The CD94/NKG2A inhibitory receptor educates uterine NK cells to optimize pregnancy outcomes in humans and mice.

The conserved CD94/NKG2A inhibitory receptor is expressed by nearly all human and ∼50% of mouse uterine natural killer (uNK) cells. Binding human HLA-E and mouse Qa-1, NKG2A drives NK cell education, a process of unknown physiological importance influenced by HLA-B alleles. Here, we show that NKG2A genetic ablation in dams mated with wild-type males caused suboptimal maternal vascular responses in pregnancy, accompanied by perturbed placental gene expression, reduced fetal weight, greater rates of smaller fetuses with asymmetric growth, and abnormal brain development. These are features of the human syndrome pre-eclampsia. In a genome-wide association study of 7,219 pre-eclampsia cases, we found a 7% greater relative risk associated with the maternal HLA-B allele that does not favor NKG2A education. These results show that the maternal HLA-B→HLA-E→NKG2A pathway contributes to healthy pregnancy and may have repercussions on offspring health, thus establishing the physiological relevance for NK cell education. VIDEO ABSTRACT.

Inherent mosaicism and extensive mutation of human placentas.

Placentas can exhibit chromosomal aberrations that are absent from the fetus1. The basis of this genetic segregation, which is known as confined placental mosaicism, remains unknown. Here we investigated the phylogeny of human placental cells as reconstructed from somatic mutations, using whole-genome sequencing of 86 bulk placental samples (with a median weight of 28 mg) and of 106 microdissections of placental tissue. We found that every bulk placental sample represents a clonal expansion that is genetically distinct, and exhibits a genomic landscape akin to that of childhood cancer in terms of mutation burden and mutational imprints. To our knowledge, unlike any other healthy human tissue studied so far, the placental genomes often contained changes in copy number. We reconstructed phylogenetic relationships between tissues from the same pregnancy, which revealed that developmental bottlenecks genetically isolate placental tissues by separating trophectodermal lineages from lineages derived from the inner cell mass. Notably, there were some cases with full segregation-within a few cell divisions of the zygote-of placental lineages and lineages derived from the inner cell mass. Such early embryonic bottlenecks may enable the normalization of zygotic aneuploidy. We observed direct evidence for this in a case of mosaic trisomic rescue. Our findings reveal extensive mutagenesis in placental tissues and suggest that mosaicism is a typical feature of placental development.

Author Correction: Human placenta has no microbiome but can contain potential pathogens.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Human placenta has no microbiome but can contain potential pathogens.

We sought to determine whether pre-eclampsia, spontaneous preterm birth or the delivery of infants who are small for gestational age were associated with the presence of bacterial DNA in the human placenta. Here we show that there was no evidence for the presence of bacteria in the large majority of placental samples, from both complicated and uncomplicated pregnancies. Almost all signals were related either to the acquisition of bacteria during labour and delivery, or to contamination of laboratory reagents with bacterial DNA. The exception was Streptococcus agalactiae (group B Streptococcus), for which non-contaminant signals were detected in approximately 5% of samples collected before the onset of labour. We conclude that bacterial infection of the placenta is not a common cause of adverse pregnancy outcome and that the human placenta does not have a microbiome, but it does represent a potential site of perinatal acquisition of S. agalactiae, a major cause of neonatal sepsis.

Association between adverse pregnancy outcome and placental biomarkers in the first trimester: A prospective cohort study.

OBJECTIVE: To determine the inter-relationships between five first-trimester biomarkers (pregnancy associated plasma protein A [PAPP-A], alpha-fetoprotein [AFP], beta human chorionic gonadotrophin [beta-hCG], placenta growth factor [PlGF] and soluble fms-like tyrosine kinase receptor-1 [sFlt-1]) and a range of adverse pregnancy outcomes (APOs). DESIGN: Prospective cohort study of nulliparous singleton pregnancy. SETTING: Cambridge, UK. POPULATION OR SAMPLE: 4056 pregnancy outcome prediction study participants. METHODS: The biomarker concentrations were measured in maternal serum at ~12 weeks of gestation. Univariable analysis of APOs was performed using logistic regression. Multivariable analysis used best subsets logistic regression with cross-validation. MAIN OUTCOME MEASURES: Pre-eclampsia (PE), small for gestational age (SGA), including severe SGA (birthweight <3rd), fetal growth restriction (FGR), preterm birth (PTB, both induced and spontaneous [iPTB and sPTB, respectively]), pre-viable loss and stillbirth, plus combinations of outcomes. RESULTS: Lower values of PAPP-A, PlGF and sFlt-1 and higher values of AFP were associated with FGR (OR for 1 SD higher value 0.59 [95% CI 0.48-0.74], OR 0.56 [95% CI 0.44-0.70], OR 0.68 [95% CI 0.54-0.87] and OR 1.53 [95% CI 1.25-1.88]), severe SGA (OR 0.59 [95% CI 0.49-0.72], OR 0.71 [95% CI 0.57-0.87], OR 0.74 [95% CI 0.60-0.91] and OR 1.41 [95% CI 1.17-1.71]), sPTB (OR 0.61 [95% CI 0.50-0.73], OR 0.79 [95% CI 0.66-0.96], OR 0.57 [95% CI 0.47-0.70] and OR 1.41 [95% CI 1.18-1.67]) and iPTB (OR 0.72 [95% CI 0.57-0.91], OR 0.62 [95% CI 0.49-0.78], OR 0.71 [95% CI 0.56-0.90] and OR 1.44 [95% CI 1.16-1.78]), respectively. When combinations of biomarkers were assessed, PAPP-A and AFP were independently associated with severe SGA; PAPP-A alone with PE + PTB; PlGF alone with severe PE; PlGF, beta-hCG, AFP and PAPP-A with the combination of PE and SGA; AFP and sFlt-1 with sPTB; and AFP and PlGF with iPTB. CONCLUSIONS: Combinations of first-trimester placental biomarkers are associated with APOs. However, the patterns vary for different types of APO, indicating heterogeneity in the underlying pathophysiological pathways.

