Care for women with prior preterm birth

The influence of previous preterm birth with singleton pregnancy on the risk of recurrence in subsequent twin pregnancy: a meta-analysis

BACKGROUND

Preterm birth is a significant obstetrical concern around the globe. With this study, we aimed to determine whether a prior singleton pregnancy preterm birth increases the likelihood of preterm birth in subsequent twin pregnancies. We designed his systematic review to provide valuable information for pregnant women and obstetricians during counselling and for individuals involved in the planning of preventive strategies.

METHODS

We comprehensively searched the PubMed, Embase and Scopus databases to identify relevant studies published until October 2023 following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We applied a random-effects meta-analysis to the data gathered from the selected studies.

RESULTS

Among the 460 initially identified studies, only eight met the eligibility criteria. The analysis of incidence revealed an event rate of 9.5% (95% CI, 4.4-19.5%) for a history of preterm singleton birth in the cohort of women with subsequent twin pregnancies. Subgroup analyses focused on the risk of preterm twin births (<37 weeks, <34 weeks and <32 weeks) in women with prior preterm singleton births. Our results revealed a significantly elevated risk of subsequent preterm twin births associated with prior preterm singleton births at <37 weeks (OR, 2.94; 95% CI, 1.99-4.33; p < .001), <34 weeks (OR, 1.89; 95% CI, 1.67-2.14; p < .001) and <32 weeks (OR, 2.51; 95% CI, 1.58-3.99; p < .001), without heterogeneity in the included studies.

CONCLUSIONS

Our systematic analysis indicates a consistent and statistically significant association between a history of preterm singleton births and preterm twin births at various gestational ages. These findings underscore the importance of the obstetric history during assessments to predict the risk of preterm births in twin pregnancies. Clinicians should monitor pregnancies with a history of preterm singleton births, as targeted interventions and improved prenatal care can mitigate the risk of preterm birth during twin pregnancies.

The effect of chorionicity on maternal and neonatal outcomes in triplet pregnancies

OBJECTIVE

Triplet gestations are associated with increased maternal, fetal, and neonatal complications particularly early and extreme preterm delivery. Identifying and interrupting the preterm delivery cascade could prevent the fetal, neonatal, and long-term childhood complications. The shared circulation and placental vascular anastomosis are responsible for the occurrence of twin-to-twin transfusion syndrome, selective fetal growth restriction as well as the higher risk of morbidity and mortality observed in mono and dichorionic compared to trichorionic triplet gestations. Thus, the aim of this study was to determine the effect of chorionicity on maternal, fetal, and neonatal outcomes of triplet pregnancies as it has not been fully ascertained.

STUDY DESIGN

A retrospective population-based cohort study of 125 parturient with triplets' pregnancy who delivered at a single tertiary hospital.

RESULTS

98 trichorionic and 27 dichorionic gestations were included. Maternal demographic and obstetric characteristics as well as pregnancy and postpartum complications were similar in the two study groups. The median gestational age at delivery was lower among dichorionic than trichorionic triplet gestations (median 31 vs 33 weeks, p < 0.046). Early (<32 weeks) and extreme preterm delivery (<28 weeks) were more prevalent in the dichorionic than the trichorionic group (early - 56 % vs 34 %, p < 0.038; extreme - 33.3 % vs 8 %, p < 0.002). We found no difference in fetal or newborns' complications and characteristics between the groups. However, the rate of neonatal death was significantly higher in the dichorionic compared to trichorionic triplet gestations (22 % vs 7 %, p < 0.038). A multivariate logistic regression model to determine the variables that contribute to early preterm delivery in triplet gestations showed that women who experienced a past preterm delivery had an independently higher risk for early preterm delivery in the triplet gestation (adj. OR 5.91, 95 % CI 1.16-30.03). Neither maternal age nor chorionicity were found to be independent risk factors for early preterm delivery.

CONCLUSIONS

Dichorionic triplet gestations exhibit a higher rate of early (<32 weeks) and extreme (<28 weeks) preterm delivery and are more prone to neonatal death compared to trichorionic gestations. Past preterm delivery is an independent risk factor for early preterm delivery in a triplet gestation.

Speculum-free portable preterm imaging system

Significance

Preterm birth is defined as a birth before 37 weeks of gestation and is one of the leading contributors to infant mortality rates globally. Premature birth can lead to life-long developmental impairment for the child. Unfortunately, there is a significant lack of tools to diagnose preterm birth risk, which limits patient care and the development of new therapies.

Aim

To develop a speculum-free, portable preterm imaging system (PPRIM) for cervical imaging; testing of the PPRIM system to resolve polarization properties of birefringent samples; and testing of the PPRIM under an IRB on healthy, non-pregnant volunteers for visualization and polarization analysis of cervical images.

Approach

The PPRIM can perform 4 × 3 Mueller-matrix imaging to characterize the remodeling of the uterine cervix during pregnancy. The PPRIM is built with a polarized imaging probe and a flexible insertable sheath made with a compatible flexible rubber-like material to maximize comfort and ease of use.

