Interventions to prevent spontaneous preterm birth in women with singleton pregnancy who are at high risk: systematic review and network meta-analysis

FIGO good practice recommendations on optimizing models of care for the prevention and mitigation of preterm birth

The global challenge of preterm birth persists with little or no progress being made to reduce its prevalence or mitigate its consequences, especially in low-resource settings where health systems are less well developed. Improved delivery of respectful person-centered care employing effective care models delivered by skilled healthcare professionals is essential for addressing these needs. These FIGO good practice recommendations provide an overview of the evidence regarding the effectiveness of the various care models for preventing and managing preterm birth across global contexts. We also highlight that continuity of care within existing, context-appropriate care models (such as midwifery-led care and group care), in primary as well as secondary care, is pivotal to delivering high quality care across the pregnancy continuum-prior to conception, through pregnancy and birth, and preparation for a subsequent pregnancy-to improve care to prevent and manage preterm birth.

Comparing cervical cerclage, pessary and vaginal progesterone for prevention of preterm birth in women with a short cervix (SuPPoRT): A multicentre randomised controlled trial

BACKGROUND

Cervical cerclage, cervical pessary, and vaginal progesterone have each been shown to reduce preterm birth (PTB) in high-risk women, but to our knowledge, there has been no randomised comparison of the 3 interventions. The SuPPoRT "Stitch, Pessary, or Progesterone Randomised Trial" was designed to compare the rate of PTB <37 weeks between each intervention in women who develop a short cervix in pregnancy.

METHODS AND FINDINGS

SuPPoRT was a multicentre, open label 3-arm randomised controlled trial designed to demonstrate equivalence (equivalence margin 20%) conducted from 1 July 2015 to 1 July 2021 in 19 obstetric units in the United Kingdom. Asymptomatic women with singleton pregnancies with transvaginal ultrasound cervical lengths measuring <25 mm between 14+0 and 23+6 weeks' gestation were eligible for randomisation (1:1:1) to receive either vaginal cervical cerclage (n = 128), cervical pessary (n = 126), or vaginal progesterone (n = 132). Minimisation variables were gestation at recruitment, body mass index (BMI), and risk factor for PTB. The primary outcome was PTB <37 weeks' gestation. Secondary outcomes included PTB <34 weeks', <30 weeks', and adverse perinatal outcome. Analysis was by intention to treat. A total of 386 pregnant women between 14+0 and 23+6 weeks' gestation with a cervical length <25 mm were randomised to one of the 3 interventions. Of these women, 67% were of white ethnicity, 18% black ethnicity, and 7.5% Asian ethnicity. Mean BMI was 25.6. Over 85% of women had prior risk factors for PTB; 39.1% had experienced a spontaneous PTB or midtrimester loss (>14 weeks gestation); and 45.8% had prior cervical surgery. Data from 381 women were available for outcome analysis. Using binary regression, randomised therapies (cerclage versus pessary versus vaginal progesterone) were found to have similar effects on the primary outcome PTB <37 weeks (39/127 versus 38/122 versus 32/132, p = 0.4, cerclage versus pessary risk difference (RD) -0.7% [-12.1 to 10.7], cerclage versus progesterone RD 6.2% [-5.0 to 17.0], and progesterone versus pessary RD -6.9% [-17.9 to 4.1]). Similarly, no difference was seen for PTB <34 and 30 weeks, nor adverse perinatal outcome. There were some differences in the mild side effect profile between interventions (vaginal discharge and bleeding) and women randomised to progesterone reported more severe abdominal pain. A small proportion of women did not receive the intervention as per protocol; however, per-protocol and as-treated analyses showed similar results. The main study limitation was that the trial was underpowered for neonatal outcomes and was stopped early due to the COVID-19 pandemic.

CONCLUSIONS

In this study, we found that for women who develop a short cervix, cerclage, pessary, and vaginal progesterone were equally efficacious at preventing PTB, as judged with a 20% equivalence margin. Commencing with any of the therapies would be reasonable clinical management. These results can be used as a counselling tool for clinicians when managing women with a short cervix.

TRIAL REGISTRATION

EU Clinical Trials register. EudraCT Number: 2015-000456-15, clinicaltrialsregister.eu., ISRCTN Registry: ISRCTN13364447, isrctn.com.

Cervical length measurement between 11 and 13 + 6 weeks of pregnancy: Comparison of maternal and ultrasonographic characteristics between term and preterm deliveries

OBJECTIVE

The aim of this study was to evaluate the maternal and ultrasonographic characteristics of pregnant women who underwent cervical length (CL) measurement by transvaginal ultrasound between 11 and 13 + 6 weeks of gestation and who delivered at term or preterm.

METHODS

A retrospective cohort study was carried out between March 2013 and December 2018 by analyzing ultrasound data of singleton pregnant women who underwent CL measurement by transvaginal ultrasound during the first trimester scan. CL was compared between the two groups (full-term and preterm birth [PB]) using Student's t-test.

RESULTS

A total of 5097 pregnant women were enrolled, of whom 5061 (99.3%) had term and 36 (0.7%) had PB < 34 weeks. CL measurements did not differ between the term and preterm groups (36.62 vs. 37.83 mm, p = 0.08). Maternal age showed a significant and linear association with CL (r = 0.034, p = 0.012) and CRL (r = 0.086, p < 0.001). Smoking status was associated with shorter CL (36.64 vs. 35.09 mm, p = 0.003). When we analyzed the CL of the pregnant women in the term and preterm groups, according to the gestational age cut-offs for prematurity (28, 30, 32, and 34 weeks), we found that there was no significant difference between the measurements in all groups (p > 0.05).

CONCLUSION

We observed no significant differences between CL measurements between 11 and 13 + 6 weeks in pregnant women who had preterm and term deliveries. Gestational age and CRL showed a significant and linear association with CL measurement.

Preventing Preterm Birth: Exploring Innovative Solutions

This review examines the complexities of preterm birth (PTB), emphasizes the pivotal role of inflammation in the pathogenesis of preterm labor, and assesses current available interventions. Antibiotics, progesterone analogs, mechanical approaches, nonsteroidal anti-inflammatory drugs, and nutritional supplementation demonstrate a limited efficacy. Tocolytic agents, targeting uterine activity and contractility, inadequately prevent PTB by neglecting to act on uteroplacental inflammation. Emerging therapies targeting toll-like receptors, chemokines, and interleukin receptors exhibit promise in mitigating inflammation and preventing PTB.

Longitudinal evaluation of cervical length and shear wave elastography in women with spontaneous preterm birth

OBJECTIVE

To evaluate longitudinal changes in cervical length (CL) and mean cervical shear wave elastography (CSWE) score in women with a singleton or twin pregnancy who undergo spontaneous preterm birth (sPTB) compared with those who deliver at term.