Association between antenatal diagnosis of late fetal growth restriction and educational outcomes in mid-childhood: A UK prospective cohort study with long-term data linkage study.

BACKGROUND: Fetal growth restriction (FGR) is associated with a suboptimal intrauterine environment, which may adversely impact fetal neurodevelopment. However, analysing neurodevelopmental outcomes by observed birthweight fails to differentiate between true FGR and constitutionally small infants and cannot account for iatrogenic intervention. This study aimed to determine the relationship between antenatal FGR and mid-childhood (age 5 to 7 years) educational outcomes. METHODS AND FINDINGS: The Pregnancy Outcome Prediction Study (2008-2012) was a prospective birth cohort conducted in a single maternity hospital in Cambridge, United Kingdom. Clinicians were blinded to the antenatal diagnosis of FGR. FGR was defined as estimated fetal weight (EFW) <10th percentile at approximately 36 weeks of gestation, plus one or more indicators of placental dysfunction, including ultrasonic markers and maternal serum levels of placental biomarkers. A total of 2,754 children delivered at term were divided into 4 groups: FGR, appropriate-for-gestational age (AGA) with markers of placental dysfunction, healthy small-for-gestational age (SGA), and healthy AGA (referent). Educational outcomes (assessed at 5 to 7 years using UK national standards) were assessed with respect to FGR status using regression models adjusted for relevant covariates, including maternal, pregnancy, and socioeconomic factors. Compared to healthy AGA (N = 1,429), children with FGR (N = 250) were at higher risk of "below national standard" educational performance at 6 years (18% versus 11%; aOR 1.68; 95% CI 1.12 to 2.48, p = 0.01). By age 7, children with FGR were more likely to perform below standard in reading (21% versus 15%; aOR 1.46; 95% CI 0.99 to 2.13, p = 0.05), writing (28% versus 23%; aOR 1.46; 95% CI 1.02 to 2.07, p = 0.04), and mathematics (24% versus 16%; aOR 1.49; 95% CI 1.02 to 2.15, p = 0.03). This was consistent whether FGR was defined by ultrasound or biochemical markers. The educational attainment of healthy SGA children (N = 126) was comparable to healthy AGA, although this comparison may be underpowered. Our study design relied on linkage of routinely collected educational data according to nationally standardised metrics; this design allowed a high percentage of eligible participants to be included in the analysis (75%) but excludes those children educated outside of government-funded schools in the UK. Our focus on pragmatic and validated measures of educational attainment does not exclude more subtle effects of the intrauterine environment on specific aspects of neurodevelopment. CONCLUSIONS: Compared to children with normal fetal growth and no markers of placental dysfunction, FGR is associated with poorer educational attainment in mid-childhood.

Maternal serum levels of soluble fms-like tyrosine kinase-1 and placental growth factor at 20 and 28 weeks of gestational age and the risk of spontaneous preterm birth.