Results

The PPRIM device is developed to meet specific design specifications as a speculum-free, portable, and comfortable imaging system with polarized imaging capabilities. This system comprises a main imaging component and a flexible silicone inserter. The inserter is designed to maximize comfort and usability for the patient. The PPRIM shows high-resolution imaging capabilities at the 20 mm working distance and 25 mm circular field of view. The PPRIM demonstrates the ability to resolve birefringent sample orientation and full field capture of a healthy, non-pregnant cervix.

Conclusion

The development of the PPRIM aims to improve access to the standard of care for women's reproductive health using polarized Mueller-matrix imaging of the cervix and reduce infant and maternal mortality rates and better quality of life.

The role of neighborhood deprivation in the cervicovaginal microbiota

BACKGROUND

Lactobacillus-deficient cervicovaginal microbiota is associated with spontaneous preterm birth and is more common among Black individuals. Persistent racial segregation in the United States has led to differential neighborhood exposures by race that can affect pregnancy outcomes. The extent to which neighborhood exposures may explain racial differences in the cervicovaginal microbiota is unknown.

OBJECTIVE

This study aimed to determine whether neighborhood deprivation, defined as material community deprivation, is associated with a Lactobacillus-deficient cervicovaginal microbiota in a prospective cohort of pregnant individuals. Our hypothesis was that racial differences in neighborhood deprivation may explain the higher prevalence of Lactobacillus-deficient cervicovaginal microbiota in Black birthing people.

STUDY DESIGN

This study analyzed data from Motherhood and Microbiome, a prospective pregnancy cohort enrolled from prenatal clinics in a single hospital system 2013-2016 in which a Lactobacillus-deficient cervicovaginal microbiota was previously shown to be associated with spontaneous preterm birth. This study geocoded addresses to obtain census tract neighborhood deprivation data from the Brokamp Nationwide Community Deprivation Index that uses weighted proportions of poverty, income, public assistance, lack of health insurance, and vacant housing. Generalized linear mixed models quantified associations of deprivation with the cervicovaginal microbiota accounting for geographic clustering by census tract and potential confounders. Because of different distributions of neighborhood deprivation and the cervicovaginal microbiota, race-stratified models were used. Mediation analyses quantified the extent to which deprivation may contribute to racial differences in the cervicovaginal microbiota.

RESULTS

Higher neighborhood deprivation was associated with a Lactobacillus-deficient cervicovaginal microbiota. Per standard deviation increment of deprivation, participants had 28% higher adjusted odds (adjusted odds ratio, 1.28; 95% confidence interval, 1.04-1.58) of a Lactobacillus-deficient microbiota. Black participants had higher odds of a Lactobacillus-deficient microbiota than White participants (adjusted odds ratio, 4.00; 95% confidence interval, 2.05-8.26), and mediation analysis revealed that deprivation accounted for 22% (P=.046) of that disparity.

CONCLUSION

Neighborhood deprivation was associated with Lactobacillus-deficient cervicovaginal microbiota and may partially explain Black-White disparities in the cervicovaginal microbiota. Mechanistic studies to explore how environmental exposures modify the cervicovaginal microbiota are warranted to identify novel opportunities for future interventional strategies to prevent preterm birth. As the findings demonstrate a potential biological effect from neighborhood conditions, policies that drive urban planning should be explored to improve pregnancy outcomes.

Does perinatal management have the potential to reduce the risk of intraventricular hemorrhage in preterm infants?

Background

Intraventricular hemorrhage (IVH) is an important cause of neurodevelopmental impairment in preterm infants. A number of risk factors for IVH have already been proposed; however, some controversies regarding optimal perinatal management persist. This study aimed to identify perinatal and neonatal attributes associated with IVH in a representative population of preterm infants.

Methods

Perinatal data on 1,279 very preterm infants (<32 weeks of gestation) admitted to a tertiary neonatal intensive care unit were analyzed. The records were assessed using univariate analysis and logistic regression model to evaluate the risk factors for any and high-grade IVH (grade III-IV according to the classification by Papile) within the first week after birth.

Results

The incidence of any IVH was 14.3% (183/1,279); the rate of low-grade (I-II) and high-grade (III-IV) IVH was 9.0% (115/1,279) and 5.3% (68/1,279), respectively. Univariate analysis revealed multiple factors significantly associated with intraventricular hemorrhage: lower gestational age and birth weight, absence of antenatal steroids, vaginal delivery, low Apgar score at 5 min, delivery room intubation, surfactant administration, high frequency oscillation, pulmonary hypertension, pulmonary hemorrhage, tension pneumothorax, persistent ductus arteriosus, hypotension and early onset sepsis. Logistic regression confirmed lower gestational age, vaginal delivery, ductus arteriosus and early onset sepsis to be independent predictors for any IVH. Pulmonary hemorrhage, tension pneumothorax and early onset sepsis were independent risk factors for high-grade IVH. Complete course of antenatal steroids was associated with a lower risk for any (odds ratio 0.58, 95% confidence interval 0.39-0.85; P = .006) and for high-grade intraventricular hemorrhage (odds ratio 0.36, 95% confidence interval 0.20-0.65; P < .001).

