External validation of prognostic models to predict stillbirth using International Prediction of Pregnancy Complications (IPPIC) Network database: individual participant data meta-analysis.

OBJECTIVE: Stillbirth is a potentially preventable complication of pregnancy. Identifying women at high risk of stillbirth can guide decisions on the need for closer surveillance and timing of delivery in order to prevent fetal death. Prognostic models have been developed to predict the risk of stillbirth, but none has yet been validated externally. In this study, we externally validated published prediction models for stillbirth using individual participant data (IPD) meta-analysis to assess their predictive performance. METHODS: MEDLINE, EMBASE, DH-DATA and AMED databases were searched from inception to December 2020 to identify studies reporting stillbirth prediction models. Studies that developed or updated prediction models for stillbirth for use at any time during pregnancy were included. IPD from cohorts within the International Prediction of Pregnancy Complications (IPPIC) Network were used to validate externally the identified prediction models whose individual variables were available in the IPD. The risk of bias of the models and cohorts was assessed using the Prediction study Risk Of Bias ASsessment Tool (PROBAST). The discriminative performance of the models was evaluated using the C-statistic, and calibration was assessed using calibration plots, calibration slope and calibration-in-the-large. Performance measures were estimated separately in each cohort, as well as summarized across cohorts using random-effects meta-analysis. Clinical utility was assessed using net benefit. RESULTS: Seventeen studies reporting the development of 40 prognostic models for stillbirth were identified. None of the models had been previously validated externally, and the full model equation was reported for only one-fifth (20%, 8/40) of the models. External validation was possible for three of these models, using IPD from 19 cohorts (491 201 pregnant women) within the IPPIC Network database. Based on evaluation of the model development studies, all three models had an overall high risk of bias, according to PROBAST. In the IPD meta-analysis, the models had summary C-statistics ranging from 0.53 to 0.65 and summary calibration slopes ranging from 0.40 to 0.88, with risk predictions that were generally too extreme compared with the observed risks. The models had little to no clinical utility, as assessed by net benefit. However, there remained uncertainty in the performance of some models due to small available sample sizes. CONCLUSIONS: The three validated stillbirth prediction models showed generally poor and uncertain predictive performance in new data, with limited evidence to support their clinical application. The findings suggest methodological shortcomings in their development, including overfitting. Further research is needed to further validate these and other models, identify stronger prognostic factors and develop more robust prediction models. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Breech presentation is associated with lower adolescent tibial bone strength.

We compared bone outcomes in adolescents with breech and cephalic presentation. Tibia bone mineral content, density, periosteal circumference, and cross-sectional moment of inertia were lower in breech presentation, and females with breech presentation had lower hip CSA. These findings suggest that prenatal loading may exert long-lasting influences on skeletal development. INTRODUCTION: Breech position during pregnancy is associated with reduced range of fetal movement, and with lower limb joint stresses. Breech presentation at birth is associated with lower neonatal bone mineral content (BMC) and area, but it is unknown whether these associations persist into later life. METHODS: We examined associations between presentation at onset of labor, and tibia and hip bone outcomes at age 17 years in 1971 participants (1062 females) from a UK prospective birth cohort that recruited > 15,000 pregnant women in 1991-1992. Cortical BMC, cross-sectional area (CSA) and bone mineral density (BMD), periosteal circumference, and cross-sectional moment of inertia (CSMI) were measured by peripheral quantitative computed tomography (pQCT) at 50% tibia length. Total hip BMC, bone area, BMD, and CSMI were measured by dual-energy X-ray absorptiometry (DXA). RESULTS: In models adjusted for sex, age, maternal education, smoking, parity, and age, singleton/multiple births, breech presentation (n = 102) was associated with lower tibial cortical BMC (- 0.14SD, 95% CI - 0.29 to 0.00), CSA (- 0.12SD, - 0.26 to 0.02), BMD (- 0.16SD, - 0.31 to - 0.01), periosteal circumference (- 0.14SD, - 0.27 to - 0.01), and CSMI (- 0.11SD, - 0.24 to 0.01). In females only, breech presentation was associated with lower hip CSA (- 0.24SD, - 0.43 to 0.00) but not with other hip outcomes. Additional adjustment for potential mediators (delivery method, birthweight, gestational age, childhood motor competence and adolescent height and body composition) did not substantially affect associations with either tibia or hip outcomes. CONCLUSIONS: These findings suggest that prenatal skeletal loading may exert long-lasting influences on skeletal size and strength but require replication.