BACKGROUND: Spontaneous preterm birth is the endpoint of multiple different pathophysiological pathways. Fetal growth restriction, assessed by serial ultrasonic fetal biometry, has been shown to predict both preterm and early-term spontaneous labor. The soluble fms-like tyrosine kinase-1 to placental growth factor ratio is predictive of early-term spontaneous labor, but its association with spontaneous preterm birth is unclear. OBJECTIVE: This study aimed to determine whether maternal serum levels of soluble fms-like tyrosine kinase-1, placental growth factor, and the soluble fms-like tyrosine kinase-1: placental growth factor ratio at 20 and 28 weeks' gestation, and the rate of change in these biomarkers between 20 and 28 weeks were predictive of risk of spontaneous preterm birth. STUDY DESIGN: The biomarkers were measured in maternal serum at 20- and 28-weeks' gestation in women recruited to a prospective cohort of unselected nulliparous women as part of the Pregnancy Outcome Prediction study in Cambridge, United Kingdom. The risk of spontaneous preterm birth was assessed using Cox regression and competing-risks regression. Associations from Cox regression were quantified by the adjusted hazard ratio for a 1 standard deviation higher level of a given biomarker or a 1 standard deviation increase in the marker between 20 and 28 weeks' gestation. A previously identified risk factor, slow femur length growth, was used as an additional predictor of spontaneous preterm birth for the purpose of risk stratification. RESULTS: Of the 3763 participants in the analysis, 95 (2.5%) had spontaneous preterm birth and 54 (1.4%) had medically indicated preterm birth. At 20 weeks' gestation, higher levels of soluble fms-like tyrosine kinase-1 and the soluble fms-like tyrosine kinase-1:placental growth factor ratio were associated with reduced risk of spontaneous preterm birth (adjusted hazard ratio [95% confidence interval], 0.75 [0.61-0.92]; P=.006 and 0.71 [0.59-0.87]; P=.0009, respectively). At 28 weeks' gestation, there was no association between either soluble fms-like tyrosine kinase-1 or placental growth factor and the risk of spontaneous preterm birth, but there was a U-shaped relation with the soluble fms-like tyrosine kinase-1:placental growth factor ratio. However, when the biomarkers were quantified as the rate of increase between 20 and 28 weeks' gestation, there were strong positive associations between spontaneous preterm birth and rate of increase in soluble fms-like tyrosine kinase-1 (1.36 [1.13-1.63]; P=.001) and the soluble fms-like tyrosine kinase-1:placental growth factor ratio (1.50 [1.30-1.73]; P<.0001), and a strong negative association with the rate of increase in placental growth factor (0.71 [0.61-0.82]; P<.0001). Women who were in the highest decile of increase in the soluble fms-like tyrosine kinase-1:placental growth factor ratio and the lowest decile of femur length growth between 20 and 28 weeks' gestation had approximately 9-fold risk of spontaneous preterm birth (9.27 [4.21-20.37]; P<.0001). Competing-risks regression yielded similar results. CONCLUSION: Changing levels of soluble fms-like tyrosine kinase-1 and placental growth factor are indicative of placental dysfunction and are strongly associated with the risk of spontaneous preterm birth, especially when combined with slower fetal femur length growth.

Maternal high body mass index, but not gestational diabetes, is associated with poorer educational attainment in mid-childhood.

BACKGROUND: Previous studies suggest that gestational diabetes mellitus is associated with poorer cognitive outcomes in children. However, confounding factors, especially maternal body mass index, have been poorly accounted for. OBJECTIVE: This study aimed to examine the independent associations between maternal body mass index, gestational diabetes mellitus status, and educational outcomes. STUDY DESIGN: Antenatal data from a prospective birth cohort (Pregnancy Outcome Prediction Study, 2008-2012, Cambridge, United Kingdom) were linked to mid-childhood educational outcomes (Department for Education, United Kingdom). A total of 3249 children born at term were stratified by maternal gestational diabetes mellitus status and body mass index at booking (<25 vs ≥25 kg/m2). Regression models adjusted for relevant maternal, child, and socioeconomic factors were used to determine associations with academic outcomes at ages of 5 to 7 years. RESULTS: No differences in educational attainment were found between children exposed to gestational diabetes mellitus and nonexposed children. Neither maternal glucose levels measured at 11 to 14 or 24 to 28 weeks, nor acceleration of the fetal abdominal circumference growth velocity were related to educational attainment at ages of 5 to 7 years. Children of mothers with booking body mass index ≥25 kg/m2 (vs <25 kg/m2) were ∼50% more likely to not meet expected educational standards regardless of gestational diabetes mellitus status (age 5: adjusted odds ratio, 1.44; 95% confidence interval, 1.19-1.74; P<.001; age 6: adjusted odds ratio, 1.61; 95% confidence interval, 1.28-2.02; P<.001). The association between maternal body mass index and offspring educational attainment is dose-dependent and robust to stratification by gestational diabetes mellitus status and adjustment for socioeconomic factors. CONCLUSION: Mid-childhood educational attainment is not associated with maternal glucose status. This may provide important reassurance for pregnant women and clinicians. However, maternal body mass index is associated with lower childhood educational attainment and may be modifiable with intervention before or during pregnancy.

Prediction of spontaneous preterm birth using supervised machine learning on metabolomic data: A case-cohort study.