METHODS

This was a prospective longitudinal study of unselected women with a singleton or twin pregnancy attending a dedicated research clinic for screening for sPTB at four timepoints during pregnancy: 11 + 0 to 15 + 6 weeks, 16 + 0 to 20 + 6 weeks, 21 + 0 to 24 + 6 weeks and 28 + 0 to 32 + 6 weeks. At each visit, a transvaginal ultrasound scan was conducted to measure the CL and the CSWE scores in six regions of interest (ROI) (inner, middle and external parts of anterior and posterior cervical lips). The mean CSWE score from the six ROIs was calculated for analysis. Log10 transformation was applied to data to produce a Gaussian distribution prior to statistical analysis. A multilevel mixed-effects analysis was performed to compare longitudinally CL and CSWE between the sPTB and term-delivery groups.

RESULTS

The final cohort consisted of 1264 women, including 1143 singleton pregnancies, of which 57 (5.0%) were complicated by sPTB, and 121 twin pregnancies, of which 33 (27.3%) were complicated by sPTB. Compared to those who delivered at term, women with sPTB had a lower CL across gestation when controlling for history of cervical surgery, number of fetuses, gestational age (GA) at cervical assessment and the interaction between GA at cervical assessment and sPTB (P < 0.001). Specifically, CL in the sPTB group was significantly lower at 21 + 0 to 24 + 6 weeks (P = 0.039) and 28 + 0 to 32 + 6 weeks (P < 0.001). Twin pregnancies had significantly greater CL throughout pregnancy compared with singleton pregnancies (regression coefficient, 0.01864; P < 0.001). After adjusting for maternal age, weight, height, body mass index and GA at cervical assessment, CSWE score in the sPTB group was significantly lower compared with that in the term-delivery group across gestation (P = 0.013). However, on analysis of individual visits, CSWE score in the sPTB group was significantly lower than that in the term-delivery group only at 11 + 0 to 15 + 6 weeks (P = 0.036). There was no difference in CSWE score between singleton and twin pregnancies throughout gestation (regression coefficient, -0.00128; P = 0.937).

CONCLUSIONS

Women with sPTB have a shorter and softer cervix across gestation compared with those who deliver at term. A shorter cervix in the sPTB group is observed from the late second trimester onwards, while lower cervical stiffness in the sPTB group is observed primarily in the first trimester. CL is significantly lower in singleton pregnancies compared with twin pregnancies, while cervical stiffness does not differ between the two. Our findings indicate that the cervix tends to undergo a softening process prior to shortening in sPTB cases. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Use and Impact of Pessary, Cerclage, and Progesterone for the Secondary Prevention of Preterm Birth: Data from the German Neonatal Network

BACKGROUND

To evaluate the use and effect of cervical stitch cerclage, pessary, and progesterone on pregnancy outcome in mothers of very low birth weight infants (VLBWI) born<32 weeks of gestation in the German Neonatal Network (GNN).

METHODS

The GNN is a population-based cohort study enrolling VLBWI since 2009. We included 575 neonates from 424 mothers into our analysis, who were born between 2015 and 2019, after prenatal intervention with cerclage, pessary, progesterone or a combination between 20/0 to 25/0 weeks of gestation to prevent preterm birth. Median intervention-to-birth interval was the primary endpoint.

RESULTS

231 of 424 pregnant women had a cerclage only (54.5%), 76 women a pessary only (17.9%), and 27 were prescribed progesterone only (15.3%). The most common combination treatment (>1 intervention group) was cerclage plus progesterone (n=27), followed by cerclage plus pessary (n=13). The median intervention-to-birth interval for the whole cohort was 24 days (IQR 19.0 days). The earlier the intervention was started, the longer the intervention-to-birth interval lasted: When started at 20 weeks, the interval was 34 days in contrast to 11.5 days, when started at 25 weeks. The >1 group was born at a significantly higher median GA with 27.0 weeks (IQR 2.9 weeks) and a higher median birth weight of 980 g (IQR 394 g) accordingly.

CONCLUSION

We propose that the earliest possible start of intervention leads to the most efficient pregnancy prolongation.

Cervical length screening among low-risk women; relationship of body mass index on cervical length and risk of preterm birth

BACKGROUND

Preterm birth (PTB) contributes to nearly 11% of all deliveries in the world. The majority of spontaneous preterm birth (sPTB) remains unexplained. Risk factors include abnormal body mass index (BMI), short cervical length, comorbidities and many more. However, there is limited study on the association between body mass index, cervical length and preterm birth in Malaysia among low-risk women. Hence, we aim to examine the relationship between body mass index, cervical length and the risk of spontaneous preterm birth.

METHOD

In this prospective cohort study, pregnant women between 16 and 24 weeks who fulfilled the criteria were recruited. Women with history of preterm birth were excluded. Demographic and clinical data (age, BMI, ethnicity, education level and parity) were obtained. Cervical length was measured using transvaginal scan. Patients were then followed up till delivery to determine their delivery gestation and outcome of delivery.

RESULTS

Out of 153 women who participated in this study, 146 women had cervical length of more than 30 mm, six had cervical length between 25 mm and 30 mm and one had cervical length of 24 mm. There were nine (9) cases of sPTB, with all of them being late preterm with normal midtrimester cervical length. Almost half of them (44%) were overweight/obese. A significant association was found between age, cervical length, and parity compared to BMI. Nevertheless, no significant association was seen between the BMI and risk of sPTB.

CONCLUSION

This study demonstrates a higher BMI is associated with longer cervical length, but it is not necessarily protective against sPTB. Hence, we concluded there is a limited role in cervical length screening among low-risk women regardless of their BMI in predicting sPTB.

Nationwide status of progestogen treatment to prevent spontaneous preterm birth: A questionnaire survey for childbirth healthcare facilities in Japan

AIM

This study aimed to investigate the current status of progestogen treatment for pregnant women at a high risk for preterm birth (PTB) in childbirth healthcare facilities in Japan.

METHODS

A web-based nationwide questionnaire survey regarding progestogen use for prevention of PTB was conducted among childbirth healthcare facilities from 2019 to 2021.

RESULTS

Valid responses were obtained from 528 facilities (25.2% of those surveyed), including 155 tertiary perinatal facilities (making up 92.3% of all tertiary perinatal care facilities). In the survey period, progestogen treatment was implemented in 207 facilities (39.2%) for PTB prevention. Regarding types of progestogens, 17α-hydroxyprogesterone caproate was used in 170 facilities (82.1%), with a low dose (125 mg/week) administered in 62.9% of the facilities to comply with the regulations of the national health insurance system, although 250 mg/week is considered the best dose. Vaginal progesterone was used in 36 facilities (17.4%), although the cost of vaginal progesterone was not covered by health insurance. Of the facilities not administering progestogen treatment, approximately 40% expressed that vaginal progesterone would be their first choice for PTB prevention in daily practice if it would be covered by health insurance in the future.

CONCLUSIONS

Due to the current regulations of the Japanese health insurance system, 17α-hydroxyprogesterone caproate, rather than vaginal progesterone, was mainly used for PTB prevention. Despite global evidence supporting vaginal progesterone as the approach with the highest efficacy, only a limited number of facilities have utilized it due to the current drug use regulations in Japan.

