. We measured early postnatal growth velocity, amino-terminal propeptide of C-type natriuretic peptide (NTproCNP), body composition, tissue-specific mRNA expression, and milk intake in singleton lambs treated weekly with 360μg intra-amniotic IGF1 (FGRI; n=13 females, 19 males) or saline (FGRS; n=18 females, 12 males) during gestation, and in controls (CON; n=15 females, 22 males). There was a strong positive correlation between maternal NTproCNP and fetal oxygenation, and size at birth in FGR lambs. FGR lambs were ∼20% lighter at birth and demonstrated accelerated postnatal growth velocity. IGF1 treatment did not alter perinatal mortality, partially abrogated the reduction in newborn size in females, but not males, and reduced accelerated growth in both sexes. IGF1-mediated upregulation of somatotrophic genes in males during the early postnatal period could suggest that treatment effects are associated with delayed axis maturation, whilst treatment outcomes in females may rely on the reprogramming of nutrient-dependent mechanisms of growth. These data suggest that the growth-restricted fetus is responsive to intra-amniotic intervention with IGF1, and that sex-specific somatotrophic effects persist in the early postnatal period.

Background Fetal growth restriction (FGR) is a condition characterized by the inability of the fetus to achieve its genetically determined growth potential, commonly defined by an ultrasonography-estimated fetal weight (EFW) below the 10th percentile for gestational age. Placental insufficiency is the leading cause of FGR, which is associated with significant short- and long-term morbidities, including adverse neurodevelopmental outcomes. Transcranial ultrasound (TCUS) remains a vital tool in neonatal neuroimaging due to its accessibility, cost-effectiveness, portability, and safety profile. It enables the evaluation of brain structures, including the cerebellar vermis, corpus callosum, fastigium, and ventricular system, providing insights into the cerebral effects of FGR. Objective To compare intracranial structures measurements of FGR neonates with those appropriate for gestational age (AGA) neonates using transcranial ultrasound. Methods This diagnostic accuracy study was conducted at the Neonatal Intensive Care Units (NICUs) of Children’s Hospital, Ain Shams University, Cairo, from December 2021 to June 2022. Ethical approval was obtained from the Ain Shams University Ethical Committee. The study enrolled 70 neonates, categorized into two groups: the FGR group (n = 35) with birth weights below the 10th percentile for gestational age, and the AGA group (n = 35) with birth weights between the 10th and 90th percentiles. Exclusion criteria included major cerebral congenital anomalies, Apgar scores <7 at 5 minutes, prolonged hypoglycemia, metabolic acidosis (pH < 7.25), and genetic syndromes associated with low birth weight.Maternal and neonatal characteristics as maternal age, diseases, infections and placental problems and neonatal gestational age, Anthropometric measurements, diagnosis and hospitalization in NICU were recorded, and transcranial ultrasound was performed to measure intracranial structures, including corpus callosum length, cerebellar vermis height, transverse cerebellar diameter (TCD), and ventricular dimensions. Results The study population consisted of 35 FGR neonates (18 females, 17 males) and 35 AGA neonates (20 females, 15 males). FGR was significantly associated with maternal hypertension (p < 0.001) and placental insufficiency (p < 0.001). Compared to AGA neonates, FGR neonates had significantly lower gestational age (34.06±2.14 weeks vs. 35.43±2.52 weeks, p = 0.017). The measurements showed preterm neonates were more affected than full term ones in both FGR and AGA groups. Longitudinal assessments revealed a significant decline in transcranial measurements in FGR neonates, in contrast to the stable or increasing trends observed in AGA neonates. Among FGR neonates, symmetrical FGR was associated with relatively smaller brain dimensions compared to asymmetrical FGR in specific parameters of transcranial measurements. Conclusion This study underscores the significant impact of FGR on neonatal intracranial development, with notable differences in brain structure measurements compared to AGA neonates. FGR was strongly associated with maternal hypertension, placental insufficiency, and adverse neonatal growth parameters. These findings highlight the critical role of maternal health in fetal neurodevelopment and emphasize the need for targeted antenatal and postnatal interventions to improve outcomes in FGR-affected neonates.

Fetal cardiac remodeling and dysfunction is associated with both preeclampsia and fetal growth restriction

Considering evidence in the management of fetal growth restriction.

Fetal growth restriction (FGR) caused by placental insufficiency is characterized by fetal hypoxemia and elevated catecholamines. We hypothesized that the catecholamine metabolites homovanillic acid (HVA) and vanillylmandelic acid (VMA) would be elevated in a sheep model of placental insufficiency and FGR. We measured HVA and VMA in fetal arterial plasma and amniotic fluid and analyzed their relationships with fetal weight, sex, and concentrations of fetal arterial norepinephrine (NE), oxygen, insulin, and IGF-1. Compared to controls, FGR fetuses had higher arterial plasma concentrations of HVA (39%), VMA (53%), and NE (369%), and lower arterial blood oxygen (26%) and plasma insulin (62%) and IGF-1 (59%). Fetal arterial HVA and VMA were positively correlated with NE and inversely correlated with fetal oxygen and IGF-1 concentrations and fetal weight. Amniotic fluid concentrations of HVA and VMA were also elevated in FGR fetuses. These findings support HVA and VMA as biochemical markers of chronically elevated fetal catecholamine concentrations, with potential utility for identifying fetuses with chronic hypoxemia. The presence of these metabolites in amniotic fluid also suggests the feasibility of non-invasive assessment at the time of or shortly after birth. This manuscript identifies homovanillic acid (HVA) and vanillylmandelic acid (VMA) as biochemical markers of chronic fetal hypoxemia in a sheep model of FGR and are elevated in both plasma and amniotic fluid of FGR fetuses. These data demonstrate strong correlations between HVA/VMA and fetal NE, oxygen content, IGF-1, and fetal weight. This work supports future studies assessing HVA/VMA as potential non-invasive biomarkers in amniotic fluid sampled at delivery to improve newborn risk stratification beyond size-based criteria.

Fetal growth restriction (FGR) is defined as the failure of the fetus to meet its growth potential due to a pathological factor, most commonly placental dysfunction. Worldwide, FGR is a leading cause of stillbirth, neonatal mortality, and short- and long-term morbidity. Ongoing advances in clinical care, especially in definitions, diagnosis, and management of FGR, require efforts to effectively translate these changes to the wide range of obstetric care providers. This article highlights agreements based on current research in the diagnosis and management of FGR, and the areas that need more research to provide further clarification of recommendations. The purpose of this article is to provide a comprehensive summary of available evidence along with practical recommendations concerning the care of pregnancies at risk of or complicated by FGR, with the overall goal to decrease the risk of stillbirth and neonatal mortality and morbidity associated with this condition. To achieve these goals, FIGO (the International Federation of Gynecology and Obstetrics) brought together international experts to review and summarize current knowledge of FGR. This summary is directed at multiple stakeholders, including healthcare providers, healthcare delivery organizations and providers, FIGO member societies, and professional organizations. Recognizing the variation in the resources and expertise available for the management of FGR in different countries or regions, this article attempts to take into consideration the unique aspects of antenatal care in low-resource settings (labelled “LRS” in the recommendations). This was achieved by collaboration with authors and FIGO member societies from low-resource settings such as India, Sub-Saharan Africa, the Middle East, and Latin America.