OBJECTIVES: To identify and internally validate metabolites predictive of spontaneous preterm birth (sPTB) using multiple machine learning methods and sequential maternal serum samples, and to predict spontaneous early term birth (sETB) using these metabolites. DESIGN: Case-cohort design within a prospective cohort study. SETTING: Cambridge, UK. POPULATION OR SAMPLE: A total of 399 Pregnancy Outcome Prediction study participants, including 98 cases of sPTB. METHODS: An untargeted metabolomic analysis of maternal serum samples at 12, 20, 28 and 36 weeks of gestation was performed. We applied six supervised machine learning methods and a weighted Cox model to measurements at 28 weeks of gestation and sPTB, followed by feature selection. We used logistic regression with elastic net penalty, followed by best subset selection, to reduce the number of predictive metabolites further. We applied coefficients from the chosen models to measurements from different gestational ages to predict sPTB and sETB. MAIN OUTCOME MEASURES: sPTB and sETB. RESULTS: We identified 47 metabolites, mostly lipids, as important predictors of sPTB by two or more methods and 22 were identified by three or more methods. The best 4-predictor model had an optimism-corrected area under the receiver operating characteristics curve (AUC) of 0.703 at 28 weeks of gestation. The model also predicted sPTB in 12-week samples (0.606, 95% CI 0.544-0.667) and 20-week samples (0.657, 95% CI 0.597-0.717) and it predicted sETB in 36-week samples (0.727, 95% CI 0.606-0.849). A lysolipid, 1-palmitoleoyl-GPE (16:1)*, was the strongest predictor of sPTB at 12 weeks of gestation (0.609, 95% CI 0.548-0.670), 20 weeks (0.630, 95% CI 0.569-0.690) and 28 weeks (0.660, 95% CI 0.599-0.722), and of sETB at 36 weeks (0.739, 95% CI 0.618-0.860). CONCLUSIONS: We identified and internally validated maternal serum metabolites predictive of sPTB. A lysolipid, 1-palmitoleoyl-GPE (16:1)*, is a novel predictor of sPTB and sETB. Further validation in external populations is required.

Circulating maternal placental growth factor responses to low-molecular-weight heparin in pregnant patients at risk of placental dysfunction.

BACKGROUND: Patients at high risk of severe preeclampsia and fetal growth restriction have low circulating levels of placental growth factor and features of maternal vascular malperfusion placental pathology at delivery. Multimodal screening and commencement of aspirin prophylaxis at 11 to 13 weeks' gestation markedly reduces the risk of preterm delivery with preeclampsia. However, the additional role of low-molecular-weight heparin and mechanisms of action remain uncertain. Because low-molecular-weight heparin augments the production and release of placental growth factor in vitro by both placental villi and vascular endothelium, it may be effective to suppress the risk of severe preeclampsia in a niche group of high-risk patients with low circulating placental growth factor in the early second trimester. OBJECTIVE: This study aimed to define a gestational age-specific reference range for placental growth factor and to test the hypothesis that prophylactic low-molecular-weight heparin administered in the early second trimester may restore deficient circulating placental growth factor levels and thereby prolong pregnancy. STUDY DESIGN: Centile curves for circulating placental growth factor levels from 12 to 36 weeks' gestation were derived using quantile regression of combined data from a published cohort of 4207 unselected nulliparous patients in Cambridge, United Kingdom, at 4 sampling time points (12, 20, 28, and 36 weeks' gestation) and the White majority (n=531) of a healthy nulliparous cohort in Toronto, Canada, at 16 weeks' gestation using the same test platform. Within a specialty high-risk clinic in Toronto, a niche group of 7 patients with a circulating placental growth factor at the <10th centile in the early second trimester received daily prophylactic low-molecular-weight heparin (enoxaparin; 40 mg subcutaneously) and were followed up until delivery (group 1). Their baseline characteristics, delivery details, and placental pathologies were compared with 5 similar patients who did not receive low-molecular-weight heparin during the observation period (group 2) and further with 21 patients who delivered with severe preeclampsia (group 3) in the same institution. RESULTS: A gestational age-specific reference range for placental growth factor levels at weekly intervals between 12 and 36 weeks was established for White women with singleton pregnancies. Within group 1, 5 of 7 patients demonstrated a sustained increase in circulating placental growth factor levels, whereas placental growth factor levels did not increase in group 2 or group 3 patients who did not receive low-molecular-weight heparin. Group 1 patients receiving low-molecular-weight heparin therapy exhibited a later gestation at delivery, relative to groups 2 and 3 (36 weeks [33-37] vs 23 weeks [22-26] and 28 weeks [27-31], respectively), and consequently had higher birthweights (1.93 kg [1.1-2.7] vs 0.32 kg [0.19-0.39] and 0.73 kg [0.52-1.03], respectively). The incidence of stillbirth was lowest in group 1 (14% [1 of 7]), relative to groups 2 and 3 (80% [4 of 5] and 29% [6 of 21], respectively). Maternal vascular malperfusion was the most common placental pathology found in association with abnormal uterine artery Doppler. CONCLUSION: In patients at high risk of a serious adverse pregnancy outcome owing to placental disease, the addition of low-molecular-weight heparin to aspirin prophylaxis in the early second trimester may restore deficient circulating placental growth factor to mediate an improved perinatal outcome. These data support the implementation of a multicenter pilot randomized control trial where patients are recruited primarily based on the assessment of placental function in the early second trimester.