Breech presentation is associated with lower bone mass and area: findings from the Southampton Women's Survey.

We compared bone outcomes in children with breech and cephalic presentation at delivery. Neonatal whole-body bone mineral content (BMC) and area were lower in children with breech presentation. At 4 years, no differences in whole-body or spine measures were found, but hip BMC and area were lower after breech presentation. INTRODUCTION: Breech presentation is associated with altered joint shape and hip dysplasias, but effects on bone mineral content (BMC), area (BA) and density (BMD) are unknown. METHODS: In the prospective Southampton Women's Survey mother-offspring cohort, whole-body bone outcomes were measured using dual-energy X-ray absorptiometry (DXA) in 1430 offspring, as neonates (mean age 6 days, n = 965, 39 with a breech presentation at birth) and/or at age 4.1 years (n = 999, 39 breech). Hip and spine bone outcomes were also measured at age 4 years. RESULTS: Neonates with breech presentation had 4.2 g lower whole-body BMC (95% CI -7.4 to - 0.9 g, P = 0.012) and 5.9 cm2 lower BA (- 10.8 to - 1.0 cm2, P = 0.019), but BMD was similar between groups (mean difference - 0.007, - 0.016 to 0.002 g/cm2, P = 0.146) adjusting for sex, maternal smoking, gestational diabetes, mode of delivery, social class, parity, ethnicity, age at scan, birthweight, gestational age and crown-heel length. There were no associations between breech presentation and whole-body outcomes at age 4 years, but, in similarly adjusted models, regional DXA (not available in infants) showed that breech presentation was associated with lower hip BMC (- 0.51, - 0.98 to - 0.04 g, P = 0.034) and BA (- 0.67, - 1.28 to - 0.07 cm2, P = 0.03) but not with BMD (- 0.009, - 0.029 to 0.012 g, P = 0.408), or spine outcomes. CONCLUSIONS: These results suggest that breech presentation is associated with lower neonatal whole-body BMC and BA, which may relate to altered prenatal loading in babies occupying a breech position; these differences did not persist into later childhood. Modest differences in 4-year hip BMC and BA require further investigation.

Identification of the functional pathways altered by placental cell exposure to high glucose: lessons from the transcript and metabolite interactome.

The specific consequences of hyperglycaemia on placental metabolism and function are incompletely understood but likely contribute to poor pregnancy outcomes associated with diabetes mellitus (DM). This study aimed to identify the functional biochemical pathways perturbed by placental exposure to high glucose levels through integrative analysis of the trophoblast transcriptome and metabolome. The human trophoblast cell line, BeWo, was cultured in 5 or 25 mM glucose, as a model of the placenta in DM. Transcriptomic analysis using microarrays, demonstrated 5632 differentially expressed gene transcripts (≥± 1.3 fold change (FC)) following exposure to high glucose. These genes were used to generate interactome models of transcript response using BioGRID (non-inferred network: 2500 nodes (genes) and 10541 protein-protein interactions). Ultra performance-liquid chromatography-mass spectrometry (MS) and gas chromatography-MS analysis of intracellular extracts and culture medium were used to assess the response of metabolite profiles to high glucose concentration. The interactions of altered genes and metabolites were assessed using the MetScape interactome database, resulting in an integrated model of systemic transcriptome (2969 genes) and metabolome (41 metabolites) response within placental cells exposed to high glucose. The functional pathways which demonstrated significant change in response to high glucose included fatty acid ß-oxidation, phospholipid metabolism and phosphatidylinositol phosphate signalling.

Maternal prenatal depression is associated with decreased placental expression of the imprinted gene PEG3.

