The role of the placenta in spontaneous preterm labor and delivery with intact membranes

Characterising delayed villous maturation: A narrative literature review

The normal development of the placenta is vital for fetal growth and a healthy pregnancy outcome. Delayed villous maturation (DVM) is a placental lesion that has been implicated in stillbirth. In DVM, villi do not maturate adequately for their gestational age. DVM is characterised by larger and fewer terminal placental villi, low numbers of syncytial knots, and thicker and fewer vasculosyncytial membranes. DVM is most commonly reported in conjunction with maternal diabetes; however, the occurrence of idiopathic DVM suggests that there may be multiple mechanistic pathways that contribute to DVM. DVM can only be diagnosed through histopathological examination after birth, and there is significant interobserver variability in diagnosis. Establishing objective criteria to distinguish between DVM and healthy placentas is key to increasing the understanding of DVM. Vasculosyncytial membrane count, numbers of syncytial knots and CD15, among others, have been presented as potential diagnostic criteria in the literature. This review aims to compile information on DVM, including the pathophysiology, conditions that have reported associations with DVM and potential markers that could be used as criteria to differentiate between DVM and healthy placentas.

Placental histopathological abnormalities in adverse obstetric outcomes: a retrospective cross-sectional study at Sultan Qaboos University Hospital

INTRODUCTION

Placenta is a vital organ with highly specialized functions. According to the Perinatal Section of the Pediatric Pathology Society, placental histopathological abnormalities are typically categorized into maternal vascular hypoperfusion, fetal thrombotic vasculopathy, and inflammatory lesions. This study aims to assess the placental histopathological abnormality results in relation to adverse obstetric outcomes and to investigate whether specific placental abnormalities are associated with particular adverse outcomes.

METHODS

A retrospective cross-sectional study was conducted between January 2017 and January 2020 including all women who were admitted to Sultan Qaboos University Hospital with an adverse obstetric outcome who met the inclusion criteria, and whose placentas were sent for histopathological examination.

RESULTS

A total of 191 women were included in the study. The most common adverse obstetric outcomes included preterm labor (25.1%), fetal growth restriction (FGR) (19.4%), preeclampsia and related complications (15%), placental abruption (14.1%), and chorioamnionitis (14%). 74% of women had abnormal placental findings. Among women with preterm labor, inflammatory lesions were present in 56.3% of cases (p = 0.006). Fetal thrombotic vasculopathy lesions were present in 13.5% of FGR cases (p = 0.037). In preeclampsia cases, maternal under perfusion lesions were present in 79% of cases (p = 0.013).

CONCLUSION

Placental histopathological examination is an important tool for assessing perinatal outcomes. Correlating placental findings with specific obstetrical conditions and adverse outcomes provides valuable information that can assist obstetricians in developing appropriate management plans for future pregnancies.

Placental differences between severe fetal growth restriction and hypertensive disorders of pregnancy requiring early preterm delivery: morphometric analysis of the villous tree supported by artificial intelligence

BACKGROUND

The great obstetrical syndromes of fetal growth restriction and hypertensive disorders of pregnancy can occur individually or be interrelated. Placental pathologic findings often overlap between these conditions, regardless of whether 1 or both diagnoses are present. Quantification of placental villous structures in each of these settings may identify distinct differences in developmental pathways.

OBJECTIVE

This study aimed to determine how the quantity and surface area of placental villi and vessels differ between severe, early-onset fetal growth restriction with absent or reversed umbilical artery Doppler indices and hypertensive disorders of pregnancy or the 2 conditions combined among subjects with disease severity that warrant early preterm delivery. We hypothesized that the trajectories of placental morphogenesis diverge after a common initiating insult of deep defective placentation. Specifically, we postulated that only villi are affected in pregnancy-related hypertension, whereas both villous and vascular structures are proportionally diminished in severe fetal growth restriction with no additional effect when hypertension is concomitantly present.