Comparison of estimated fetal weight percentiles near term for predicting extremes of birthweight percentile.

BACKGROUND: The INTERGROWTH-21st estimated fetal weight percentiles are recommended for predicting extremes of birthweight percentile, although evidence for their superiority over the widely employed Hadlock method is lacking. OBJECTIVE: This study aimed to compare the ability of estimated fetal weight percentiles calculated using the Hadlock method and the INTERGROWTH-21st method to predict extremes of birthweight percentile. STUDY DESIGN: A prospective cohort study of blinded serial ultrasonography in nulliparous women with a singleton pregnancy, The Pregnancy Outcome Prediction study was conducted in Cambridge, United Kingdom. The study participants who had a research estimated fetal weight performed at 36 weeks' gestation were eligible for the analysis. Estimated fetal weight percentiles for gestational age calculated using (1) the Hadlock method or (2) the INTERGROWTH-21st method were used as exposures. Birthweight percentiles of <10th (small for gestational age) and >90th (large for gestational age) for gestational age and fetal sex using the United Kingdom 1990 reference or the INTERGROWTH-21st birthweight reference were analyzed as outcomes using receiver operating characteristic curve analysis. Screening statistics from 2×2 tables were calculated for dichotomized exposures and each outcome. RESULTS: The Hadlock estimated fetal weight percentile performed better than the INTERGROWTH-21st estimated fetal weight percentile at discriminating both small for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.85; 95% confidence intervals, 0.85-0.89 vs 0.83-0.87, respectively; P<.0001) and large for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.86; 95% confidence intervals, 0.85-0.90 vs 0.83-0.89, respectively; P=.005). When the estimated fetal weight percentiles were dichotomized and screen positive was defined at 90% specificity, the sensitivity for the Hadlock vs the INTERGROWTH-21st method was 58.6% vs 52.3%, respectively, for small for gestational age, and 71.0% vs 60.9%, respectively, for birthweight at less than the third percentile (United Kingdom 1990 reference). The results were similar when the birthweight percentile was defined using the INTERGROWTH-21st birthweight reference, when the estimated fetal weight was calculated without the inclusion of head measurements, or when the women who had clinically indicated scans and women who had their research scan result were excluded. CONCLUSION: Replacing the Hadlock method by the INTERGROWTH-21st method may lead to less effective screening for extremes of birthweight percentile.

Slowing of fetal growth and elevated maternal serum sFLT1:PlGF are associated with early term spontaneous labor.

BACKGROUND: The physiological control of human parturition at term is unknown. OBJECTIVE: This study aimed to test the hypothesis that slowing of fetal growth or elevated maternal serum levels of markers of placental hypoxia in late gestation will be associated with earlier term labor. STUDY DESIGN: We observed 2208 women having first births and performed serial blinded ultrasonography and immunoassay of soluble fms-like tyrosine kinase-1 and placenta growth factor. We estimated the probability of spontaneous delivery from 37 weeks of gestational age concerning (1) fetal growth between 20 and 36 weeks of gestational age and (2) the maternal serum soluble fms-like tyrosine kinase-1-to-placenta growth factor ratio measured at approximately 36 weeks of gestational age. Data were analyzed using logistic regression and Cox regression. RESULTS: Fetal size at 36 weeks of gestational age was not independently associated with the timing of delivery at term. However, there was an inverse relationship between fetal growth between 20 weeks of gestational age and 36 weeks of gestational age and the probability of spontaneous labor at 37 to 38 weeks' gestation (hazard ratio [95% confidence interval] for a 50 percentile increase in abdominal circumference growth velocity, 0.60 [0.47-0.78]; P=.0001). This association was weaker at 39 to 40 weeks' gestation (0.83 [0.74-0.93]; P=.0013), and there was no association at ≥41 weeks' gestation. Very similar associations were observed for estimated fetal weight growth velocity. There was a positive relationship between soluble fms-like tyrosine kinase-1-to-placenta growth factor ratio and the probability of spontaneous labor at 37 to 38 weeks' gestation (hazard ratio [95% confidence interval] for a 50 percentile increase in soluble fms-like tyrosine kinase-1-to-placenta growth factor ratio, 3.05 [2.32-4.02]; P<.0001). This association was weaker at 39 to 40 weeks' gestation (1.46 [1.30-1.63]; P<.0001), and there was no association at ≥41 weeks' gestation. Adjustment for maternal characteristics was without material effect on any of these associations. CONCLUSION: Slowing of fetal growth and biomarkers of placental insufficiency were associated with an increased probability of early onset of spontaneous term labor. We speculated that progressive placental insufficiency may be a physiological phenomenon that occurs with advancing gestational age near and at term and promotes the initiation of labor.

