Fetal membrane imaging and the prediction of preterm birth: a systematic review, current issues, and future directions

Histologic Evidence of Epithelial-Mesenchymal Transition and Autophagy in Human Fetal Membranes

Preterm, prelabor rupture of the human fetal membranes (pPROM) is involved in 40% of spontaneous preterm births worldwide. Cellular-level disturbances and inflammation are effectors of membrane degradation, weakening, and rupture. Maternal risk factors induce oxidative stress (OS), senescence, and senescence-associated inflammation of the fetal membranes as reported mechanisms related to pPROM. Inflammation can also arise in fetal membrane cells (amnion/chorion) due to OS-induced autophagy and epithelial-mesenchymal transition (EMT). Autophagy, EMT, and their correlation in pPROM, along with OS-induced autophagy-related changes in amnion and chorion cells in vitro, were investigated. Immunocytochemistry staining of cytokeratin-18 (epithelial marker)/vimentin (mesenchymal marker) and proautophagy-inducing factor LC3B were performed in fetal membranes from pPROM, term not in labor, and term labor. Ultrastructural changes associated with autophagy were verified by transmission electron microscopy of the fetal membranes and in cells exposed to cigarette smoke extract (an OS inducer). EMT and LC3B staining was compared in the chorion from pPROM versus term not in labor. Transmission electron microscopy confirmed autophagosome formation in pPROM amnion and chorion. In cell culture, autophagosomes were formed in the amnion with OS treatment, while autophagosomes were accumulated in both cell types with autophagy inhibition. This study documents the association between pPROMs and amniochorion autophagy and EMT, and supports a role for OS in inducing dysfunctional cells that increase inflammation, predisposing membranes to rupture.

Incidence of preterm premature rupture of membranes and its association with inter-pregnancy interval: a prospective cohort study

Preterm premature rupture of membranes is one of the causes of premature birth and perinatal deaths, particularly in developing countries due to poor access and availability of medical resources to manage and sustain the pregnancy to term. Although, several risk factors for preterm premature rupture of membranes were identified, its association with inter-pregnancy interval was understudied. Therefore, we aimed to assess the incidence of preterm premature rupture of membranes and its association with inter-pregnancy interval in urban South Ethiopia. A community-based prospective cohort study was conducted among 2578 pregnant women, and followed until delivery. A generalized linear model for binary outcome was applied for the analysis, using a 95% confidence level and P-value. The incidence of preterm premature rupture of membranes was 2%, 95% CI: 2%, 3%. However, the incidence was varied across the months of inter-pregnancy intervals 4% (< 18 months), 2% (18–23 months) and 1% (24–60 months). The risk of preterm premature rupture of membranes was nearly three times (ARR = 2.59, 95%CI: 1.27, 5.29) higher for women with inter-pregnancy intervals < 18 months than 24–60 months. Inter-pregnancy interval under 18 months increases the risk of preterm premature rupture of membranes, highlighting the need to improve pregnancy spacing in the community.

Magnetic resonance imaging of the supra-cervical fetal membrane detects an increased risk of prelabor rupture of membranes

OBJECTIVE

In 10% of term deliveries and 40% of preterm deliveries, the fetal membrane (FM) ruptures before labor. However, the ability to predict these cases of premature rupture of membranes (PROM) and preterm premature rupture of membranes (PPROM) is very limited. In this paper, our objective was to determine whether a prediction method based on T2 weighted magnetic resonance imaging (MRI) of the supra-cervical FM could predict PROM and PPROM.

METHODS

This prospective cohort study enrolled 77 women between the 28th and 37th weeks of gestation. Two indicators of fetal membrane defects, including prolapsed depth >5 mm and signal abnormalities, are investigated for our prediction. Fisher's exact test was used to determine whether prolapsed depth >5 mm and/or signal abnormalities were associated with PROM and PPROM. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for prolapsed depth >5 mm, signal abnormalities, and the combination of prolapsed depth >5 mm and signal abnormalities.

RESULT

Among 12 women with PROM (5 preterm and 7 term, prior to labor onset), 9 had membrane prolapse >5 mm and 5 had FM signal abnormalities. Among 65 women with rupture of membranes at term, 2 had membrane prolapse >5 mm and 1 had signal abnormalities. By Fisher's exact test both indicators, membrane prolapse >5 mm and signal abnormalities, were associated with PROM (P<0.001, P<0.001) and PPROM (P=0.001, P<0.001). Additionally, membrane prolapse >5 mm, signal abnormalities, and the combination of the two indicators all demonstrated high specificity for predicting PROM (96.9%, 98.5%, and 100%, respectively) and PPROM (90.3%, 97.2%, and 100%, respectively).