STUDY DESIGN

In this retrospective cohort study, paraffin-embedded placental tissue was obtained from 4 groups, namely (1) patients with severe fetal growth restriction with absent or reversed umbilical artery end-diastolic velocities and hypertensive disorders of pregnancy, (2) patients with severe fetal growth restriction with absent or reversed umbilical artery Doppler indices and no hypertension, (3) gestational age-matched, appropriately grown pregnancies with hypertensive disease, and (4) gestational age-matched, appropriately grown pregnancies without hypertension. Dual immunohistochemistry for cytokeratin-7 (trophoblast) and CD34 (endothelial cells) was performed, followed by artificial intelligence-driven morphometric analyses. The number of villi, total villous area, number of fetoplacental vessels, and total vascular area across villi within a uniform region of interest were quantified. Quantitative analyses of placental structures were modeled using linear regression.

RESULTS

Placentas from pregnancies complicated by hypertensive disorders of pregnancy exhibited significantly fewer stem villi (-282 stem villi; 95% confidence interval, -467 to -98; P<.01), a smaller stem villous area (-4.3 mm2; 95% confidence interval, -7.3 to -1.2; P<.01), and fewer stem villous vessels (-4967 stem villous vessels; 95% confidence interval, -8501 to -1433; P<.01) with no difference in the total vascular area. In contrast, placental abnormalities in cases with severe growth restriction were limited to terminal villi with global decreases in the number of villi (-873 terminal villi; 95% confidence interval, -1501 to -246; P<.01), the villous area (-1.5 mm2; 95% confidence interval, -2.7 to -0.4; P<.01), the number of blood vessels (-5165 terminal villous vessels; 95% confidence interval, -8201 to -2128; P<.01), and the vascular area (-0.6 mm2; 95% confidence interval, -1.1 to -0.1; P=.02). The combination of hypertension and growth restriction had no additional effect beyond the individual impact of each state.

CONCLUSION

Pregnancies complicated by hypertensive disorders of pregnancy exhibited defects in the stem villi only, whereas placental abnormalities in severely growth restricted pregnancies with absent or reversed umbilical artery end-diastolic velocities were limited to the terminal villi. There were no significant statistical interactions in the combination of growth restriction and hypertension, suggesting that distinct pathophysiological pathways downstream of the initial insult of defective placentation are involved in each entity and do not synergize to lead to more severe pathologic consequences. Delineating mechanisms that underly the divergence in placental development after a common inciting event of defective deep placentation may shed light on new targets for prevention or treatment.

Predictive Value of the sFlt-1/PlGF Ratio and Interleukin-6 for the Presence of Placental Lesions in Spontaneous Preterm Labor with Intact Membranes with Delivery within 7 Days

INTRODUCTION

The aim of the study was to identify predictive values of the soluble fms-like tyrosine kinase/placental growth factor (sFlt-1/PlGF) ratio and interleukin (IL)-6, assessed with a clinically available method in a large-volume biochemistry laboratory, in maternal blood, amniotic fluid, and umbilical cord blood for the presence of the placental lesions consistent with maternal vascular malperfusion (MVM) and acute histological chorioamnionitis (HCA), respectively.

METHODS

This retrospective study included 92 women with preterm labor with intact membranes (PTL) delivered within 7 days of admission with gestational ages between 22+0 and 34+6 weeks. The sFlt-1/PlGF ratio and IL-6 were assessed in stored samples of maternal serum, amniotic fluid, and umbilical cord serum using Elecsys® sFlt-1, PlGF, and IL-6 immunoassays.

RESULTS

Women with MVM had a higher sFlt-1/PlGF ratio in the maternal serum, compared to those without MVM (19.9 vs. 4.6; p < 0.0001), but not in the amniotic fluid or umbilical cord blood. A cut-off value of 8 for the sFlt-1/PlGF ratio in maternal serum was identified as optimal for predicting MVM in patients with PTL. Women with HCA had higher concentrations of IL-6 in maternal serum, compared to those without HCA (11.1 pg/mL vs. 8.4 pg/mL; p = 0.03), amniotic fluid (9,216 pg/mL vs. 1,423 pg/mL; p < 0.0001), and umbilical cord blood (20.7 pg/mL vs. 10.7 pg/mL, p = 0.002). Amniotic-fluid IL-6 showed the highest predictive value. A cut-off value of IL-6 concentration in the amniotic fluid of 5,000 pg/mL was found to be optimal for predicting HCA in PTL.