Longitudinal Cervical Length Measurements and Spontaneous Preterm Birth in Singleton and Twin Pregnancies

Importance

Changes in cervical length in twin pregnancies exhibit various patterns, but it is unclear whether the mechanism underlying spontaneous preterm birth (sPTB) is consistent. The existence of detailed phenomena in singleton pregnancies is also unclear.

Objectives

To explore the different patterns in cervical length trajectories in singleton and twin pregnancies and to analyze whether the immunological mechanisms of sPTB are consistent among these cervical length patterns.

Design, Setting, and Participants

This cohort study recruited pregnant individuals who received antenatal care and delivered at Peking University Third Hospital in Beijing, China, between January 1, 2014, and December 31, 2022. Individuals with singleton and twin pregnancies were included.

Exposures

Cervical length measurements and white blood cell (WBC) indicators.

Main Outcomes and Measures

The primary outcome was sPTB. Longitudinal trajectory cluster analysis was used to identify patterns of changes in cervical length in singleton and twin pregnancies. A random-effects model with cubic spline was used to fit and compare the longitudinal trajectory of WBC indicators among early preterm birth, moderate to late preterm birth, and term birth.

Results

A total of 43 559 pregnant individuals were included; of these, 41 706 had singleton pregnancies (mean [SD)] maternal age, 33.0 [4.0] years) and 1853 had twin pregnancies (mean [SD] maternal age, 33.3 [3.6] years). Two distinct patterns of cervical length changes were observed in both singleton and twin pregnancies: shortened (21 366 singletons and 546 twins) and stable (20 340 singletons and 1307 twins). In singleton pregnancies, WBC count was associated with early sPTB in individuals with both shortened cervix (odds ratio [OR], 1.35; 95% CI, 1.00-1.82) and stable cervix (OR, 1.64; 95% CI, 1.07-2.50). However, for twin pregnancies, the association of WBC count (OR, 3.13; 95% CI, 1.58-6.18) with the risk of early sPTB was observed only in individuals with a shortened cervix.

Conclusions and Relevance

This study identified 2 distinct cervical length patterns: shortened and stable. These patterns revealed 2 preterm birth mechanisms in twin pregnancies, with the immunopathogenesis of sPTB found only in the shortened cervix pattern; in singleton pregnancies, maternal immune response was associated with a higher risk of sPTB regardless of a shortened or stable cervix.

Strategies for Safeguarding High-Risk Pregnancies From Preterm Birth: A Narrative Review

Preterm birth is the delivery of a live fetus before the 37th week of gestation. Preterm birth may stem from various factors, including premature rupture of membranes, spontaneous preterm labor, or medically induced circumstances. Premature delivery can result in serious and long-lasting difficulties even for infants who survive, as it is the leading cause of death for infants under five years old. Numerous nations have implemented initiatives to detect and track pregnant women who may give birth before their due date. Numerous therapies are available to protect these at-risk groups from the devastating effects of premature delivery, given the complex nature of preterm birth risk factors. Among the preventive measures, prophylactic progesterone appears to hold significant promise, while cervical cerclage proves effective in cases of cervical insufficiency. Conversely, pessaries show no discernible beneficial effects in reducing the risk of preterm birth. Regular antenatal visits are imperative for frequent patient evaluation and screening for potential risk factors. Adopting a healthy lifestyle can influence the risk of developing preeclampsia, with regular physical activity, a fiber-rich diet, and smoking cessation serving to mitigate the risk of preterm birth. The efficacy of bed rest in preventing preterm birth remains inconclusive due to insufficient evidence. This study aims to explore various preventive strategies for averting premature birth in high-risk women.

Maternal cobalt concentration and risk of spontaneous preterm birth: the role of fasting blood glucose and lipid profiles

Introduction

Spontaneous preterm birth (SPB) is a significant cause of neonatal mortality, yet its etiology remains unclear. Cobalt, an essential trace element, might be a risk factor for SPB. This study aims to investigate the relationship between maternal serum cobalt concentration and SPB, and to clarify the role of blood lipids and fasting blood glucose (FBG) in this relationship.

Methods

We conducted a nested case-control study within the Beijing Birth Cohort Study. Serum samples were obtained from 222 pregnant women with SPB and 224 controls during the first (7-13 weeks of pregnancy) and third trimesters (32-42 weeks of pregnancy). Serum cobalt concentration was determined using inductively coupled plasma mass spectrometry (ICP-MS). Fasting blood glucose and lipids levels were detected using a fully automated biochemical immunoassay instrument. Logistic regression models and linear regression models were established to explore the association between serum cobalt concentration and the risk of SPB in pregnant women, and to test the mediating effect of fasting blood glucose (FBG) and lipids.

Results

We found that the serum cobalt concentration in mothers with SPB and controls was similar in the first trimester, with values of 0.79 (0.58-1.10) ng/mL and 0.75 (0.51-1.07) ng/mL, respectively. However, in the third trimester, the cobalt concentration increased to 0.88 (0.59-1.14) ng/mL and 0.84 (0.52-1.19) ng/mL, respectively. In the logistic regression model, when considering the third trimester of pregnancy, after adjusting for ethnicity, pre-pregnancy body mass index (BMI), maternal age, education, income, and parity, it was observed that the medium level of cobalt concentration (0.63-1.07 ng/ml) had a negative correlation with the risk of SPB. The odds ratio (OR) was 0.56, with a 95% confidence interval of 0.34-0.90 ng/mL and a p-value of 0.02. This suggests that cobalt in this concentration range played a protective role against SPB. Additionally, it was found that FBG in the third trimester of pregnancy had a partial intermediary role, accounting for 9.12% of the association. However, no relationship between cobalt and SPB risk was found in the first trimester.

Conclusion

During the third trimester, intermediate levels of maternal cobalt appear to offer protection against SPB, with FBG playing a partial mediating role. To further clarify the optimal cobalt concentrations during pregnancy for different populations, a multi-center study with a larger sample size is necessary. Additionally, exploring the specific mechanism of FBG's mediating role could provide valuable insights for improving the prevention of SPB.