Abnormal placental CD8+ T-cell infiltration is a feature of fetal growth restriction and pre-eclampsia.

KEY POINTS: Placental pathological abnormalities are more frequently observed in complicated pregnancies than in healthy pregnancies. Infiltration of CD8+ T-cells into the placental villous tissue occurred in both fetal growth restriction and pre-eclampsia, whereas CD79α+ B-cell infiltration was only apparent with reduced fetal growth. Vascularization, fibrin depositions, macrophage and neutrophil infiltration in the placenta did not differ between healthy and complicated pregnancies. ABSTRACT: Fetal growth restriction (FGR) and pre-eclampsia are severe, adverse pregnancy outcomes. Alterations in placental histology are frequently reported in these pregnancy complications and are often based upon scoring by pathologists. However, many alterations are also observed in placenta from uncomplicated pregnancies. Moreover, knowledge of disease state may bias assessment. We sought to perform an objective comparison of placental microscopic appearance in normal and complicated pregnancies. Placental villous tissue (n = 823) and edge biopsies (n = 488) from 871 individual, singleton pregnancies were collected after delivery. Cases of small-for-gestational age (SGA) or pre-eclampsia were matched with healthy controls. A subset of the SGA cases displayed signs of FGR. Cases of preterm delivery were also included. Tissue sections were stained with haematoxylin and eosin or antibodies for CD8, CD14, CD31, CD79α and elastase. Images were scored by two experienced pathologists for pathological features or analysed by image analysis and stereology. Analyses were performed blind to case-control status and gestational age. Volume fraction of T-cells increased in placentas from pregnancies complicated by pre-eclampsia (adjusted odds ratio (aOR) 1.46, 95% CI: 1.12-1.90) and FGR (aOR 1.64, 95% CI: 1.11-2.43), whereas B-cells only increased in FGR (aOR 1.65, 95% CI: 1.05-2.60). Pathological abnormalities in villous tissue were reported in 21.4% (88/411) of complicated pregnancies and 14.3% (52/363) of controls (OR 1.62, 95% CI: 1.12-2.37). There were no differences in the fractions of endothelial cells, fibrin deposition, macrophages and neutrophils when comparing normal and complicated pregnancies. In conclusion, FGR and pre-eclampsia are associated with T-cell infiltration of the placenta and placental pathological abnormalities.

Universal third-trimester ultrasonic screening using fetal macrosomia in the prediction of adverse perinatal outcome: A systematic review and meta-analysis of diagnostic test accuracy.

BACKGROUND: The effectiveness of screening for macrosomia is not well established. One of the critical elements of an effective screening program is the diagnostic accuracy of a test at predicting the condition. The objective of this study is to investigate the diagnostic effectiveness of universal ultrasonic fetal biometry in predicting the delivery of a macrosomic infant, shoulder dystocia, and associated neonatal morbidity in low- and mixed-risk populations. METHODS AND FINDINGS: We conducted a predefined literature search in Medline, Excerpta Medica database (EMBASE), the Cochrane library and ClinicalTrials.gov from inception to May 2020. No language restrictions were applied. We included studies where the ultrasound was performed as part of universal screening and those that included low- and mixed-risk pregnancies and excluded studies confined to high risk pregnancies. We used the estimated fetal weight (EFW) (multiple formulas and thresholds) and the abdominal circumference (AC) to define suspected large for gestational age (LGA). Adverse perinatal outcomes included macrosomia (multiple thresholds), shoulder dystocia, and other markers of neonatal morbidity. The risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Meta-analysis was carried out using the hierarchical summary receiver operating characteristic (ROC) and the bivariate logit-normal (Reitsma) models. We identified 41 studies that met our inclusion criteria involving 112,034 patients in total. These included 11 prospective cohort studies (N = 9986), one randomized controlled trial (RCT) (N = 367), and 29 retrospective cohort studies (N = 101,681). The quality of the studies was variable, and only three studies blinded the ultrasound findings to the clinicians. Both EFW >4,000 g (or 90th centile for the gestational age) and AC >36 cm (or 90th centile) had >50% sensitivity for predicting macrosomia (birthweight above 4,000 g or 90th centile) at birth with positive likelihood ratios (LRs) of 8.74 (95% confidence interval [CI] 6.84-11.17) and 7.56 (95% CI 5.85-9.77), respectively. There was significant heterogeneity at predicting macrosomia, which could reflect the different study designs, the characteristics of the included populations, and differences in the formulas used. An EFW >4,000 g (or 90th centile) had 22% sensitivity at predicting shoulder dystocia with a positive likelihood ratio of 2.12 (95% CI 1.34-3.35). There was insufficient data to analyze other markers of neonatal morbidity. CONCLUSIONS: In this study, we found that suspected LGA is strongly predictive of the risk of delivering a large infant in low- and mixed-risk populations. However, it is only weakly (albeit statistically significantly) predictive of the risk of shoulder dystocia. There was insufficient data to analyze other markers of neonatal morbidity.