CONCLUSION

Maternal serum sFlt-1/PlGF and amniotic fluid IL-6 concentrations can be used for liquid biopsy to predict placental lesions in women with PTL who deliver within 7 days.

Metabolomic analysis of the human placenta reveals perturbations in amino acids, purine metabolites, and small organic acids in spontaneous preterm birth

Spontaneous preterm delivery presents one of the most complex challenges in obstetrics and is a leading cause of perinatal morbidity and mortality. Although it is a common endpoint for multiple pathological processes, the mechanisms governing the etiological complexity of spontaneous preterm birth and the placental responses are poorly understood. This study examined placental tissues collected between May 2019 and May 2022 from a well-defined cohort of women who experienced spontaneous preterm birth (n = 72) and healthy full-term deliveries (n = 30). Placental metabolomic profiling of polar metabolites was performed using Ultra-High Performance Liquid Chromatography/Mass Spectrometry (UHPLC/MS) analysis. The resulting data were analyzed using multi- and univariate statistical methods followed by unsupervised clustering. A comprehensive metabolomic evaluation of the placenta revealed that spontaneous preterm birth was associated with significant changes in the levels of 34 polar metabolites involved in intracellular energy metabolism and biochemical activity, including amino acids, purine metabolites, and small organic acids. We found that neither the preterm delivery phenotype nor the inflammatory response explain the reported differential placental metabolome. However, unsupervised clustering revealed two molecular subtypes of placentas from spontaneous preterm pregnancies exhibiting differential enrichment of clinical parameters. We also identified differences between early and late preterm samples, suggesting distinct placental functions in early spontaneous preterm delivery. Altogether, we present evidence that spontaneous preterm birth is associated with significant changes in the level of placental polar metabolites. Dysregulation of the placental metabolome may underpin important (patho)physiological mechanisms involved in preterm birth etiology and long-term neonatal outcomes.

The association between human chorionic gonadotropin and adverse pregnancy outcomes: a systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the association between human chorionic gonadotropin and adverse pregnancy outcomes.

DATA SOURCES

Medline, Embase, PubMed, and Cochrane were searched in November 2021 using Medical Subject Headings (MeSH) and relevant key words.

STUDY ELIGIBILITY CRITERIA

This analysis included published full-text studies of pregnant women with serum human chorionic gonadotropin testing between 8 and 28 weeks of gestation, investigating fetal outcomes (fetal death in utero, small for gestational age, preterm birth) or maternal factors (hypertension in pregnancy: preeclampsia, pregnancy-induced hypertension, placental abruption, HELLP syndrome, gestational diabetes mellitus).

METHODS

Studies were extracted using REDCap software. The Newcastle-Ottawa scale was used to assess for risk of bias. Final meta-analyses underwent further quality assessment using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) method.

RESULTS

A total of 185 studies were included in the final review, including the outcomes of fetal death in utero (45), small for gestational age (79), preterm delivery (62), hypertension in pregnancy (107), gestational diabetes mellitus (29), placental abruption (17), and HELLP syndrome (2). Data were analyzed separately on the basis of categorical measurement of human chorionic gonadotropin and human chorionic gonadotropin measured on a continuous scale. Eligible studies underwent meta-analysis to generate a pooled odds ratio (categorical human chorionic gonadotropin level) or difference in medians (human chorionic gonadotropin continuous scale) between outcome groups. First-trimester low human chorionic gonadotropin levels were associated with preeclampsia and fetal death in utero, whereas high human chorionic gonadotropin levels were associated with preeclampsia. Second-trimester high human chorionic gonadotropin levels were associated with fetal death in utero and preeclampsia.