Relationship of Lactobacillus Vaginal Microbiota Changes and the Risk of Preterm Birth: A Systematic Review and Meta-Analysis

Objective: With a global incidence of more than 10%, preterm birth (PTB) remains a significant concern. The vaginal microbiome strongly influences the well-being of the female reproductive tract. This study examines the correlation between changes in Lactobacillus vaginal microbiota and the PTB risk. Materials and Methods: A thorough search of PubMed, Web of Science, Cochrane Library, and EMBASE was conducted to locate studies that examined the association between changes in Lactobacillus vaginal microbiota and the risk of PTB from January 1, 2010, to January 30, 2023. The risk of PTB was determined by calculating odds ratios (ORs) with 95% confidence intervals (CIs). Results: In our analysis, there were 11 studies with 1577 pregnant women. The findings revealed a significant negative correlation between higher Lactobacillus abundance and the PTB risk (OR = 0.49, 95% CI: 0.29-0.84, p = 0.009 < 0.05). Similarly, the four individual dominant species, Lactobacillus crispatus (OR = 0.3, 95% CI: 0.14-0.67, p = 0.003 < 0.05), Lactobacillus gasseri (OR = 0.34, 95% CI: 0.17-0.69, p = 0.003 < 0.05), Lactobacillus iners (OR = 0.68, 95% CI: 0.49-0.93, p = 0.016 < 0.05), and Lactobacillus jensenii (OR = 0.43, 95% CI: 0.21-0.89, p = 0.024 < 0.05), were also negatively associated with the PTB risk. The risk of Lactobacillus for PTB was significant in both America (OR = 0.67; 95% CI: 0.50-0.92) and Asia (OR = 0.20; 95% CI: 0.09-0.47), whereas no significant risk was found in Europe (OR = 0.49; 95% CI: 0.11-2.15). Conclusions: Our study demonstrated that the abundance of Lactobacillus and the four dominant individual species (L. crispatus, L. jensenii, L. iners, and L. gasseri) were significantly and negatively associated with the PTB risk.

Predicting preterm birth using auto-ML frameworks: a large observational study using electronic inpatient discharge data

Background

To develop and compare different AutoML frameworks and machine learning models to predict premature birth.

Methods

The study used a large electronic medical record database to include 715,962 participants who had the principal diagnosis code of childbirth. Three Automatic Machine Learning (AutoML) were used to construct machine learning models including tree-based models, ensembled models, and deep neural networks on the training sample (N = 536,971). The area under the curve (AUC) and training times were used to assess the performance of the prediction models, and feature importance was computed via permutation-shuffling.

Results

The H2O AutoML framework had the highest median AUC of 0.846, followed by AutoGluon (median AUC: 0.840) and Auto-sklearn (median AUC: 0.820), and the median training time was the lowest for H2O AutoML (0.14 min), followed by AutoGluon (0.16 min) and Auto-sklearn (4.33 min). Among different types of machine learning models, the Gradient Boosting Machines (GBM) or Extreme Gradient Boosting (XGBoost), stacked ensemble, and random forrest models had better predictive performance, with median AUC scores being 0.846, 0.846, and 0.842, respectively. Important features related to preterm birth included premature rupture of membrane (PROM), incompetent cervix, occupation, and preeclampsia.

Conclusions

Our study highlights the potential of machine learning models in predicting the risk of preterm birth using readily available electronic medical record data, which have significant implications for improving prenatal care and outcomes.

Expert consensus on novel medicines to prevent preterm birth and manage preterm labour: Target product profiles

OBJECTIVE

To develop target product profiles (TPPs) for new medicines for preterm birth prevention and preterm labour management that address the real-world need of women and healthcare providers, informed by views and agreement amongst globally diverse stakeholders.

DESIGN

Mixed methods.

SETTING

Global (with a focus on low- and middle-income countries, LMICs).

SAMPLE

Global stakeholders with diverse expertise in preterm labour/birth and drug development.

METHODS

Following an initial literature review, diverse stakeholders were invited to participate in an online international survey and in-depth interviews. The level of stakeholder agreement with TPPs was assessed, and findings from interviews were synthesised to inform the final TPPs.

MAIN OUTCOMES MEASURES

Level of stakeholder agreement on the minimum and preferred requirements for preterm labour/birth medicines.

RESULTS

We performed 21 interviews. Interview participants demonstrated strong agreement on room temperature stability, no additional drug-specific clinical monitoring, and affordability in LMICs being the minimal acceptable requirements. Points of discussion were raised around the target population. Survey respondents included clinicians, researchers, funding agency staff, international public organisation staff, programme implementers, policymakers, representatives of consumer advocacy organisations and other relevant stakeholders from maternal health systems. Survey results indicated strong agreement amongst stakeholders, with only one variable in each TPP not reaching consensus (i.e. 25% disagree or strongly disagree).

CONCLUSIONS

There is strong consensus within the preterm labour/birth community on the characteristics that new medicines for preterm birth prevention and preterm labour management must achieve. These TPPs provide necessary guidance to evaluate new candidates and their potential for implementation in a range of settings.

Prevention of spontaneous preterm delivery – an update on where we are today

Spontaneous preterm birth (delivery before 37 completed weeks) is the single most important cause of perinatal morbidity and mortality. The rate is increasing world-wide with a great disparity between low, middle and high income countries. It has been estimated that the cost of neonatal care for preterm babies is more than 4 times that of a term neonate admitted into the neonatal care. Furthermore, there are high costs associated with long-term morbidity in those who survive the neonatal period. Interventions to stop delivery once preterm labor starts are largely ineffective hence the best approach to reducing the rate and consequences is prevention. This is either primary (reducing or minimizing factors associated with preterm birth prior to and during pregnancy) or secondary - identification and amelioration (if possible) of factors in pregnancy that are associated with preterm labor. In the first category are optimizing maternal weight, promoting healthy nutrition, smoking cessation, birth spacing, avoidance of adolescent pregnancies and screening for and controlling various medical disorders as well as infections prior to pregnancy. Strategies in pregnancy, include early booking for prenatal care, screening and managing medical disorders and their complications, and identifying predisposing factors to preterm labor such as shortening of the cervix and timely instituting progesterone prophylaxis or cervical cerclage where appropriate. The use of biomarkers such as oncofetal fibronectin, placental alpha-macroglobulin-1 and IGFBP-1 where cervical screening is not available or to diagnosis PPROM would identify those that require close monitoring and allow the institution of antibiotics especially where infection is considered a predisposing factor. Irrespective of the approach to prevention, timing the administration of corticosteroids and where necessary tocolysis and magnesium sulfate are associated with an improved outcome. The role of genetics, infections and probiotics and how these emerging dimensions help in the diagnosis of preterm birth and consequently prevention are exciting and hopefully may identify sub-populations for targeted strategies.

Association between pre-pregnancy body mass index and the risk of preterm birth: a mediating effect of hypertensive disorders of pregnancy

OBJECTIVE

We aim to explore the mediating effect of hypertensive disorders of pregnancy (HDP) on the relationship between pre-pregnancy body mass index (BMI) and the risk of preterm birth (PTB) in women with singleton live births.

METHODS

Demographic and clinical data of 3,249,159 women with singleton live births were extracted from the National Vital Statistics System (NVSS) database in this retrospective cohort study. The associations between pre-pregnancy BMI and HDP, HDP, and PTB, and pre-pregnancy BMI and PTB were evaluated using univariate and multivariate logistic regression analyses, with odds ratios (ORs) and 95% confidence intervals (CIs). Structural equation modeling (SEM) was used to explore the mediating effect of HDP on the relationship between pre-pregnancy BMI and PTB.