Independent influences of maternal obesity and fetal sex on maternal cardiovascular adaptation to pregnancy: a prospective cohort study.

BACKGROUND/OBJECTIVES: Successful pregnancy requires the de novo creation of low-resistance utero-placental and feto-placental circulations and incomplete remodeling of this vasculature can lead to maternal or fetal compromise. Maternal BMI and fetal sex are known to influence vascular compliance and placental development, but it is unknown if these are independent or synergistic effects. Here we aim to investigate the impact of maternal obesity, fetal sex, and any interaction thereof on maternal cardiovascular adaptation to pregnancy, by assessing the physiological drop of uterine artery doppler pulsatility (UtA-PI) and umbilical artery doppler pulsatility index (UA-PI) over gestation. SUBJECTS/METHODS: Nulliparous women with a singleton pregnancy participating in a prospective cohort study (n = 4212) underwent serial UtA-PI and UA-PI measurements at 20-, 28- and 36-weeks gestation. Linear mixed regression models were employed to investigate the influence of maternal BMI, fetal sex and interactions thereof on the magnitude of change in UtA-PI and UA-PI. RESULTS: Throughout gestation, UtA-PI was higher for male fetuses and UA-PI was higher for female fetuses. The physiological drop of UtA-PI was significantly smaller in overweight (change -24.3% [95%CI -22.3, -26.2]) and obese women (change -21.3% [-18.3, -24.3]), compared to normal-weight women (change -25.7% [-24.3, -27.0]) but did not differ by fetal sex. The physiological drop in UA-PI was greater for female than male fetuses (-32.5% [-31.5, -33.5] vs. -30.7% [-29.8, -31.7]) but did not differ by maternal BMI. No interactions between maternal BMI and fetal sex were found. CONCLUSIONS: Maternal cardiovascular adaptation to pregnancy is independently associated with maternal BMI and fetal sex. Our results imply sexual dimorphism in both maternal cardiovascular adaptation and feto-placental resistance.

Screening for breech presentation using universal late-pregnancy ultrasonography: A prospective cohort study and cost effectiveness analysis.

BACKGROUND: Despite the relative ease with which breech presentation can be identified through ultrasound screening, the assessment of foetal presentation at term is often based on clinical examination only. Due to limitations in this approach, many women present in labour with an undiagnosed breech presentation, with increased risk of foetal morbidity and mortality. This study sought to determine the cost effectiveness of universal ultrasound scanning for breech presentation near term (36 weeks of gestational age [wkGA]) in nulliparous women. METHODS AND FINDINGS: The Pregnancy Outcome Prediction (POP) study was a prospective cohort study between January 14, 2008 and July 31, 2012, including 3,879 nulliparous women who attended for a research screening ultrasound examination at 36 wkGA. Foetal presentation was assessed and compared for the groups with and without a clinically indicated ultrasound. Where breech presentation was detected, an external cephalic version (ECV) was routinely offered. If the ECV was unsuccessful or not performed, the women were offered either planned cesarean section at 39 weeks or attempted vaginal breech delivery. To compare the likelihood of different mode of deliveries and associated long-term health outcomes for universal ultrasound to current practice, a probabilistic economic simulation model was constructed. Parameter values were obtained from the POP study, and costs were mainly obtained from the English National Health Service (NHS). One hundred seventy-nine out of 3,879 women (4.6%) were diagnosed with breech presentation at 36 weeks. For most women (96), there had been no prior suspicion of noncephalic presentation. ECV was attempted for 84 (46.9%) women and was successful in 12 (success rate: 14.3%). Overall, 19 of the 179 women delivered vaginally (10.6%), 110 delivered by elective cesarean section (ELCS) (61.5%) and 50 delivered by emergency cesarean section (EMCS) (27.9%). There were no women with undiagnosed breech presentation in labour in the entire cohort. On average, 40 scans were needed per detection of a previously undiagnosed breech presentation. The economic analysis indicated that, compared to current practice, universal late-pregnancy ultrasound would identify around 14,826 otherwise undiagnosed breech presentations across England annually. It would also reduce EMCS and vaginal breech deliveries by 0.7 and 1.0 percentage points, respectively: around 4,196 and 6,061 deliveries across England annually. Universal ultrasound would also prevent 7.89 neonatal mortalities annually. The strategy would be cost effective if foetal presentation could be assessed for £19.80 or less per woman. Limitations to this study included that foetal presentation was revealed to all women and that the health economic analysis may be altered by parity. CONCLUSIONS: According to our estimates, universal late pregnancy ultrasound in nulliparous women (1) would virtually eliminate undiagnosed breech presentation, (2) would be expected to reduce foetal mortality in breech presentation, and (3) would be cost effective if foetal presentation could be assessed for less than £19.80 per woman.