BACKGROUND: Maternal prenatal stress during pregnancy is associated with fetal growth restriction and adverse neurodevelopmental outcomes, which may be mediated by impaired placental function. Imprinted genes control fetal growth, placental development, adult behaviour (including maternal behaviour) and placental lactogen production. This study examined whether maternal prenatal depression was associated with aberrant placental expression of the imprinted genes paternally expressed gene 3 (PEG3), paternally expressed gene 10 (PEG10), pleckstrin homology-like domain family a member 2 (PHLDA2) and cyclin-dependent kinase inhibitor 1C (CDKN1C), and resulting impaired placental human placental lactogen (hPL) expression. METHOD: A diagnosis of depression during pregnancy was recorded from Manchester cohort participants' medical notes (n = 75). Queen Charlotte's (n = 40) and My Baby and Me study (MBAM) (n = 81) cohort participants completed the Edinburgh Postnatal Depression Scale self-rating psychometric questionnaire. Villous trophoblast tissue samples were analysed for gene expression. RESULTS: In a pilot study, diagnosed depression during pregnancy was associated with a significant reduction in placental PEG3 expression (41%, p = 0.02). In two further independent cohorts, the Queen Charlotte's and MBAM cohorts, placental PEG3 expression was also inversely associated with maternal depression scores, an association that was significant in male but not female placentas. Finally, hPL expression was significantly decreased in women with clinically diagnosed depression (44%, p < 0.05) and in those with high depression scores (31% and 21%, respectively). CONCLUSIONS: This study provides the first evidence that maternal prenatal depression is associated with changes in the placental expression of PEG3, co-incident with decreased expression of hPL. This aberrant placental gene expression could provide a possible mechanistic explanation for the co-occurrence of maternal depression, fetal growth restriction, impaired maternal behaviour and poorer offspring outcomes.

Third trimester placental volume and biometry measurement: A method-development study.

OBJECTIVES: To test the hypothesis that third trimester placental biometry and volume can be measured by two-dimensional (2D) and three-dimensional (3D) ultrasound in utero, determining which method of measurement was most strongly correlated with true placental size ex vivo. METHODS: Singleton pregnancies underwent placental ultrasound within seven days of delivery (n = 87, 29(+3)-41(+5) weeks). Length and width (linear and curvilinear) and depth were estimated. Placental volume (PV) was estimated using 2D ellipse and shell techniques and 3D rotational (15° and 30° rotation angles) and multiplanar (5 and 10 mm slicing intervals) techniques. Measurements were compared to their true correlates following delivery. Intra- and inter-observer reliabilities of candidate placental size estimates were assessed by intraclass correlation coefficient (ICC). RESULTS: Curvilinear placental length (Rs = 0.24, p = 0.031), width (Rs = 0.27, p = 0.013) and depth (Rs = 0.31, p = 0.0056) correlated well with ex vivo measurements. All methods of PV estimation were related to ex vivo volume (Rs ≥ 0.32, p < 0.01) but not placental weight (p > 0.05); 30° rotational estimation demonstrated the strongest biological correlation (Rs = 0.40, p = 0.0004). Intra- and inter-observer placental size measurements intraclass correlation coefficients were suboptimal (0.59-0.70 and 0.10-0.58 respectively). DISCUSSION: We have demonstrated that it is possible to obtain information about the size of the third trimester placenta in utero using 2D and 3D ultrasound. However it is essential that the reliability (particularly interobserver reliability) of these estimates is improved prior to prospective studies to determine their predictive value.

Marvellous to mediocre: findings of national survey of UK practice and provision of care in pregnancies after stillbirth or neonatal death.

BACKGROUND: Pregnancy after stillbirth or neonatal death is an emotionally challenging life-event for women and adequate emotional support during pregnancy should be considered an essential component of quality maternity care. There is a lack of evidence surrounding the role of UK maternity services in meeting womens' emotional and psychological needs in subsequent pregnancies. This study aimed to gain an overview of current UK practice and womens' experiences of care in pregnancy after the death of a baby. METHODS: Online cross-sectional surveys, including open and closed questions, were completed on behalf of 138 United Kingdom (UK) Maternity Units and by 547 women who had experience of UK maternity care in pregnancy after the death of a baby. Quantitative data were analysed descriptively using SPSS software. Open textual responses were managed manually and analysed using the framework method. RESULTS: Variable provision of care and support in subsequent pregnancies was identified from maternity unit responses. A minority had specific written guidance to support care delivery, with a focus on antenatal surveillance and monitoring for complications through increased consultant involvement and technological surveillance (ultrasound/cardiotocography). Availability of specialist services and professionals with specific skills to provide emotional and psychological support was patchy. There was a lack of evaluation/dissemination of developments and innovative practice. Responses across all UK regions demonstrated that women engaged early with maternity care and placed high value on professionals as a source of emotional support. Many women were positive about their care, but a significant minority reported negative experiences. Four common themes summarised womens' perceptions of the most important influences on quality and areas for development: sensitive communication and conduct of staff, appropriate organisation and delivery of services, increased monitoring and surveillance and perception of standard vs. special care. CONCLUSIONS: These findings expose likely inequity in provision of care for UK parents in pregnancy after stillbirth or neonatal death. Many parents do not receive adequate emotional and psychological support increasing the risk of poor health outcomes. There is an urgent need to improve the evidence base and develop specific interventions to enhance appropriate and sensitive care pathways for parents.