CONCLUSION

MRI can distinguish the supra-cervical fetal membrane in vivo and may be able to identify women at high risk of PPROM.

Comprehensive quantitative characterization of the human term amnion proteome

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We report an unprecedented quantitative high coverage of the human amnion proteome.

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We identified novel proteins that hold great promise for understanding fetal membrane biology.

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Together, this comprehensive proteome provides a basis for the evaluation of pre-term or diseased fetal membranes.

The loss of fetal membrane (FM) integrity and function at an early time point during pregnancy can have devastating consequences for the fetus and the newborn. However, biomaterials for preventive sealing and healing of FMs are currently non-existing, which can be partly attributed to the current fragmentary knowledge of FM biology. Despite recent advances in proteomics analysis, a robust and comprehensive description of the amnion proteome is currently lacking. Here, by an optimized protein sample preparation and offline fractionation before liquid chromatography coupled to mass spectrometry (LC-MS) analysis, we present a characterization of the healthy human term amnion proteome, which covers more than 40% of the previously reported transcripts in similar RNA sequencing datasets and, with more than 5000 identifications, greatly outnumbers previous reports. Together, beyond providing a basis for the study of compromised and preterm ruptured FMs, this comprehensive human amnion proteome is a stepping-stone for the development of novel healing-inducing biomaterials. The proteomic dataset has been deposited in the ProteomeXchange Consortium with the identifier PXD019410.

Identifying the associated factors with onset of preterm PROM compared with term PROM - A retrospective cross-sectional study

OBJECTIVE

To determine the risk factors associated with the preterm premature rupture of membranes (p-PROM).

MATERIALS AND METHODS

This retrospective cross-sectional study assessed 110 p-PROM cases from among 6642 deliveries at a Japanese perinatal medical center, from June 2016 to September 2018. The control group comprised 220 term PROM (t-PROM) cases. We excluded cases with artificial PROM or rupture of membranes after labor, those with multiple pregnancies, those with p-PROM at 36 weeks and those with t-PROM at 37 weeks. In order to compare p-PROM with t-PROM, univariate and multivariate analysis were performed using several clinical factors at the time of PROM onset.

RESULTS

The p-PROM group included 110 cases with 14-35 weeks PROM, and the t-PROM group included 220 cases with 38-41 weeks PROM. Eleven factors were identified as significant factors on the univariate analysis. A history of cervical conization (OR 37.5, 95% CI: 2.31-607.1), cervical length <25 mm at 28 weeks (OR 9.31, 95% CI: 1.76-49.3), negative Lactobacillus (OR 4.01, 95% CI: 1.18-13.7), and bleeding during the second trimester (OR 3.35, 95% CI: 1.18-9.53) were identified as significant factors by the multivariate analysis. Based on the risk factors identified during the multivariate analysis, we divided the 330 cases in the following three groups: 0 group (n = 244), 1 group (n = 60), and 2-4 group (n = 26). The ratio of p-PROM:t-PROM was calculated and compared for each group. The ratios were 21% (0 group), 57% (1 group), and 100% (2-4 group), indicating statistically significant differences between the groups (p < 0.001).

CONCLUSION

We found that the following four factors were associated with p-PROM: history of cervical conization, cervical length <25 mm at 28 weeks, negative Lactobacillus, and bleeding during the second trimester. Our results suggest that we can identify patients who are at increased risk for p-PROM, based on these factors. Further research is necessary to determine the optimal treatment approach for these patients to prevent p-PROM.

The Immunological Role of the Placenta in SARS-CoV-2 Infection-Viral Transmission, Immune Regulation, and Lactoferrin Activity

A pandemic of acute respiratory infections, due to a new type of coronavirus, can cause Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) and has created the need for a better understanding of the clinical, epidemiological, and pathological features of COVID-19, especially in high-risk groups, such as pregnant women. Viral infections in pregnant women may have a much more severe course, and result in an increase in the rate of complications, including spontaneous abortion, stillbirth, and premature birth-which may cause long-term consequences in the offspring. In this review, we focus on the mother-fetal-placenta interface and its role in the potential transmission of SARS-CoV-2, including expression of viral receptors and proteases, placental pathology, and the presence of the virus in neonatal tissues and fluids. This review summarizes the current knowledge on the anti-viral activity of lactoferrin during viral infection in pregnant women, analyzes its role in the pathogenicity of pandemic virus particles, and describes the potential evidence for placental blocking/limiting of the transmission of the virus.

