The changing Doppler patterns and perinatal outcomes of monochorionic diamniotic twins with selective fetal growth restriction.

OBJECTIVES: To investigate the clinical outcomes and Doppler patterns changes in monochorionic diamniotic (MCDA) twins with selective fetal growth restriction (sFGR). METHODS: We retrospectively analyzed 362 sFGR cases from January 2010 to May 2016 at a single tertiary referral center. The Doppler waveforms of umbilical artery end-diastolic flow were collected, and all neonates were subjected to an early neonatal brain scan. RESULTS: A total of 66/100 (66 %) type I cases were stable, whereas 25/100 (25 %) cases changed to type II and 9/100 (9 %) changed to sFGR complicated twin-twin transfusion syndrome (TTTS). A total of 48.9 % (22/45) sFGR cases were complicated with polyhydramnios and 30.4 % (7/23) sFGR cases were complicated with oligohydramnios, both of which were progressed to sFGR with TTTS. Mild cerebral injury was significantly associated with Doppler flow abnormalities, earlier gestational age at delivery and type of sFGR diagnosis. Severe cerebral injury was significantly associated with gestational age at delivery (31.6 vs. 34.1, p=0.002) and larger birthweight discordance (43.9 vs. 29.3 %, p=0.011). CONCLUSIONS: Doppler patterns in sFGR can gradually change, with important consequences with regard to management and outcomes. Along with abnormal Doppler findings, earlier occurrence of sFGR and delivery are associated with subsequent neonatal cerebral injury.

Effects of umbilical vein flow on midbrain growth and cortical development in late onset fetal growth restricted fetuses: a prospective cross-sectional study.

OBJECTIVES: To investigate midbrain growth, including corpus callusum (CC) and cerebellar vermis (CV) and cortical development in late fetal growth restricted (FGR) subclassified according to the umbilical vein blood flow (UVBF) values. METHODS: This was a prospective study on singleton fetuses late FGR with abnormal placental cerebral ratio (PCR). FGR fetuses were further subdivided into normal (≥fifth centile) and abnormal (

Detecting abnormal placental microvascular flow in maternal and fetal diseases based on flow-compensated and non-compensated intravoxel incoherent motion imaging.

INTRODUCTION: Intravoxel Incoherent Motion (IVIM) imaging has been used to assess placental microcirculatory flows. We proposed a joint analysis of flow-compensated (FC) and non-compensated (NC) diffusion MRI to estimate the fraction and velocity of ballistic microcirculatory flow (fb and vb), and evaluated the diagnostic performance of the new markers in maternal and fetal disorders. METHODS: Gestational diabetes mellitus (GDM, n = 15) pregnancies and fetal growth restriction (FGR, n = 12), along with gestational age matched normal controls (n = 19 for GDM and 15 for FGR) underwent FC and NC-encoded IVIM scans at 1.5 T. fb and vb obtained from a FC-NC joint model, along with the conventional IVIM indices, were compared between patient groups for whole-placenta and maternal/fetal sides of the placenta. A linear support vector machine (SVM) was used to classify the GDM, FGR and controls. RESULTS: vb of whole-placenta were significantly lower in both GDM (p = 0.017) and FGR (p = 0.043), compared with their controls, and the differences were more evident in the fetal side (p = 0.010 for GDM and p = 0.042 for FGR). fb and fFC showed group differences in the fetal side and DFC showed differences in whole-placenta for GDM patients. In the classification task, vb showed the highest diagnostic accuracy of 70.6% for GDM and 63.0% for FGR, and the combination of fb and vb further improved the detection accuracy to 73.5% and 66.7% for GDM and FGR, respectively. DISCUSSION: vb showed superior performance in the diagnosis of GDM and FGR, indicating the potential of the joint FC-NC IVIM method for placenta examinations.

Association of the maternal serum albumin level with fetal growth and fetal growth restriction in term-born singletons: a prospective cohort study.