RESULTS

In total, 324,627 women (9.99%) had PTB. After adjustment for covariables, there were significant associations between pre-pregnancy BMI and HDP [OR = 2.07, 95% CI: 2.05-2.09)], HDP and PTB [OR = 2.54, 95% CI: (2.52-2.57)], and pre-pregnancy BMI and PTB [OR = 1.03, 95% CI: 1.02-1.03)]. The effect of pre-pregnancy BMI on PTB was significantly mediated by HDP with a mediation proportion of 63.62%, especially in women of different ages and having gestational diabetes mellitus (GDM) or not.

CONCLUSION

HDP may play a mediating role in the effect of pre-pregnancy BMI on PTB risk. Women preparing for pregnancy should pay close attention to BMI, and pregnant women should monitor and develop interventions for HDP to reduce the risk of PTB.

A cross-sectional survey of women's views and preferences for preterm birth screening and treatment

OBJECTIVES

Primary outcomes were to determine; 1) the desire for more patient information from healthcare professionals on preterm birth (PTB) prevention 2) the desire for PTB screening surveillance or participation in research or 3) the acceptability of transvaginal ultrasound (TVUS) or vaginal examinations to predict spontaneous PTB.

METHODS

A 19-question, piloted, self-administered survey was completed by unselected pregnant women in a tertiary maternity hospital in Dublin, Ireland. Data was collected to include maternal socio-demographics, past obstetric history, and current pregnancy details, in addition to views and preferences on PTB screening and preventative treatments. Statistical analysis to include binary and multinomial regression was performed by IBM SPSS Statistics for Windows (Version 29.0).

RESULTS

277 women completed the study survey. 9.4% of women had attended the preterm birth surveillance clinic (PSC). 75.1% of respondents indicated a preference for more information from healthcare professionals about PTB. 65% reported that TVUS and vaginal examinations were acceptable in pregnancy. The acceptability of antenatal examinations was significantly influenced by ethnicity; white European (OR 2.58, CI 1.12-5.95, p = 0.003) and Asian (OR 3.39, CI 1.18-9.67, p = 0.02). Discomfort (25.3%) and vaginal bleeding (11.9%) were the most frequently reported concerns about TVUS. 95.7% of unselected women indicated that they would accept treatment to prevent PTB. Vaginal progesterone (53.8%) was preferred treatment compared to cervical cerclage (15.9%) or cervical pessary (16.6%). 55.6% of respondents stated they attend or wish to attend for additional appointments or research opportunities for PTB screening. Women with a previous PTB or second trimester miscarriage were more likely to attend or wish to attend for PTB screening (OR 3.23, CI 1.34-7.79, p = 0.009).

CONCLUSION

PTB is an important healthcare priority for pregnant women in Ireland. However, women require more information, counselling and reassurance about the utility and safety of TVUS in PSCs.

Prenatal PM2.5 exposure increases the risk of adverse pregnancy outcomes: evidence from meta-analysis of cohort studies

Adverse pregnancy outcomes (APOs) are a significant cause of fetal death. A wide range of maternal psychological, social, and environmental factors may contribute to these outcomes. Mounting epidemiological studies have indicated that PM2.5 may result in these unfavorable consequences. Previously published meta-analyses have been updated and extended. Cohort studies were searched from three databases (up to July 24, 2023), and their quality was assessed by Newcastle-Ottawa Scale (NOS). Publication bias was examined by Egger's test and funnel plot. Despite a large number of studies showing similar results, the inconsistencies between these findings require careful generalization before concluding. This meta-analysis included 67 cohort studies from 20 countries, and the findings revealed that maternal PM2.5 exposure and five APOs were correlated significantly throughout pregnancy: preterm birth (PTB) (RR = 1.05; 95% CI: 1.03, 1.07); low birth weight (LBW) (RR = 1.02; 95% CI: 1.01, 1.04); small for gestational age (SGA) (RR = 1.03; 95% CI: 1.01, 1.04); stillbirth (RR = 1.24; 95% CI: 1.06, 1.45); and change in birthweight (weight change = -6.82 g; 95% CI: -11.39, -2.25). A positive association was found between APOs and PM2.5 exposure in this meta-analysis, and the degree of increased risk of APOs varied due to different gestation periods. Therefore, it is necessary to protect pregnant women at specific times.

Bioengineering and the cervix: The past, current, and future for addressing preterm birth

The uterine cervix plays two important but opposing roles during pregnancy - as a mechanical barrier that maintains the fetus for nine months and as a compliant structure that dilates to allow for the delivery of a baby. In some pregnancies, however, the cervix softens and dilates prematurely, leading to preterm birth. Bioengineers have addressed and continue to address the lack of reduction in preterm birth rates by developing novel technologies to diagnose, prevent, and understand premature cervical remodeling. This article highlights these existing and emerging technologies and concludes with open areas of research related to the cervix and preterm birth that bioengineers are currently well-positioned to address.

Reassessing Preterm Birth Prevention After the Withdrawal of 17-α Hydroxyprogesterone Caproate

The U.S. Food and Drug Administration has recently withdrawn approval for 17-α hydroxyprogesterone caproate for prevention of recurrent preterm birth, and recent studies have called into question benefits of the pessary in the setting of a short cervix. Obstetric health care professionals are once again left with limited remaining options for preterm birth prevention. This narrative review summarizes the best current evidence on the use of vaginal progesterone, low-dose aspirin, and cerclage for the prevention of preterm birth; attempts to distill possible lessons learned from studies of progesterone and pessary, as well as their implementation into practice; and highlights areas where inroads into preterm birth prevention may be possible outside of the progesterone-aspirin-cerclage paradigm.

A systematic review of prediction models for spontaneous preterm birth in singleton asymptomatic pregnant women with risk factors

Backgrounds

Spontaneous preterm birth (SPB) is a global problem. Early screening, identification, and prevention in asymptomatic pregnant women with risk factors for preterm birth can help reduce the incidence and mortality of preterm births. Therefore, this study systematically reviewed prediction models for spontaneous preterm birth, summarised the model characteristics, and appraised their quality to identify the best-performing prediction model for clinical decision-making.

Methods

PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine disc, VIP Database, and Wanfang Data were searched up to September 27, 2021. Prediction models for spontaneous preterm births in singleton asymptomatic pregnant women with risk factors were eligible for inclusion. Six independent reviewers selected the eligible studies and extracted data from the prediction models. The findings were summarised using descriptive statistics and visual plots.

Results

Twelve studies with twelve developmental models were included. Discriminative performance was reported in 11 studies, with an Area Under the Curve (AUC) ranging from 0.75 to 0.95. The AUCs of the seven models were greater than 0.85. Cervical length (CL) is the most commonly used predictor of spontaneous preterm birth. A total of 91.7% of the studies had a high risk of bias in the analysis domain, mainly because of the small sample size and lack of adjustment for overfitting.