Hyperechoic amniotic membranes in patients with preterm premature rupture of membranes (p-PROM) and pregnancy outcome

OBJECTIVES

The early identification of women with preterm premature rupture of membranes (p-PROM) who are at higher risk of imminent delivery remains challenging. The aim of our study was to evaluate if an increased echogenicity of the amniotic membranes may represent a sonographic marker of impending delivery in women with p-PROM.

METHODS

This was a prospective study including women with singleton pregnancies and diagnosis of p-PROM between 22 and 37 gestational weeks. A sonographic examination was performed within 24 h from the hospital admission and the appearance of the amniotic membranes close to the internal os was specifically evaluated. The membranes were defined as hyperechoic when their echogenicity was similar to that of the fetal bones or normoechoic in the other cases. The primary aim of the study was to compare the admission to spontaneous onset of labor interval and the pregnancy outcome between the cases of p-PROM with and without hyperechoic membranes.

RESULTS

Overall, 45 women fulfilled the inclusion criteria with similar characteristics at admission. In women with hyperechoic membranes, the admission to spontaneous onset of labor interval was significantly shorter (11.5 [5.3-25.0] vs. 3.0 [1.5-9.0] p=0.04) compared to women with normo-echoic membranes. At binomial logistic regression after adjustment for GA at hospital admission, the presence of hyperechoic membranes was found as the only independent predictor of spontaneous onset of labor ≤72 h (aOR: 6.1; 95% CI: 1.0-36.9).

CONCLUSIONS

The presence of hyperechoic membranes is associated with a 6-fold higher incidence of spontaneous onset of labor within 72 h independently from the gestational age at p-PROM.

Prediction of Preterm Delivery by Ultrasound Measurement of Cervical Length and Funneling Changes of the Cervix in Pregnant Women with Preterm Labor at 28-34 weeks of Gestation

The present study aims at predicting preterm delivery by ultrasound measurement of cervical length and the funneling changes of the cervix in preterm labor pregnant women at 28-34 weeks of gestation. The present study is an observational-analytical study with a prospective cohort design. The statistical population of this study includes 70 preterm labor pregnant women who were referred to Tehran hospitals from March 2018 to March 2020. The case group includes 35 women who had short cervical length as well as the funneling changes of the cervix. The control group includes 35 patients whose cervical length was normal and lacked the funneling changes of the cervix. The samples were analyzed after being collected. The mean age of mothers was 29.22 years in the short cervical length group (SD=4.64) and 28.45 years in the normal cervical length group (SD=4.59). The mean length of cervical length was 17.34 mm in the short cervical length group (SD=5.64) and 38.74 mm in the normal cervical length group (SD=4.53). In the case group, the delivery occurred two or seven days after the first visit; as for the proper cervical length group without funneling changes, the delivery occurred 14 days after the first delivery. Thus, the difference is statistically significant (P=0.00). In terms of the preterm delivery before week 34, there was also a significant difference between the short and normal cervical length group, as well as the groups with the funnel-shaped and non-funnel-shaped cervix (P=0.00). However, in terms of post-term delivery before week 37, there was no significant difference between short and normal cervical length groups as well as funneled and non-funneled groups (P=0.78). In terms of term labor, there was a significant difference between short and normal cervical length groups, as well as funneled and non-funneled groups (P=0.00). In investigating the cut-off point with good sensitivity, it was indicated that the cervical length and cervical funneling in pregnant women at risk predict preterm labor before week 34. With the measurement of cervical length and diagnosis of cervical funneling by applying ultrasound, preterm delivery before week 34 can be predicted. Therefore, neonatal mortality and morbidity rates can be reduced in this way.

ABCA1 plays an anti-inflammatory role by affecting TLR4 at the feto-maternal interface

AIMS

This study aimed to evaluate the function and pathway of ATP-binding cassette transporter member A1 (ABCA1)-induced anti-inflammatory response in cells at the feto-maternal interface.

MAIN METHODS

The primary amniotic mesenchymal cells (AMCs), chorion cells and decidual cells were isolated from placental membranes of women with uncomplicated pregnancies at full-term (not in labor) using enzymatic digestion. Flow cytometry was used to measure the purity of isolated cells. Immunofluorescence assay was performed to detect the location of ABCA1 and toll-like receptor 4 (TLR4). Reverse transcription PCR and western blotting analyses were used to examine ABCA1, TLR4 and inflammatory factor expression in primary cells. ELISA was used to detect cytokine secretions from the primary cells.