OBJECTIVE: To investigate the association of the maternal serum albumin (MAlb) level with fetal growth and fetal growth restriction (FGR) risk in term-born singletons. DESIGN: Prospective cohort study. SETTING: Four hospital maternity units of the Tongji Maternal and Child Health Cohort study initiated from September 2013 to April 2016 at Wuhan City, in central China. PATIENT(S): A total of 3,065 mother-offspring pairs. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Fetal growth was evaluated by birth weight (BW) and birth length. Fetal growth restriction was defined as BW below the 10th percentile. RESULT(S): All MAlb levels were within the upper limit of normal. After adjustment for liver function parameters, inflammatory indicators, and others, a reverse U-shaped relationship between MAlb and fetal growth was observed. Specifically, BW increased significantly with an increasing MAlb level when the MAlb level was <36.1 g/L (per g/L: ß = 36.8; 95% CI, 0.8, 72.7) but decreased with increasing the MAlb level when the MAlb level was >36.1 g/L (per g/L: ß = -15.1; 95% CI, -21.2, -8.9). There was a similar association between MAlb and birth length. Furthermore, the adjusted odd ratios of FGR across increasing tertiles of the MAlb levels were 1.0 (reference), 1.1 (0.7, 1.8), and 1.7 (1.0, 2.6). CONCLUSION(S): There was a reverse U-shaped association between MAlb and fetal growth. A higher MAlb level was associated with an increased risk of FGR. CLINICAL TRIAL REGISTRATION NUMBER: NCT03099837.

S100B in maternal circulation of pregnancies complicated by FGR and brain sparing.

OBJECTIVE: To determine whether the presence of brain sparing in fetal growth restricted (FGR) fetuses involves elevation of the cerebral injury biomarker S100B in maternal circulation. METHODS: We included 63 women with suspected small for gestational age (SGA) fetuses between 24 and 35 +6/7 weeks of gestation. Maternal plasma angiogenic factors measurements and sonographic evaluation were performed at recruitment. Next, we subdivided our SGA cohort into three groups: SGA fetuses, FGR fetuses without brain-sparing, and FGR fetuses with brain-sparing (FGR-BS). Serum S100B concentration was calculated as S100B µg/L, S100B MoM, and the ratio S100B/ estimated fetal weight (EFW). We also report one case of S100B concentration surge in maternal serum following the diagnosis of fetal intraventricular hemorrhage (IVH). RESULTS: The FGR-BS group had higher maternal S100B µg/L (p < 0.01, p < 0.05, respectively), S100B MoM (p < 0.001, p < 0.001, respectively), and S100B/EFW (p < 0.001, p < 0.01, respectively), compared to the SGA and FGR groups. In the case report, maternal serum S100B concentrations were 0.0346 µg/L before, and 0.0874 µg/L after IVH occurrence. CONCLUSIONS: S100B concentration in maternal serum increased in pregnancies complicated by FGR and brain sparing. These results may substantiate in-utero cerebral injury and may explain the adverse neurocognitive outcomes reported for this group.

The role of the brain-sparing effect of growth-restricted fetuses in newborn germinal matrix/intraventricular hemorrhage.

OBJECTIVES: The aim of the study was to evaluate the effect of the brain-sparing effect (BSE) of fetal growth restriction (FGR) in newborn germinal matrix/intraventricular hemorrhage (GM/IVH). METHODS: A total of 320 patients who delivered prior to the 34th gestational week were analyzed from data records. 201 patients were divided into two groups according to cerebro-placental ratio (CPR): early fetal growth restriction (FGR) with abnormal CPR group (n=104) and appropriate for gestational age with normal Doppler group (control) (n=97). Using the normal middle cerebral artery (MCA) Doppler as a reference, multivariate logistic regression analysis was used to assess the association between the BSE and the primary outcome. RESULTS: The rate of Grade I-II germinal matrix/intraventricular hemorrhage (GM/IVH) was 31(29.8%) in the group possessing early FGR with abnormal CPR and 7(7.2%) in the control group, showing a statistically significant difference. The rate of grade III-IV GM/IVH was 7(6.7%) in the group possessing early FGR with abnormal CPR and 2 (2.1%) in the control group, showing no statistically significant difference. We found that gestational age at delivery <32 weeks was an independent risk factor for GM/IVH. In addition, we found that other variables such as the presence of preeclampsia, fetal weight percentile <10, emergency CS delivery, 48-h completion after the first steroid administration and 24-h completion rate after MgSO4 administration were not independently associated with the primary outcome. CONCLUSIONS: Our results indicate that the rate of GM-IVH was increased in the group possessing early FGR with abnormal CPR; however, multivariate logistic regression analysis showed that BSE was not an independent risk factor for GM/IVH.

Fetal growth restriction impairs hippocampal neurogenesis and cognition via Tet1 in offspring.