Studies of the dynamics of nuclear clustering in human syncytiotrophoblast.

Syncytial nuclear aggregates (SNAs), clusters of nuclei in the syncytiotrophoblast of the human placenta, are increased as gestation advances and in pregnancy pathologies. The origins of increased SNAs are unclear; however, a better appreciation of the mechanism may give insight into placental ageing and factors underpinning dysfunction. We developed three models to investigate whether SNA formation results from a dynamic process of nuclear movement and to generate alternative hypotheses. SNA count and size were measured in placental explants cultured over 16 days and particles released into culture medium were quantified. Primary trophoblasts were cultured for 6 days. Explants and trophoblasts were cultured with and without cytoskeletal inhibitors. An in silico model was developed to examine the effects of modulating nuclear behaviour on clustering. In explants, neither median SNA number (108 SNA/mm(2) villous area) nor size (283 µm(2)) changed over time. Subcellular particles from conditioned culture medium showed a wide range of sizes that overlapped with those of SNAs. Nuclei in primary trophoblasts did not change position relative to other nuclei; apparent movement was associated with positional changes of the syncytial cell membrane. In both models, SNAs and nuclear clusters were stable despite pharmacological disruption of cytoskeletal activity. In silico, increased nuclear movement, adhesiveness and sites of cytotrophoblast fusion were related to nuclear clustering. The prominence of SNAs in pregnancy disorders may not result from an active process involving cytoskeleton-mediated rearrangement of syncytial nuclei. Further insights into the mechanism(s) of SNA formation will aid understanding of their increased presence in pregnancy pathologies.

IFPA meeting 2014 workshop report: Animal models to study pregnancy pathologies; new approaches to study human placental exposure to xenobiotics; biomarkers of pregnancy pathologies; placental genetics and epigenetics; the placenta and stillbirth and fetal growth restriction.

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2014 there were six themed workshops, five of which are summarized in this report. These workshops related to various aspects of placental biology but collectively covered areas of animal models, xenobiotics, pathological biomarkers, genetics and epigenetics, and stillbirth and fetal growth restriction.

IFPA Gábor Than Award Lecture: Recognition of placental failure is key to saving babies' lives.

In high-income countries, placental failure is implicated in up to 65% of cases of stillbirth. Placental failure describes the situation where the placenta cannot meet the fetus' needs and may be the end-result of a variety of underlying pathological processes evident in the placental disc, membranes and umbilical cord. These include lesions with genetic, environmental, infectious, inflammatory, mechanical, metabolic, traumatic or vascular origin. Investigation of placental tissue from stillbirths and from pregnancies at an increased risk of stillbirth has demonstrated changes in macroscopic and microscopic structure which are themselves related to abnormal placental function. A better understanding and identification of placental failure may improve the management of pregnancy complications and of pregnancies after stillbirth (which have a 5-fold increased risk of stillbirth). The majority of current antenatal tests focus on the fetus and its response to the intrauterine environment; few of these investigations reduce stillbirths in low-risk pregnancies. However, some currently used investigations reflect placental development, structure and vascular function, while other investigations employed in clinical research settings such as the evaluation of placental structure and shape have a good predictive value for adverse fetal outcome. In addition, recent studies suggest that biomarkers of placental inflammation and deteriorating placental function can be detected in maternal blood suggesting that holistic evaluation of placental structure and function is possible. We anticipate that development of reliable tests of placental structure and function, coupled to assessment of fetal wellbeing offer a new opportunity to identify pregnancies at risk of stillbirth and to direct novel therapeutic strategies to prevent it.

Systematic review of placental pathology reported in association with stillbirth.