KEY FINDINGS

ABCA1 and TLR4 were mainly located in the cell nucleus and cytoplasm of feto-maternal interface cells. ABCA1 expression remained the highest in chorion cells, medium in decidual cells, and weakest in AMCs. Upregulated expression of ABCA1 decreased expression of TLR4 and the levels of pro-inflammatory factors, but increased cytoprotective factors in all cell types. In contrast, downregulated expression of ABCA1 increased the expression of TLR4 and pro-inflammatory factors, but decreased the levels of cytoprotective factors. Downregulated ABCA1 expression followed by decreased TLR4 expression using a small interference RNA (siRNA) induced reduction of interleukin (IL)-1β and tumor necrosis factor-α (TNF-α) in all cell types.

SIGNIFICANCE

ABCA1 at feto-maternal interface acts as an anti-inflammatory role by reducing the expression of TLR4 in uncomplicated pregnancies. ABCA1 might be a potential therapeutic target for preventing gestational diseases.

In vivo Assessment of Supra-Cervical Fetal Membrane by MRI 3D CISS: A Preliminary Study

In approximately 8% of term births and 33% of pre-term births, the fetal membrane (FM) ruptures before delivery. In vitro studies of FMs after delivery have suggested the series of events leading to rupture, but no in vivo studies have confirmed this model. In this study, we used a three-dimensional constructive interference in steady state (3D-CISS) sequence to examine the FM at the cervical internal os zone during pregnancy; 18 pregnant women with one to three longitudinal MRI scans were included in this study. In 14 women, the FM appeared normal and completely intact. In four women, we noted several FM abnormalities including cervical funneling, chorioamniotic separation, and chorion rupture. Our data support the in vitro model that the FM ruptures according to a sequence starting with the stretch of chorion and amnion, then the separation of amnion from chorion, next the rupture of chorion, and finally the rupture of amnion ruptures. These findings hold great promise to help to develop an in vivo magnetic resonance imaging marker that improves examination of the FMs.

The role of noninvasive diagnostic imaging in monitoring pregnancy and detecting patients at risk for preterm birth: a review of quantitative approaches

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. The ability to predict patients at risk for preterm birth remains a major health challenge. The currently available clinical diagnostics such as cervical length and fetal fibronectin may detect only up to 30% of patients who eventually experience a spontaneous preterm birth. This paper reviews ongoing efforts to improve the ability to conduct a risk assessment for preterm birth. In particular, this work focuses on quantitative methods of imaging using ultrasound-based techniques, magnetic resonance imaging, and optical imaging modalities. While ultrasound imaging is the major modality for preterm birth risk assessment, a summary of efforts to adopt other imaging modalities is also discussed to identify the technical and diagnostic limits associated with adopting them in clinical settings. We conclude the review by proposing a new approach using combined photoacoustic, ultrasound, and elastography as a potential means to better assess cervical tissue remodeling, and thus improve the detection of patients at-risk of PTB.

Prediction of Preterm Birth: Maternal Characteristics, Ultrasound Markers, and Biomarkers: An Updated Overview

There is not a single or combined screening method for preterm birth with high sensitivity which will truly identify the women at risk for preterm birth while also with high specificity to prevent unnecessary interventions and high treatment costs. Measurement of cervical length is the most cost-effective method that is used in clinical practice. Bedside tests have also been developed for detecting markers like fetal fibronectin, insulin-like growth factor binding protein-1 (IGFBP-1), interleukin-6, and placental alpha-macroglobulin-1. Taking the maternal history, health condition, and sociodemographical factors into consideration is recommended. Ultrasound markers apart from cervical length measurements as uterocervical angle and placental strain ratio are studied. Investigations on metabolomics, proteomics, and microRNA profiling have brought a new aspect on this subject. Maybe in the future, with clear identification of women at true risk for preterm birth, development of more effective preventive strategies will not be unfeasible.

Differential expression and methylation of integrin subunit alpha 11 and thrombospondin in the amnion of preterm birth

Objective

This study aimed to investigate the association between preterm birth and epigenetic mechanisms in the amnion.

Methods

We examined the association between differentially methylated regions (DMRs) and differentially expressed genes (DEG) using a cytosine-phosphate-guanine methylation array and whole-transcriptome sequencing from the amnion (preterm birth, n=5; full term, n=5). We enrolled 35 participants for mRNA expression analysis and pyrosequencing: 16 full-term and 19 preterm subjects. We compared the association of integrin subunit alpha 11 (ITGA11) and thrombospondin 2 (THBS2) gene methylation status with mRNA expression in the amnion.