Fetal growth restriction (FGR) increases the risk for impaired cognitive function later in life. However, the precise mechanisms remain elusive. Using dexamethasone-induced FGR and protein restriction-influenced FGR mouse models, we observe learning and memory deficits in adult FGR offspring. FGR induces decreased hippocampal neurogenesis from the early post-natal period to adulthood by reducing the proliferation of neural stem cells (NSCs). We further find a persistent decrease of Tet1 expression in hippocampal NSCs of FGR mice. Mechanistically, Tet1 downregulation results in hypermethylation of the Dll3 and Notch1 promoters and inhibition of Notch signaling, leading to reduced NSC proliferation. Overexpression of Tet1 activates Notch signaling, offsets the decline in neurogenesis, and enhances learning and memory abilities in FGR offspring. Our data indicate that a long-term decrease in Tet1/Notch signaling in hippocampal NSCs contributes to impaired neurogenesis following FGR and could serve as potential targets for the intervention of FGR-related cognitive disorders.

ACE2: a key modulator of the renin-angiotensin system and pregnancy.

Angiotensin-converting enzyme 2 (ACE2) is a membrane-bound protein containing 805 amino acids. ACE2 shows approximately 42% sequence similarity to somatic ACE but has different biochemical activities. The key role of ACE2 is to catalyze the vasoconstrictor peptide angiotensin (ANG) II to Ang-(1-7), thus regulating the two major counterbalancing pathways of the renin-angiotensin system (RAS). In this way, ACE2 plays a protective role in end-organ damage by protecting tissues from the proinflammatory actions of ANG II. The circulating RAS is activated in normal pregnancy and is essential for maintaining fluid and electrolyte homeostasis and blood pressure. Renin-angiotensin systems are also found in the conceptus. In this review, we summarize the current knowledge on the regulation and function of circulating and uteroplacental ACE2 in uncomplicated and complicated pregnancies, including those affected by preeclampsia and fetal growth restriction. Since ACE2 is the receptor for SARS-CoV-2, and COVID-19 in pregnancy is associated with more severe disease and increased risk of abnormal pregnancy outcomes, we also discuss the role of ACE2 in mediating some of these adverse consequences. We propose that dysregulation of ACE2 plays a critical role in the development of preeclampsia, fetal growth restriction, and COVID-19-associated pregnancy pathologies and suggest that human recombinant soluble ACE2 could be a novel therapeutic to treat and/or prevent these pregnancy complications.

Epigenetic processes during preeclampsia and effects on fetal development and chronic health.

Preeclampsia (PE), the leading cause of maternal and fetal morbidity and mortality, is associated with poor fetal growth, intrauterine growth restriction (IUGR) and low birth weight (LBW). Offspring of women who had PE are at increased risk for cardiovascular (CV) disease later in life. However, the exact etiology of PE is unknown. Moreover, there are no effective interventions to treat PE or alleviate IUGR and the developmental origins of chronic disease in the offspring. The placenta is critical to fetal growth and development. Epigenetic regulatory processes such as histone modifications, microRNAs and DNA methylation play an important role in placental development including contributions to the regulation of trophoblast invasion and remodeling of the spiral arteries. Epigenetic processes that lead to changes in placental gene expression in PE mediate downstream effects that contribute to the development of placenta dysfunction, a critical mediator in the onset of PE, impaired fetal growth and IUGR. Therefore, this review will focus on epigenetic processes that contribute to the pathogenesis of PE and IUGR. Understanding the epigenetic mechanisms that contribute to normal placental development and the initiating events in PE may lead to novel therapeutic targets in PE that improve fetal growth and mitigate increased CV risk in the offspring.

Time interval analysis of ductus venosus and cardiac cycles in relation with umbilical artery pH at birth in fetal growth restriction.