Conclusion

The accuracy of the models for spontaneous preterm births in singleton asymptomatic women with risk factors was good. However, these models are not widely used in clinical practice because they lack replicability and transparency. Future studies should transparently report methodological details and consider more meaningful predictors with new progress in research on preterm birth.

How to screen the cervix and reduce the risk of spontaneous preterm birth in asymptomatic women without a prior preterm birth

Preterm birth (PTB) is a leading cause of perinatal morbidity and mortality globally. PTB rates have increased in South Korea despite reduction in birth rates. A history of PTB is a strong predictor of subsequent PTB and screening of cervical length between 16 0/7 weeks and 24 0/7 weeks of gestation is recommended in women with a singleton pregnancy and a prior spontaneous PTB. However, the prediction and prevention of spontaneous PTBs in women without a prior PTB remain a matter of debate. The scope of this review article comprises cervical screening and prevention strategies for PTB in asymptomatic women without a prior PTB, based on recent evidence and guidelines.

Fat Intake and Fat Quality in Pregnant and Lactating Women, Infants, Children, and Adolescents and Related Health Outcomes: A Scoping Review of Systematic Reviews of Prospective Studies

INTRODUCTION

Dietary fat intake during pregnancy and childhood is important for health. However, several health aspects are inconclusive.

METHODS

We systematically searched Medline, Cochrane Library, and Epistemonikos for systematic reviews (SRs) of randomized controlled trials (RCTs) and/or prospective cohort studies published from January 01, 2015, to December 31, 2019, assessing the association of dietary fat intake (including dietary supplements) during pregnancy and across childhood with pregnancy, perinatal, and child health outcomes.

RESULTS

Thirty-one SRs, mainly of RCTs, were included. Omega-3 fatty acids supplementation during pregnancy reduced the risk of early preterm birth, and in some SRs also any preterm birth, increased gestation length and birth weight, but mostly was not associated with other pregnancy/perinatal outcomes. Pre- and postnatal polyunsaturated fatty acids (PUFAs) intake was not consistently associated with growth, neurological, visual and cognitive outcomes, allergic diseases, cardiovascular, and metabolic health in childhood. Reduced saturated fatty acids (SFAs) intake and its replacement with PUFA/monounsaturated fatty acids had favourable effects on blood pressure and blood lipids in children. No apparent effects of total or trans fat on health outcomes across target groups were observed.

CONCLUSION

Omega-3 PUFA supplementation during pregnancy and SFA intake reduction in childhood require further consideration in dietary recommendations targeting these populations.

Peripartum Maternal Admission to the Intensive Care Unit: An Observational Study over a 15-Year Period at a Tertiary Center in Austria

Peripartum maternal admission to the intensive care unit is challenging for anesthesiologists, obstetricians, and all personnel involved. An understanding of altered maternal physiology, fetal considerations, and acute peripartum emergencies is required to ensure adequate maternal and neonatal outcomes. In this study, we analyzed data of peripartum maternal admissions to the intensive care unit at our large tertiary referral center in order to define trends and changes over time. This study retrospectively analyzed maternal morbidity, admission diagnoses, treatments, and outcomes of women with peripartum admission to the intensive care unit at our tertiary care center over a 15-year period. We found that patient characteristics and admission diagnoses remained remarkably consistent over the observational period; however, there was a significant increase in postpartum hemorrhage (r = 0.200, p < 0.001) and cesarean hysterectomy (r = 0.117, p = 0.027) over time. Moreover, we found a reduction in preterm births (r = -0.154, p = 0.004) and a decreased peripartum neonatal intensive care unit admission rate (r = -0.153, p = 0.006) among women who were transferred to the intensive care unit. Based on our long-term observational data, there is consistent need for intensive care in obstetrics due to a small number of different etiologies. Specialized training for the predominant diagnoses involved as well as multidisciplinary care of the affected patients are both warranted.

Unraveling the Efficacy of Therapeutic Interventions for Short Cervix: Insights from a Retrospective Study for Improved Clinical Management

Background and Objectives: Preterm birth (PTB) is associated with important neonatal mortality and morbidity. The aim of this study was to retrospectively evaluate the average treatment effects on the treated and the efficacity of various therapeutic interventions for PTB in a cohort of patients with singleton pregnancies and short cervical lengths. Materials and Methods: This observational retrospective study included 1146 singleton pregnancies at risk of PTB that were segregated into the following groups: intravaginal progesterone (group 1), Arabin pessary (group 2), McDonald cerclage (group 3), intravaginal progesterone and Arabin pessary (group 4), and intravaginal progesterone and cerclage (group 5). Their treatment effects were evaluated and compared. Results: All evaluated therapeutic interventions significantly reduced the occurrence of late and early preterm births. The risk of late and early PTB was lowered for those pregnant patients who received progesterone and pessaries or progesterone and cerclage in comparison with those who received only progesterone. The extremely PTB risk of occurrence was significantly lowered only by the administration of progesterone in association with cervical cerclage in comparison with progesterone monotherapy. Conclusions: The combined therapeutic interventions had the highest efficacy in preventing preterm birth. An individualized evaluation is needed to establish the best therapeutic approach in particular cases.

County-Level Maternal Vulnerability and Preterm Birth in the US

Importance

Appreciation for the effects of neighborhood conditions and community factors on perinatal health is increasing. However, community-level indices specific to maternal health and associations with preterm birth (PTB) have not been assessed.

Objective

To examine the association of the Maternal Vulnerability Index (MVI), a novel county-level index designed to quantify maternal vulnerability to adverse health outcomes, with PTB.

Design, Setting, and Participants

This retrospective cohort study used US Vital Statistics data from January 1 to December 31, 2018. Participants included 3 659 099 singleton births at 22 plus 0/7 to 44 plus 6/7 weeks of gestation born in the US. Analyses were conducted from December 1, 2021, through March 31, 2023.

Exposure

The MVI, a composite measure of 43 area-level indicators, categorized into 6 themes reflecting physical, social, and health care landscapes. Overall MVI and theme were stratified by quintile (very low to very high) by maternal county of residence.

Main Outcomes and Measures

The primary outcome was PTB (gestational age <37 weeks). Secondary outcomes were PTB categories: extreme (gestational age ≤28 weeks), very (gestational age 29-31 weeks), moderate (gestational age 32-33 weeks), and late (gestational age 34-36 weeks). Multivariable logistic regression quantified associations of MVI, overall and by theme, with PTB, overall and by PTB category.

Results

Among 3 659 099 births, 298 847 (8.2%) were preterm (male, 51.1%; female, 48.9%). Maternal race and ethnicity included 0.8% American Indian or Alaska Native, 6.8% Asian or Pacific Islander, 23.6% Hispanic, 14.5% non-Hispanic Black, 52.1% non-Hispanic White, and 2.2% with more than 1 race. Compared with full-term births, MVI was higher for PTBs across all themes. Very high MVI was associated with increased PTB in unadjusted (odds ratio [OR], 1.50 [95% CI, 1.45-1.56]) and adjusted (OR, 1.07 [95% CI, 1.01-1.13]) analyses. In adjusted analyses of PTB categories, MVI had the largest association with extreme PTB (adjusted OR, 1.18 [95% CI, 1.07-1.29]). Higher MVI in the themes of physical health, mental health and substance abuse, and general health care remained associated with PTB overall in adjusted models. While the physical health and socioeconomic determinant themes were associated with extreme PTB, physical health, mental health and substance abuse, and general health care themes were associated with late PTB.