Results

In the preterm birth group, methylation of ITGA11 and THBS2 genes was significantly lower (ITGA11 gene: 60.30% vs. 73.16%, P<0.05; THBS2 gene: 64.59% vs. 73.16%, P<0.05), and the expression of the genes was significantly higher than that in the full-term group (ITGA11 gene: 14.20 vs. 1.57, P<0.01; THBS2 gene: 1.18 vs. 10.34, P<0.05).

Conclusion

Methylation of the ITGA11 and THBS2 genes in the amnion was associated with preterm birth. Thus, ITGA11 and THBS2 gene methylation status in the amnion may be valuable in explaining the mechanism underlying preterm birth.

Oxidative stress induces p38MAPK-dependent senescence in the feto-maternal interface cells

OBJECTIVE

This study tested the mechanism of the oxidative stress (OS)-induced senescence pathway at the feto-maternal interface cells.

METHODS

Primary amnion mesenchymal cells (AMCs), chorion and decidual cells isolated from the placental membranes of women at normal term (not in labor) were exposed to OS-inducing cigarette smoke extract (CSE) for 48 h. Reactive oxygen species (ROS) was measured using 2'7'-dichlorodihydrofluorescein. Western blot analysis determined phosphorylated (P) p38MAPK and p53 expression. Senescence-associated β-Galactosidase (SA-β-Gal) and matrix metallopeptidase 9 (MMP9) histochemistry were used to measure senescence and inflammation respectively. Cotreatment of cells with the antioxidant, N-acetyl cysteine (NAC), or the p38MAPK inhibitor, SB203580 (SB), verified the activation specificity.

RESULTS

CSE increased ROS production from AMCs, chorion cells, and decidual cells (P < 0.05) compared to controls. Western blot analysis determined that CSE induced p38MAPK activation (P < 0.05) and cotreatment with NAC inhibited ROS production and p38MAPK activation (P < 0.05) in all cell types. CSE did not increase p53 phosphorylation in any of the cells; however, AMCs showed constitutive P-p53 expression. CSE increased senescence in AMCs and chorion cells compared to controls (P = 0.01 and P = 0.003, respectively); however, senescence was not observed in decidual cells. Senescence was significantly reduced following cotreatment with SB and NAC (AMCs; P = 0.01 and chorion; P = 0.009). CSE increased MMP9 in all cells that was reduced by NAC.

CONCLUSION

OS induced p38MAPK activation and inflammation in all cell types that was associated with senescence in fetal cells but not in maternal cells.

Reducing the number of obstetrical beds by challenging traditions

The aim of this commentary is to describe changes in women's care at an obstetric department that made it possible to reduce the number of beds from 40 to 29. Patient pathways were reviewed and revised using lean methodology. The mean length of stay was reduced from 70 to 59 h and the mean numbers of hospitalizations per woman from 1.26 to 1.20. At the organizational level, we introduced a Family Department, home management of newborns, home monitoring of the women with cardiotocography and blood samples, and intrapartum Group B Streptococcus-PCR. Additionally, an After Birth Clinic and network meetings for vulnerable women were established. In patient pathway, we reduced the hospitalization indicated by preterm premature rupture of membranes, preeclampsia and observation after birth laceration. According to National Patient Satisfaction surveys, there was no decrease in women's satisfaction after reducing the number of beds.

Quantification of bladder wall biomechanics during urodynamics: A methodologic investigation using ultrasound

Overactive bladder is often characterized by biomechanical changes in the bladder wall, but there is no established method to measure these changes in vivo. The goal of this study was to develop a novel method to determine detrusor wall biomechanical parameters during urodynamics through the incorporation of transabdominal ultrasound imaging. Individuals with overactive bladder (OAB) underwent ultrasound imaging during filling. The fill rate was 10% of the cystometric capacity per minute as determined by an initial fill. Transabdominal ultrasound images were captured in the midsagittal and transverse planes at 1min intervals. Using image data and Pves, detrusor wall tension, stress, and compliance were calculated. From each cross-sectional image, luminal and wall areas along with inner perimeters were measured. In the sagittal and transverse planes, wall tension was calculated as Pves∗luminal area, wall stress as tension/wall area, and strain as the change in perimeter normalized to the perimeter at 10% capacity. Elastic modulus was calculated as stress/strain in the medial-lateral and cranial-caudal directions. Patient-reported fullness sensation was continuously recorded. Data from five individuals with OAB showed that detrusor wall tension, volume, and strain had the highest correlations to continuous bladder sensation of all quantities measured. This study demonstrates how detrusor wall tension, stress, strain, and elastic modulus can be quantified by adding ultrasound imaging to standard urodynamics. This technique may be useful in diagnosing and better understanding the biomechanics involved in OAB and other bladder disorders.