BACKGROUND: The aims of this study were to evaluate the time intervals of flow velocity waveforms (FVW) of ductus venosus (DV) and cardiac cycles, as well as the pulsatility index of DV-FVW (DV-PI), in correlation with umbilical artery (UA) pH at birth in fetal growth restriction (FGR) complicated with placental insufficiency. METHODS: Data were retrospectively retrieved from pregnancies complicated by FGR. FGR was defined as an estimated fetal weight below - 2.0 S.D. with an elevated UA-PI. Time interval assessments of DV-FVW were as follows: the duration of systolic wave was divided by the duration of diastolic wave and defined as DV-S/D. We also measured the following time intervals of ventricular inflow through tricuspid valve (TV) and mitral valve (MV): (iii), from the second peak of ventricular inflow caused by atrial contraction (A-wave) to the opening of atrio-ventricular valves and: (iv), from the opening of atrio-ventricular valves to the peak of A-wave. (iii)/(iv) was expressed as TV-S/D and MV-S/D, for TV and MV, respectively. The time interval data were transformed into z-scores. RESULTS: Thirty-one FGR fetuses were included in this study. Both DV-PI and DV-S/D showed significant correlation with UA-pH (r = - 0.677, p = < 0.001 and r = 0.489, p = 0.005 for DV-PI and z-score of DV-S/D, respectively) and more significances were observed in FGR ≤ 28 + 6 gestational weeks (r = - 0.819, p < 0.001 and r = 0.726, p = 0.005, for DV-PI and z-score of DV-S/D, respectively) than in FGR > 28 + 6 gestational weeks (r = - 0.634, p = 0.007 and r = 0.635, p = 0.020, for DV-PI and z-score of DV-S/D, respectively). On the other hand, TV-S/D and MV-S/D showed no significant correlation with UA-pH, although these z-scores indicated significant decreases compared with normal references. CONCLUSIONS: Time interval analysis of DV-FVW might be a valuable parameter, as well as DV-PI, for the antenatal prediction of fetal acidemia in the management of FGR fetuses.

Twin twin transfusion syndrome with and without selective fetal growth restriction: Predictors of donor demise.

OBJECTIVE: Evaluate survival in twin twin transfusion syndrome (TTTS) with and without selective fetal growth restriction (sFGR) after fetoscopic laser surgery (FLS). METHODS: Retrospective study of monochorionic diamniotic twins undergoing FLS. The cohort was classified as TTTS and TTTS with sFGR. Baseline, intra-operative and postoperative variables were analyzed. Mann-Whitney U, Pearson chi-square, Fisher's exact, t-test and receiver operating characteristic (ROC) curve analysis were performed. RESULTS: Four hundred and ninety-two pregnancies were included, 304 (61.78%) TTTS and 188 (38.22%) TTTS with sFGR. No difference in donor outcomes. TTTS group had higher donor estimated fetal weight (EFW%) percentile (19.7 ± 18.8 vs. 2.2 ± 2.1, p < 0.001). Significant predictors for demise at 30 days were 37% intertwin weight discordance (IWD) with donor EFW% < first (area under ROC curve [AUC] = 0.85, p = 0.001) or IWD >25% and intertwin umbilical artery pulsatility index discordance (DUAPI) ≥0.4 (AUC = 0.71, p = 0.001). CONCLUSION: Combination of IWD of 37% and donor EFW%

Endothelial Colony-Forming Cells Dysfunctions Are Associated with Arterial Hypertension in a Rat Model of Intrauterine Growth Restriction.

Infants born after intrauterine growth restriction (IUGR) are at risk of developing arterial hypertension at adulthood. The endothelium plays a major role in the pathogenesis of hypertension. Endothelial colony-forming cells (ECFCs), critical circulating components of the endothelium, are involved in vasculo-and angiogenesis and in endothelium repair. We previously described impaired functionality of ECFCs in cord blood of low-birth-weight newborns. However, whether early ECFC alterations persist thereafter and could be associated with hypertension in individuals born after IUGR remains unknown. A rat model of IUGR was induced by a maternal low-protein diet during gestation versus a control (CTRL) diet. In six-month-old offspring, only IUGR males have increased systolic blood pressure (tail-cuff plethysmography) and microvascular rarefaction (immunofluorescence). ECFCs isolated from bone marrow of IUGR versus CTRL males displayed a decreased proportion of CD31+ versus CD146+ staining on CD45- cells, CD34 expression (flow cytometry, immunofluorescence), reduced proliferation (BrdU incorporation), and an impaired capacity to form capillary-like structures (Matrigel test), associated with an impaired angiogenic profile (immunofluorescence). These dysfunctions were associated with oxidative stress (increased superoxide anion levels (fluorescent dye), decreased superoxide dismutase protein expression, increased DNA damage (immunofluorescence), and stress-induced premature senescence (SIPS; increased beta-galactosidase activity, increased p16INK4a, and decreased sirtuin-1 protein expression). This study demonstrated an impaired functionality of ECFCs at adulthood associated with arterial hypertension in individuals born after IUGR.

Peroxisome Deficiency Dysregulates Fatty Acid Oxidization and Exacerbates Lipotoxicity in ß Cells.