CONCLUSION

Human chorionic gonadotropin levels are associated with placenta-mediated adverse pregnancy outcomes. Both high and low human chorionic gonadotropin levels in the first trimester of pregnancy can be early warning signs of adverse outcomes. Further analysis of human chorionic gonadotropin subtypes and pregnancy outcomes is required to determine the diagnostic utility of these findings in reference to specific cutoff values.

Anti-β2-glycoprotein I antibody maybe a novel biomarker of spontaneous preterm birth

BACKGROUND

Spontaneous preterm birth is challenging to prevent. Only few predictors of spontaneous preterm birth risk have been reported, and further studies on spontaneous preterm birth should be conducted to reduce the number of cases.

PURPOSE

The aim of the present study was to explore if anti-β₂-glycoprotein I antibody can be used to predict the risk of spontaneous preterm birth, and its clinical value in assessing the risk of spontaneous preterm birth.

METHODS

A total of 302 pregnant women who had delivered between January 2019 and December 2021 were enrolled into the study. The subjects were assigned to the case group (28-33⁺⁶ weeks, n = 41; 34-36⁺⁶ weeks, n = 96) and control group (37-42 weeks, n = 165) according to the gestational period. The age, body mass index, and gestational days of the two groups were recorded. Blood samples were collected and the levels of anti-β₂-glycoprotein I antibody, white blood cell, red blood cell, hemoglobin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, urea, creatinine, glucose, triglyceride, and total cholesterol were evaluated. Pregnant women diagnosed with sPTB that met the standards after evaluation by the clinician were included in the study.

RESULTS

The level of anti-β₂-glycoprotein I antibody was higher in case group than in the control group [(23.93 ± 8.11)Ru/mL vs (11.50 ± 5.33)Ru/mL]. The results showed that anti-β₂-glycoprotein I antibody was an independent risk factor for spontaneous preterm birth. The area under ROC curve of anti-β₂-glycoprotein I antibody to predict spontaneous preterm birth was 0.8875 (95%CI 0.8443-0.9307). The highest predicted value of anti-β₂-glycoprotein I antibody was 16.49Ru/ml.

CONCLUSION

Anti-β₂-glycoprotein I antibody has a high clinical significance and can be used by clinicians to evaluate the probability of spontaneous preterm birth.

Dysregulation of integrin αvβ3 and α5β1 impedes migration of placental endothelial cells in fetal growth restriction

Placentas from pregnancies complicated by severe early-onset fetal growth restriction (FGR) exhibit diminished vascular development mediated by impaired angiogenesis, but underlying mechanisms remain unknown. In this study, we show that FGR endothelial cells demonstrate inherently reduced migratory capacity despite the presence of fibronectin, a matrix protein abundant in placental stroma that displays abnormal organization in FGR placentas. Thus, we hypothesized that aberrant endothelial-fibronectin interactions in FGR are a key mechanism underlying impaired FGR endothelial migration. Using human fetoplacental endothelial cells isolated from uncomplicated term control and FGR pregnancies, we assessed integrin α5β1 and αvβ3 regulation during cell migration. We show that endothelial integrin α5β1 and αvβ3 interactions with fibronectin are required for migration and that FGR endothelial cells responded differentially to integrin inhibition, indicating integrin dysregulation in FGR. Whole-cell expression was not different between groups. However, there were significantly more integrins in focal adhesions and reduced intracellular trafficking in FGR. These newly identified changes in FGR endothelial cellular processes represent previously unidentified mechanisms contributing to persistent angiogenic deficiencies in FGR.

Analysis of the relationship between placental histopathological aspects of preterm and term birth

OBJECTIVES

This study aims to establish a correlation between placental histopathological and immunohistochemical (IHC) changes and preterm birth with fetal growth restriction (FGR, formerly called intrauterine growth restriction - IUGR).