INTRODUCTION: Histopathological examination of the placenta is recommended to determine the cause of stillbirth. Although some reports find causal or contributory placental abnormalities in up to 60% of stillbirths, the significance of such findings in this clinical setting remains uncertain. A systematic review was conducted to i) investigate the likelihood of diagnosing a cause of stillbirth from placental examination and ii) to identify the specific causes of death that can be diagnosed from placental pathology. METHODS: Medline, Embase, Biosis, and Web of Science were searched using the terms "stillbirth", "histopathology", "pathology", and "placenta". Case-reports, narrative review articles and studies that failed to define diagnostic sub-groups were excluded. 473 potential studies were identified. Relevant studies (n = 41) were subdivided into those that investigated causes of stillbirth (n = 13), and those that identified conditions associated with stillbirth (n = 5). The contributory value of placental examination to stillbirth classification was evaluated in 10 studies and the role of specific placental abnormalities in the aetiology of stillbirth in 20 studies. RESULTS: The proportion of stillbirths attributed to a placental cause ranged from 11 to 65%. Classification systems which included multiple placental categories and allowed placental findings to supersede other disorders reported higher rates of placental causes and fewer unexplained stillbirths. Diagnoses were frequently based on qualitative, non-specific terminology. CONCLUSIONS: The utility of histopathological examination of the placenta is affected by the classification system used. International consensus is required for both diagnostic criteria and terminology to describe placental abnormalities and on classification of stillbirths..

Parents' experiences and expectations of care in pregnancy after stillbirth or neonatal death: a metasynthesis.

BACKGROUND: Pregnancy after perinatal death is characterised by elevated stress and anxiety, increasing the risk of adverse short-term and long-term outcomes. OBJECTIVES: This metasynthesis aimed to improve understanding of parents' experiences of maternity care in pregnancy after stillbirth or neonatal death. SEARCH STRATEGY: Six electronic databases were searched using predefined search terms. SELECTION CRITERIA: English language studies using qualitative methods to explore the experiences of parents in pregnancy after perinatal loss, were included subject to quality appraisal framework. DATA COLLECTION AND ANALYSIS: Searches were initiated in December 2011 and finalised in March 2013. Studies were synthesised using an interpretive approach derived from meta-ethnography. MAIN RESULTS: Fourteen studies were included in the synthesis, graded A (no or few flaws, high trustworthiness; n = 5), B (some flaws, unlikely to affect trustworthiness; n = 5) and C (some flaws, possible impact on trustworthiness; n = 4). Three main themes were identified; co-existence of emotions, helpful and unhelpful coping activities and seeking reasssurance through interactions. CONCLUSION: Parents' experiences of pregnancy are profoundly altered by previous perinatal death; conflicted emotions, extreme anxiety, isolation and a lack of trust in a good outcome are commonly reported. Emotional and psychological support improves parents' experiences of subsequent pregnancy, but the absence of an evidence base may limit consistent delivery of optimal care within current services.

Analysis of syncytial nuclear aggregates in preeclampsia shows increased sectioning artefacts and decreased inter-villous bridges compared to healthy placentas.

Syncytial nuclear aggregates (SNAs) are increased in pregnancy complications and include 'true' syncytial knots and inter-villous bridges. Apparent nuclear overlay caused by sectioning artefacts are frequently counted from single sections. Haematoxylin and eosin stained serial sections were assessed for frequency of SNA subtypes in placentas from normal, preeclamptic and fetal growth restricted (FGR) pregnancies. There were more sectioning artefacts and syncytial knots and fewer bridges in samples from preeclampsia compared to controls. There were no significant differences between FGR and control samples. This suggests the villous tree in preeclampsia has less inherent structural support and trophoblast cell dynamics are different.

Duration and method of tissue storage alters placental morphology - implications for clinical and research practice.

We assessed whether placental morphology is affected by placental storage before fixation. Fresh tissue from uncomplicated pregnancies (n = 10) was fixed immediately and further samples were stored dry, in PBS or culture medium for 24, 48 or 72 h at 4 °C. Placental morphology quantified using image analysis software found no difference in syncytial nuclear aggregates, cytokeratin 7, CD45 or Ki67 immunostaining irrespective of duration or mode of storage. The number of blood vessels per villus (CD31) was reduced in all conditions after 72 h (p < 0.05). Distal villous hypoplasia increased after 72 h (p < 0.05). Ideally, storage time should be minimised to ≤48 h prior to morphological or qualitative analysis.