An adverse intrauterine environment impairs the development of pancreatic islets in the fetus and leads to insufficient ß cell mass and ß cell dysfunction. We previously reported that Pex14, a peroxin protein involved in the biogenesis and degradation of peroxisomes, is markedly reduced in the pancreas of an intrauterine growth restriction fetus and last into adulthood. Peroxisomes function in a wide range of metabolic processes including fatty acid oxidization, ROS detoxification, and anti-inflammatory responses. To elucidate the impact of downregulation of the Pex14 gene on ß cell, Pex14 was knocked down by siRNA in INS-1 cells. Pex14 knockdown disturbed peroxisomal biogenesis and dysregulated fatty acid metabolism and lipid storage capability, thereby increased ROS level and blunted insulin secretion. Moreover, Pex14 knockdown upregulated inflammation factors and regulators of endoplasmic reticulum stress. The lipotoxicity of fatty acid (including palmitic acid and linoleic acid) in ß cells was exacerbated by knockdown of Pex14, as indicated by H2O2 accumulation and increased programmed cell death. The present results demonstrate the vital role of Pex14 in maintaining normal peroxisome function and ß cell viability and highlight the importance of a functional peroxisomal metabolism for the detoxification of excess FAs in ß cells.

The relationship between placental characteristics and birthweight discordance in different types of selective intrauterine growth restriction in monochorionic diamniotic twins: A single-center 7 year cohort study.

OBJECTIVE: To clarify the relationships between placental characteristics and birthweight discordance in three types of selective intrauterine growth restriction (sIUGR) in monochorionic diamniotic twins. METHODS: A retrospective cohort study was conducted between april 2013 and april 2020. Associations between placental characteristics and birthweight discordance were evaluated through multiple linear regression analyses with two models for each sIUGR type. Model A was adjusted for gestational age, Model B additionally adjusted for the impact of placental characteristics interacted. RESULTS: In cases of type I sIUGR, birthweight discordance ratio was positively associated with placental territory discordance ratio [(ß = 0.181,95%CI(0.072,0.290), p < 0.05), (ß = 0.239,95%CI(0.125, 0.353), p < 0.05)] under both Model A and Model B. In-type II sIUGR [(ß = -0.012,95%CI(-0.020, -0.004), p < 0.05) (ß = -0.010,95%CI (-0.018, -0.002), p < 0.05)] and type III sIUGR [(ß = -0.011,95%CI (-0.021, -0.001), p < 0.05), (ß = -0.012,95%CI(-0.022, -0.003), p < 0.05)], birthweight discordance ratio was negatively associated with the total diameter of all the anastomoses as calculated with both Model A and Model B. CONCLUSION: Birthweight discordance is primarily related to placental territory discordance in type I sIUGR, whereas vascular anastomoses play important roles for growth-restricted fetal compensation in type II and III sIUGR.

A Systematic Review of Bisphenol A from Dietary and Non-Dietary Sources during Pregnancy and Its Possible Connection with Fetal Growth Restriction: Investigating Its Potential Effects and the Window of Fetal Vulnerability.

Bisphenol A (BPA), a ubiquitous endocrine-disrupting chemical (EDC), is increasingly hypothesized to be a factor contributing to changes in fetal growth velocity. BPA exposure may be environmental, occupational, and/or dietary, with canned foods and plastic bottles contributing significantly. Our systematic review aims to evaluate the current literature and to investigate the role of BPA in abnormal fetal growth patterns. A search was conducted in the PubMed and Cochrane databases. A total of 25 articles met the eligibility criteria and were included in this systematic review. Eleven of them failed to show a clear relationship between BPA and abnormal fetal growth. The majority of the remaining studies (9/14) found an inverse association of BPA with indicators of fetal growth, whereas three studies suggested increased fetal growth, and two studies produced contradictory findings. Of note, both of the studies that collected a sample (amniotic fluid) directly reflecting BPA concentration in the fetus during the first half of pregnancy revealed an inverse association with birth weight. In conclusion, there is mounting evidence that combined exposure to BPA from dietary and non-dietary sources during pregnancy may contribute to abnormal fetal growth; a tendency towards fetal growth restriction was shown, especially when exposure occurs during the first half.

In Utero Fetal Weight in Pigs Is Regulated by microRNAs and Their Target Genes.