Conclusions and Relevance

The findings of this cohort study suggest that MVI was associated with PTB even after adjustment for individual-level confounders. The MVI is a useful measure for county-level PTB risk that may have policy implications for counties working to lower preterm rates and improve perinatal outcomes.

The clinical utility of ongoing sonographic cervix length surveillance in pregnancies prescribed vaginal progesterone therapy

BACKGROUND

Vaginal progesterone therapy significantly reduces preterm birth (PTB) rates in those high-risk pregnancies with a sonographic short cervix (≤25 mm) and/or a history of spontaneous PTB. Cervical length (CL) is routinely measured at the midtrimester morphology scan; however, CL surveillance thereafter is not currently recommended. Progesterone's precise mechanism of action remains unknown, though if it indeed influences CL, shortening after treatment initiation could indicate therapeutic failure and risk of PTB.

AIMS

The aim was to explore the utility of serial transvaginal ultrasound (TVU) measurement of CL at 16, 19 and 22 weeks for predicting PTB in high-risk pregnancies prescribed progesterone therapy.

METHODS

A retrospective cohort study was conducted involving women who attended the King Edward Memorial Hospital PTB Prevention Clinic from 2015 to 2019 and were prescribed progesterone therapy. CL was measured at 16, 19 and 22 weeks by TVU. CL change across three time points was assessed using linear mixed models; then relationships between CL change between 16-19 and 19-22 weeks and PTB were analysed using logistic regression models.

RESULTS

Term birth was most likely when CL did not decrease across both time periods. The addition of 16-19 week decrease in CL to a model, including CL at 19 weeks alone, for predicting PTB increased sensitivity from 43.2 to 56.3%, specificity from 73.2 to 77.4%, and overall accuracy from 61.7 to 70.2%.

CONCLUSION

For high-risk women prescribed vaginal progesterone therapy, serial measurement of the cervix at 16 and 19 weeks improves clinical ability to predict PTB from current recommendations of 19-week measurement alone.

Nanomedicine strategies to improve therapeutic agents for the prevention and treatment of preterm birth and future directions

The World Health Organisation (WHO) estimates 15 million babies worldwide are born preterm each year, with 1 million infant mortalities and long-term morbidity in survivors. Whilst the past 40 years have provided some understanding in the causes of preterm birth, along with development of a range of therapeutic options, notably prophylactic use of progesterone or uterine contraction suppressants (tocolytics), the number of preterm births continues to rise. Existing therapeutics used to control uterine contractions are restricted in their clinical use due to pharmacological drawbacks such as poor potency, transfer of drugs to the fetus across the placenta and maternal side effects from activity in other maternal systems. This review focuses on addressing the urgent need for the development of alternative therapeutic systems with improved efficacy and safety for the treatment of preterm birth. We discuss the application of nanomedicine as a viable opportunity to engineer pre-existing tocolytic agents and progestogens into nanoformulations, to improve their efficacy and address current drawbacks to their use. We review different nanomedicines including liposomes, lipid-based carriers, polymers and nanosuspensions highlighting where possible, where these technologies have already been exploited e.g. liposomes, and their significance in improving the properties of pre-existing therapeutic agents within the field of obstetrics. We also highlight where active pharmaceutical agents (APIs) with tocolytic properties have been used for other clinical indications and how these could inform the design of future therapeutics or be repurposed to diversify their application such as for use in preterm birth. Finally we outline and discuss the future challenges.

Progesterone, cerclage, pessary, or acetylsalicylic acid for prevention of preterm birth in singleton and multifetal pregnancies - A systematic review and meta-analyses

Background

Preterm birth is the leading cause of childhood mortality and morbidity. We aimed to provide a comprehensive systematic review on randomized controlled trials (RCTs) on progesterone, cerclage, pessary, and acetylsalicylic acid (ASA) to prevent preterm birth in asymptomatic women with singleton pregnancies defined as risk of preterm birth and multifetal pregnancies.

Methods

Six databases (including PubMed, Embase, Medline, the Cochrane Library) were searched up to February 2022. RCTs published in English or Scandinavian languages were included through a consensus process. Abstracts and duplicates were excluded. The trials were critically appraised by pairs of reviewers. The Cochrane risk-of-bias tool was used for risk of bias assessment. Predefined outcomes including preterm birth, perinatal/neonatal/maternal mortality and morbidity, were pooled in meta-analyses using RevMan 5.4, stratified for high and low risk of bias trials. The certainty of evidence was assessed using the GRADE approach. The systematic review followed the PRISMA guideline.

Results

The search identified 2,309 articles, of which 87 were included in the assessment: 71 original RCTs and 16 secondary publications with 23,886 women and 32,893 offspring. Conclusions were based solely on trials with low risk of bias (n = 50).Singleton pregnancies: Progesterone compared with placebo, reduced the risk of preterm birth <37 gestational weeks: 26.8% vs. 30.2% (Risk Ratio [RR] 0.82 [95% Confidence Interval [CI] 0.71 to 0.95]) (high certainty of evidence, 14 trials) thereby reducing neonatal mortality and respiratory distress syndrome. Cerclage probably reduced the risk of preterm birth <37 gestational weeks: 29.0% vs. 37.6% (RR 0.78 [95% CI 0.69 to 0.88]) (moderate certainty of evidence, four open trials). In addition, perinatal mortality may be reduced by cerclage. Pessary did not demonstrate any overall effect. ASA did not affect any outcome, but evidence was based on one underpowered study.Multifetal pregnancies: The effect of progesterone, cerclage, or pessary was minimal, if any. No study supported improved long-term outcome of the children.

Conclusion

Progesterone and probably also cerclage have a protective effect against preterm birth in asymptomatic women with a singleton pregnancy at risk of preterm birth. Further trials of ASA are needed. Prevention of preterm birth requires screening programs to identify women at risk of preterm birth.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021234946].

Pharmacological Interventions in Labor and Delivery

While there is not a wide range of pregnancy-specific drugs, there are some very specific high-risk areas of obstetric care for which unique pharmacological approaches have been established. In preterm birth, labor induction and augmentation, and the management of postpartum hemorrhage, these pharmacological approaches have become the bedrock in managing some of the most common and problematic areas of antenatal and intrapartum care. In this review, we summarize the existing established and emerging evidence that supports and broadens these pharmacological approaches to obstetric management and its impact on clinical practice. It is clear that existing therapeutics are limited. They have largely been developed from our knowledge of the physiology of the myometrium and act on hormonal receptors and their signaling pathways or on ion channels influencing excitability. Newer drugs in development are mostly refinements of these two approaches, but novel agents from plants and improved formulations are also discussed.