PATIENTS, MATERIALS, AND METHODS

This prospective study was performed on a group of 30 parturients, with singleton gestation, of which 15 patients gave birth at term, and the other 15 patients gave birth prematurely. After the statistical correlation of the clinical and demographic data with premature birth (PB) and term birth (TB), we performed histological and IHC research on the respective placentae. To observe normal and pathological microscopic placental structures, we used the Hematoxylin-Eosin (HE) and Periodic Acid Schiff-Hematoxylin (PAS-H) classical stainings, but also special immunostaining with anti-cluster of differentiation 34 (CD34) and anti-vascular endothelial growth factor (VEGF) antibodies.

RESULTS

We found a statistically significant difference between the TB∕PB categories and the age of the patients, their antepartum weight, the weight of the newborns, and the placenta according to the sex of the newborn. Histological analysis revealed in the case of TB, small areas of perivillous amyloid deposition, with the significant extension of these areas both intravillous and perivillous in the case of PB. Massive intravillous calcifications, syncytial knots, and intravillous vascular thrombosis were also frequently present in PB. With PAS-H staining were highlighted the intra∕extravillous vascular basement membranes, but especially the massive fibrin deposits rich in glycosaminoglycans. By the IHC technique with the anti-CD34 antibody, we noticed the numerical vascular density, higher in the case of TB, but in the case of PB, there were large areas of placental infarction, with a lack of immunostaining in these areas. Through the anti-VEGF antibody, we observed the presence of signal proteins that determined and stimulated the formation of neoformation vessels in the areas affected by the lack of post-infarction placental vascularization. We observed a highly significant difference between placental vascular density between TB∕PB and newborn weight, sex, or placental weight.

CONCLUSIONS

Any direct proportional link between the clinical maternal-fetal and histological elements yet studied must be considered. Thus, establishing an antepartum risk group can prevent a poor pregnancy outcome.

Intra-amniotic inflammation and birth weight in pregnancies with preterm labor with intact membranes: A retrospective cohort study

OBJECTIVE

To assess the association between newborn birth weight and the presence of intra-amniotic infection, presence of sterile intra-amniotic inflammation, and absence of intra-amniotic inflammation in pregnancies with preterm labor with intact membranes.

METHODS

A total of 69 pregnancies with preterm labor with intact membranes between gestational ages 22 + 0 and 34 + 6 weeks who delivered within seven days of admission were included in this retrospective cohort study. Transabdominal amniocentesis to determine the presence of microorganisms and/or their nucleic acids in amniotic fluid (through culturing and molecular biology methods) and intra-amniotic inflammation (according to amniotic fluid interleukin-6 concentrations) were performed as part of standard clinical management. The participants were further divided into three subgroups: intra-amniotic infection (presence of microorganisms and/or nucleic acids along with intra-amniotic inflammation), sterile intra-amniotic inflammation (intra-amniotic inflammation alone), and without intra-amniotic inflammation. Birth weights of newborns were expressed as percentiles derived from the INTERGROWTH-21st standards for (i) estimated fetal weight and (ii) newborn birth weight.

RESULTS

No difference in birth weights, expressed as percentiles derived from the standard for estimated fetal weight, was found among the women with intra-amniotic infection, with sterile intra-amniotic inflammation, and without intra-amniotic inflammation (with infection, median 29; with sterile inflammation, median 54; without inflammation, median 53; p = 0.06). Differences among the subgroups were identified in the birth weight rates, expressed as percentiles derived from the standard for estimated fetal weight, which were less than the 10th percentile (with infection: 20%, with inflammation: 13%, without inflammation: 0%; p = 0.04) and 25th percentile (with infection: 47%, with inflammation: 31%, without inflammation: 9%; p = 0.01). No differences among the subgroups were observed when percentiles of birth weight were derived from the birth weight standard.

CONCLUSIONS

The presence of intra-amniotic inflammatory complications in pregnancies with preterm labor with intact membranes prior to the gestational age of 35 weeks was associated with a higher rate of newborns with birth weight less than the 10th and 25th percentile, when percentiles of birth weight were derived from the standard for estimated fetal weight.