Impaired skeletal muscle growth in utero can result in reduced birth weight and poor carcass quality in pigs. Recently, we showed the role of microRNAs (miRNAs) and their target genes in prenatal skeletal muscle development and pathogenesis of intrauterine growth restriction (IUGR). In this study, we performed an integrative miRNA-mRNA transcriptomic analysis in longissimus dorsi muscle (LDM) of pig fetuses at 63 days post conception (dpc) to identify miRNAs and genes correlated to fetal weight. We found 13 miRNAs in LDM significantly correlated to fetal weight, including miR-140, miR-186, miR-101, miR-15, miR-24, miR-29, miR-449, miR-27, miR-142, miR-99, miR-181, miR-199, and miR-210. The expression of these miRNAs decreased with an increase in fetal weight. We also identified 1315 genes significantly correlated to fetal weight at 63 dpc, of which 135 genes were negatively correlated as well as identified as potential targets of the above-listed 13 miRNAs. These miRNAs and their target genes enriched pathways and biological processes important for fetal growth, development, and metabolism. These results indicate that the transcriptomic profile of skeletal muscle can be used to predict fetal weight, and miRNAs correlated to fetal weight can serve as potential biomarkers of prenatal fetal health and growth.

Newer Insights Into Fetal Growth and Body Composition.

Based on epidemiological and experimental evidence, the origins of childhood obesity and early onset metabolic syndrome can be extended back to developmental processes during intrauterine life. It is necessary to actively investigate antecedent conditions that affect fetal growth by developing reliable measures to identify variations in fetal fat deposition and body composition. Recently, the resolution of ultrasonography has remarkably improved, which enables better tissue characterization and quantification of fetal fat accumulation. In addition, fetal fractional limb volume has been introduced as a novel measure to quantify fetal soft tissue volume, including fat mass and lean mass. Detecting extreme variations in fetal fat deposition may provide further insights into the origins of altered fetal body composition in pathophysiological conditions (i.e., fetal growth restriction or fetal macrosomia), which are predisposed to the metabolic syndrome in later life. Further studies are warranted to determine the maternal or placental factors that affect fetal fat deposition and body composition. Elucidating these factors may help develop clinical interventions for altered fetal growth and body composition, which could potentially lead to primary prevention of the future risk of metabolic dysfunction.

Reduction of In Vivo Placental Amino Acid Transport Precedes the Development of Intrauterine Growth Restriction in the Non-Human Primate.

Intrauterine growth restriction (IUGR) is associated with reduced placental amino acid transport (AAT). However, it remains to be established if changes in AAT contribute to restricted fetal growth. We hypothesized that reduced in vivo placental AAT precedes the development of IUGR in baboons with maternal nutrient restriction (MNR). Baboons were fed either a control (ad libitum) or MNR diet (70% of control diet) from gestational day (GD) 30. At GD 140, in vivo transplacental AA transport was measured by infusing nine (13)C- or (2)H-labeled essential amino acids (EAAs) as a bolus into the maternal circulation at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each EAA was measured. Microvillous plasma membrane (MVM) system A and system L transport activity were determined. Fetal and placental weights were not significantly different between MNR and control. In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly decreased for tryptophan in MNR. MVM system A and system L activity was markedly reduced in MNR. Reduction of in vivo placental amino acid transport precedes fetal growth restriction in the non-human primate, suggesting that reduced placental amino acid transfer may contribute to IUGR.

Placenta-specific Slc38a2/SNAT2 knockdown causes fetal growth restriction in mice.

Fetal growth restriction (FGR) is a complication of pregnancy that reduces birth weight, markedly increases infant mortality and morbidity and is associated with later-life cardiometabolic disease. No specific treatment is available for FGR. Placentas of human FGR infants have low abundance of sodium-coupled neutral amino acid transporter 2 (Slc38a2/SNAT2), which supplies the fetus with amino acids required for growth. We determined the mechanistic role of placental Slc38a2/SNAT2 deficiency in the development of restricted fetal growth, hypothesizing that placenta-specific Slc38a2 knockdown causes FGR in mice. Using lentiviral transduction of blastocysts with a small hairpin RNA (shRNA), we achieved 59% knockdown of placental Slc38a2, without altering fetal Slc38a2 expression. Placenta-specific Slc38a2 knockdown reduced near-term fetal and placental weight, fetal viability, trophoblast plasma membrane (TPM) SNAT2 protein abundance, and both absolute and weight-specific placental uptake of the amino acid transport System A tracer, 14C-methylaminoisobutyric acid (MeAIB). We also measured human placental SLC38A2 gene expression in a well-defined term clinical cohort and found that SLC38A2 expression was decreased in late-onset, but not early-onset FGR, compared with appropriate for gestational age (AGA) control placentas. The results demonstrate that low placental Slc38a2/SNAT2 causes FGR and could be a target for clinical therapies for late-onset FGR.