The effect of customization and use of a fetal growth standard on the association between birthweight percentile and adverse perinatal outcome.

BACKGROUND: It has been proposed that correction of offspring weight percentiles (customization) might improve the prediction of adverse pregnancy outcome; however, the approach is not accepted universally. A complication in the interpretation of the data is that the main method for calculation of customized percentiles uses a fetal growth standard, and multiple analyses have compared the results with birthweight-based standards. OBJECTIVES: First, we aimed to determine whether women who deliver small-for-gestational-age infants using a customized standard differed from other women. Second, we aimed to compare the association between birthweight percentile and adverse outcome using 3 different methods for percentile calculation: (1) a noncustomized actual birthweight standard, (2) a noncustomized fetal growth standard, and (3) a fully customized fetal growth standard. STUDY DESIGN: We analyzed data from the Pregnancy Outcome Prediction study, a prospective cohort study of nulliparous women who delivered in Cambridge, UK, between 2008 and 2013. We used a composite adverse outcome, namely, perinatal morbidity or preeclampsia. Receiver operating characteristic curve analysis was used to compare the 3 methods of calculating birthweight percentiles in relation to the composite adverse outcome. RESULTS: We confirmed previous observations that delivering an infant who was small for gestational age (<10th percentile) with the use of a fully customized fetal growth standard but who was appropriate for gestational age with the use of a noncustomized actual birthweight standard was associated with higher rates of adverse outcomes. However, we also observed that the mothers of these infants were 3-4 times more likely to be obese and to deliver preterm. When we compared the risk of adverse outcome from logistic regression models that were fitted to the birthweight percentiles that were derived by each of the 3 predefined methods, the areas under the receiver operating characteristic curves were similar for all 3 methods: 0.56 (95% confidence interval, 0.54-0.59) fully customized, 0.56 (95% confidence interval, 0.53-0.59) noncustomized fetal weight standard, and 0.55 (95% confidence interval, 0.53-0.58) noncustomized actual birthweight standard. When we classified the top 5% of predicted risk as high risk, the methods that used a fetal growth standard showed attenuation after adjustment for gestational age, whereas the birthweight standard did not. Further adjustment for the maternal characteristics, which included weight, attenuated the association with the customized standard, but not the other 2 methods. The associations after full adjustment were similar when we compared the 3 approaches. CONCLUSION: The independent association between birthweight percentile and adverse outcome was similar when we compared actual birthweight standards and fetal growth standards and compared customized and noncustomized standards. Use of fetal weight standards and customized percentiles for maternal characteristics could lead to stronger associations with adverse outcome through confounding by preterm birth and maternal obesity.

Screening for fetal growth restriction using fetal biometry combined with maternal biomarkers.

Fetal growth restriction is a major determinant of perinatal morbidity and mortality. Screening for fetal growth restriction is a key element of prenatal care but it is recognized to be problematic. Screening using clinical risk assessment and targeting ultrasound to high-risk women is the standard of care in the United States and United Kingdom, but the approach is known to have low sensitivity. Systematic reviews of randomized controlled trials do not demonstrate any benefit from universal ultrasound screening for fetal growth restriction in the third trimester, but the evidence base is not strong. Implementation of universal ultrasound screening in low-risk women in France failed to reduce the risk of complications among small-for-gestational-age infants but did appear to cause iatrogenic harm to false positives. One strategy to making progress is to improve screening by developing more sensitive and specific tests with the key goal of differentiating between healthy small fetuses and those that are small through fetal growth restriction. As abnormal placentation is thought to be the major cause of fetal growth restriction, one approach is to combine fetal biometry with an indicator of placental dysfunction. In the past, these indicators were generally ultrasonic measurements, such as Doppler flow velocimetry of the uteroplacental circulation. However, another promising approach is to combine ultrasonic suspicion of small-for-gestational-age infant with a blood test indicating placental dysfunction. Thus far, much of the research on maternal serum biomarkers for fetal growth restriction has involved the secondary analysis of tests performed for other indications, such as fetal aneuploidies. An exemplar of this is pregnancy-associated plasma protein A. This blood test is performed primarily to assess the risk of Down syndrome, but women with low first-trimester levels are now serially scanned in later pregnancy due to associations with placental causes of stillbirth, including fetal growth restriction. The development of "omic" technologies presents a huge opportunity to identify novel biomarkers for fetal growth restriction. The hope is that when such markers are measured alongside ultrasonic fetal biometry, the combination would have strong predictive power for fetal growth restriction and its related complications. However, a series of important methodological considerations in assessing the diagnostic effectiveness of new tests will have to be addressed. The challenge thereafter will be to identify novel disease-modifying interventions, which are the essential partner to an effective screening test to achieve clinically effective population-based screening.