Investigating the association of villitis of unknown etiology with stillbirth and fetal growth restriction - a systematic review.

Villitis of unknown etiology (VUE) is an inflammatory condition reported to occur in up to 15% of term placentas. It has been reported in association with fetal growth restriction and antepartum stillbirth. This study aimed to investigate the strength of these associations by completing a systematic review using established guidelines. 618 potentially relevant studies were identified. After exclusion of studies that were not relevant or of insufficient quality, a total of 24 case-control and cohort studies were included in the review. Studies were grouped according to whether their main focus was VUE, fetal growth restriction or stillbirth. A methodological quality assessment carried out for each group demonstrated significant heterogeneity in study design. VUE occurs more frequently in placentas of growth restricted infants. A significant link between VUE and stillbirth could not be reliably established because there were too few published studies. Further research into the pathological effects of VUE using robust protocols and reporting methods is required.

Syncytial nuclear aggregates in normal placenta show increased nuclear condensation, but apoptosis and cytoskeletal redistribution are uncommon.

INTRODUCTION: Syncytial nuclear aggregates (SNAs) are increased in pregnancy complications; however, little is known about their origin or function. This study aimed to characterise SNAs in more detail than has been reported previously. METHODS: Immunohistochemistry and morphological examination at the light and ultrastructural level were used to determine the nature and structure of SNAs. RESULTS: SNAs comprising bridges and syncytial knots had similar frequency with 974 per mm3 of villous tissue (IQR 717-1193) and 833 per mm3 (IQR 766-1190), respectively while there were approximately four times as many sectioning artefacts than knots and bridges combined. SNAs had increased proportions of condensed nuclei compared to the remaining syncytiotrophoblast (33.3% vs. 8.9%) and decreased proportions of euchromatic nuclei (0.0% vs. 16.2%), as assessed by examination of an electron micrograph archive. SNAs showed little evidence of apoptosis, with weak positivity for the apoptosis markers M30-neoepitope at 16.6% and TUNEL at 10.0%; strong staining was rarely seen for either marker. Immunofluorescence demonstrated rare association of actin (α, ß or γ) with SNAs, whereas tubulin was in close proximity to SNAs and cytokeratin was seen within and surrounding SNAs. DISCUSSION: M30-positive SNAs traced through serial sections were significantly more likely to be syncytial knots or sectioning artefacts than bridges. Nuclei within SNAs showed signs consistent with degeneration; however, this is unlikely to be an apoptotic process. There are few changes in configuration of cytoskeletal proteins around SNAs. CONCLUSIONS: These data suggest that the biogenesis and functional significance of SNAs still require resolution.

Correlation between abnormal placental appearance at routine 2nd trimester ultrasound scan and histological examination of the placenta after birth.

Ultrasound imaging of the placenta and its relationship to poor perinatal outcome has been studied since 1973. Studies have predominantly focussed on placental morphology in the third trimester or in high-risk pregnancies. We aimed to correlate abnormal placental appearances identified in the second trimester with histological appearances. We present four cases of abnormal placental morphology detected at the 20 week routine ultrasound scan in low-risk women and relate them to histological origins, which often involved areas of villous infarction. Abnormal placental appearances at routine second trimester anomaly ultrasound scans might identify women with placental dysfunction who merit increased fetal surveillance in the third trimester.

A high-throughput colorimetric-assay for monitoring glucose consumption by cultured trophoblast cells and placental tissue.

Diabetes mellitus is associated with abnormalities in placental structure and function and significant pregnancy complications. In vitro studies to investigate the effect of hyperglycaemia on trophoblast structure and function require an accurate, inexpensive and reliable assay to monitor the concentration of glucose in culture medium. We have modified and validated an existing protocol for use with a 96-well microplate. This provides a specific, high-throughput assay which accurately measures culture media glucose concentrations between 7 and 30 mM, without spectral interferences by phenol red or sera. Use of this assay revealed that the concentration of glucose in BeWo cell cultures remains stable for 48 h. In contrast placental explants rapidly consume glucose thus the concentration in culture media significantly decreases over 12 h necessitating more frequent replenishment in order to maintain the desired concentration. We therefore advise researchers to monitor glucose concentrations in in vitro investigations modelling the effect of diabetes mellitus on placental structure and function.