How are hospitals in England caring for women at risk of preterm birth in 2021? The influence of national guidance on preterm birth care in England: a national questionnaire

BACKGROUND

National guidance (Saving Babies Lives Care Bundle Version 2 (SBLCBv2) Element 5) was published in 2019, with the aim to standardise preterm care in England. We plan to identify how many preterm birth surveillance clinics there are in England, and to define current national management in caring for women who are both asymptomatic and high-risk of preterm birth, and who arrive symptomatically in threatened preterm labour, to assist preterm management both nationally and internationally.

METHODS

An online survey comprising of 27 questions was sent to all maternity units in England between February 2021 to July 2021.

RESULTS

Data was obtained from 96 units. Quantitative analysis and free text analysis was then undertaken. We identified 78 preterm birth surveillance clinics in England, an increase from 30 preterm clinics in 2017. This is a staggering 160% increase in 4 years. SBLCBv2 has had a considerable impact in increasing preterm birth surveillance clinic services, with the majority (61%) of sites reporting that the NHS England publication influenced their unit in setting up their clinic. Variations exist at every step of the preterm pathway, such as deciding which risk factors warrant referral, distinguishing within particular risk factors, and offering screening tests and treatment options.

CONCLUSIONS

While variations in care still do persist, hospitals have done well to increase preterm surveillance clinics, under the difficult circumstances of the COVID pandemic and many without specific additional funding.

Associations of circulation levels of cytokines with birthweight, preterm birth, spontaneous miscarriages, and stillbirth: A Mendelian randomization analysis

Background: The association between immune imbalances and adverse pregnancy outcomes has been extensive investigated by observational studies, but remain unclear. Thus, this study aimed to establish the causality of the circulation levels of cytokines on adverse pregnancy outcomes, such as offspring's birthweight (BW), preterm birth (PTB), spontaneous miscarriage (SM), and stillbirth (SB). Methods: Two-sample Mendelian randomization (MR) analysis was employed to investigate potential causal relations between 41 cytokines and pregnancy outcomes on the basis of previously published GWAS datasets. Multivariable MR (MVMR) analysis was implemented to investigate the effect of the composition of cytokine networks on the pregnancy outcomes. Potential risk factors were further estimated to explore the potential mediators. Results: Genetic correlation analysis based on large GWAS data sources revealed that genetically predicted MIP1b (β = -0.027, S.E. = 0.010, p = 0.009) and MCSF (β = -0.024, S.E. = 0.011, p = 0.029) were associated with reduced offspring's BW, MCP1 (OR: 0.90, 95% CI: 0.83-0.97, p = 0.007) was associated with reduced SM risk, SCF (β = -0.014, S.E. = 0.005, p = 0.012) associated with decreased number of SB in MVMR. The univariable MR showed that GROa (OR: 0.92, 95% CI: 0.87-0.97, p = 0.004) was associated with decreased PTB risk. Except for the MCSF-BW association, all above associations surpassed the Bonferroni corrected threshold. The MVMR results revealed that MIF, SDF1a, MIP1b, MCSF and IP10 composed cytokine networks, associated with offspring's BW. Risk factors analysis indicated that the above causal associations might be mediated by smoking behaviors. Conclusion: These findings suggest the causal associations of several cytokines with adverse pregnancy outcomes, which were potentially mediated by smoking and obesity. Some of the results did not been corrected through multiple tests and larger samples verification is required in further studies.

Reporting and risk of bias of prediction models based on machine learning methods in preterm birth: A systematic review

INTRODUCTION

There was limited evidence on the quality of reporting and methodological quality of prediction models using machine learning methods in preterm birth. This systematic review aimed to assess the reporting quality and risk of bias of a machine learning-based prediction model in preterm birth.

MATERIAL AND METHODS

We conducted a systematic review, searching the PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine disk, VIP Database, and WanFang Data from inception to September 27, 2021. Studies that developed (validated) a prediction model using machine learning methods in preterm birth were included. We used the Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) statement and Prediction model Risk of Bias Assessment Tool (PROBAST) to evaluate the reporting quality and the risk of bias of included studies, respectively. Findings were summarized using descriptive statistics and visual plots. The protocol was registered in PROSPERO (no. CRD 42022301623).

RESULTS

Twenty-nine studies met the inclusion criteria, with 24 development-only studies and 5 development-with-validation studies. Overall, TRIPOD adherence per study ranged from 17% to 79%, with a median adherence of 49%. The reporting of title, abstract, blinding of predictors, sample size justification, explanation of model, and model performance were mostly poor, with TRIPOD adherence ranging from 4% to 17%. For all included studies, 79% had a high overall risk of bias, and 21% had an unclear overall risk of bias. The analysis domain was most commonly rated as high risk of bias in included studies, mainly as a result of small effective sample size, selection of predictors based on univariable analysis, and lack of calibration evaluation.

CONCLUSIONS

Reporting and methodological quality of machine learning-based prediction models in preterm birth were poor. It is urgent to improve the design, conduct, and reporting of such studies to boost the application of machine learning-based prediction models in preterm birth in clinical practice.

Spontaneous preterm birth: Involvement of multiple feto-maternal tissues and organ systems, differing mechanisms, and pathways

Survivors of preterm birth struggle with multitudes of disabilities due to improper in utero programming of various tissues and organ systems contributing to adult-onset diseases at a very early stage of their lives. Therefore, the persistent rates of low birth weight (birth weight < 2,500 grams), as well as rates of neonatal and maternal morbidities and mortalities, need to be addressed. Active research throughout the years has provided us with multiple theories regarding the risk factors, initiators, biomarkers, and clinical manifestations of spontaneous preterm birth. Fetal organs, like the placenta and fetal membranes, and maternal tissues and organs, like the decidua, myometrium, and cervix, have all been shown to uniquely respond to specific exogenous or endogenous risk factors. These uniquely contribute to dynamic changes at the molecular and cellular levels to effect preterm labor pathways leading to delivery. Multiple intervention targets in these different tissues and organs have been successfully tested in preclinical trials to reduce the individual impacts on promoting preterm birth. However, these preclinical trial data have not been effectively translated into developing biomarkers of high-risk individuals for an early diagnosis of the disease. This becomes more evident when examining the current global rate of preterm birth, which remains staggeringly high despite years of research. We postulate that studying each tissue and organ in silos, as how the majority of research has been conducted in the past years, is unlikely to address the network interaction between various systems leading to a synchronized activity during either term or preterm labor and delivery. To address current limitations, this review proposes an integrated approach to studying various tissues and organs involved in the maintenance of normal pregnancy, promotion of normal parturition, and more importantly, contributions towards preterm birth. We also stress the need for biological models that allows for concomitant observation and analysis of interactions, rather than focusing on these tissues and organ in silos.