Conclusion

The use of antenatal steroids and mode of delivery are crucial in the prevention of IVH; however, our study did not confirm the protective effect of placental transfusion. Severe respiratory insufficiency and circulatory instability remain to be powerful contributors to the development of IVH. Early detection and management of perinatal infection may also help to reduce the rate of brain injury and improve neurodevelopment in high-risk newborns.

Review paper: The importance of consideration of collagen cross-links in computational models of collagen-based tissues

Collagen as the main protein in Extra Cellular Matrix (ECM) is the main load-bearing component of fibrous tissues. Nanostructure and architecture of collagen fibrils play an important role in mechanical behavior of these tissues. Extensive experimental and theoretical studies have so far been performed to capture these properties, but none of the current models realistically represent the complexity of network mechanics because still less is known about the collagen's inner structure and its effect on the mechanical properties of tissues. The goal of this review article is to emphasize the significance of cross-links in computational modeling of different collagen-based tissues, and to reveal the need for continuum models to consider cross-links properties to better reflect the mechanical behavior observed in experiments. In addition, this study outlines the limitations of current investigations and provides potential suggestions for the future work.

Predicting preterm birth using machine learning techniques in oral microbiome

Preterm birth prediction is essential for improving neonatal outcomes. While many machine learning techniques have been applied to predict preterm birth using health records, inflammatory markers, and vaginal microbiome data, the role of prenatal oral microbiome remains unclear. This study aimed to compare oral microbiome compositions between a preterm and a full-term birth group, identify oral microbiome associated with preterm birth, and develop a preterm birth prediction model using machine learning of oral microbiome compositions. Participants included singleton pregnant women admitted to Jeonbuk National University Hospital between 2019 and 2021. Subjects were divided into a preterm and a full-term birth group based on pregnancy outcomes. Oral microbiome samples were collected using mouthwash within 24 h before delivery and 16S ribosomal RNA sequencing was performed to analyze taxonomy. Differentially abundant taxa were identified using DESeq2. A random forest classifier was applied to predict preterm birth based on the oral microbiome. A total of 59 women participated in this study, with 30 in the preterm birth group and 29 in the full-term birth group. There was no significant difference in maternal clinical characteristics between the preterm and the full-birth group. Twenty-five differentially abundant taxa were identified, including 22 full-term birth-enriched taxa and 3 preterm birth-enriched taxa. The random forest classifier achieved high balanced accuracies (0.765 ± 0.071) using the 9 most important taxa. Our study identified 25 differentially abundant taxa that could differentiate preterm and full-term birth groups. A preterm birth prediction model was developed using machine learning of oral microbiome compositions in mouthwash samples. Findings of this study suggest the potential of using oral microbiome for predicting preterm birth. Further multi-center and larger studies are required to validate our results before clinical applications.

Assessment of cervical softening and the prediction of preterm birth (STIPP): protocol for a prospective cohort study

INTRODUCTION

Preterm birth (PTB) is among the leading causes of perinatal and childhood morbidity and mortality. Therefore, accurate identification of pregnant women at high risk of PTB is key to enable obstetric healthcare professionals to apply interventions that improve perinatal and childhood outcomes. Serial transvaginal cervical length measurement is used to screen asymptomatic pregnant women with a history of PTB and identify those at high risk for a recurrent PTB. Cervical length measurement, fetal fibronectin test or a combination of both can be used to identify women at high risk of PTB presenting with symptoms of threatened PTB. The predictive capacity of these methods can be improved. Cervical softening is a precursor of cervical shortening, effacement and dilatation and could be a new marker to identify women a high risk of PTB. However, the predictive value of cervical softening to predict spontaneous PTB still needs to be determined.

METHODS AND ANALYSIS

This is a single-centre, prospective cohort study, conducted at the Amsterdam University Medical Centers in the Netherlands. Cervical softening will be investigated with a non-invasive CE-marked device called the Pregnolia System. This device has been developed to evaluate consistency of the cervix based on tissue elasticity. Two different cohorts will be investigated. The first cohort includes women with a history of spontaneous PTB <34 weeks. These women undergo biweekly measurements between 14 and 24 weeks of gestation. The second cohort includes women with symptoms of threatened PTB. These women will receive the measurement once at presentation between 24 and 34 weeks of gestation. The primary outcome is spontaneous PTB before 34 weeks for women with a history of PTB and delivery within 7 days for women with threatened PTB. The minimum sample size required to analyse the primary outcome is 227 women in the cohort of women with a history of PTB and 163 women in the cohort of women with symptoms of threatened PTB. Once this number is achieved, the study will be continued to investigate secondary objectives.

ETHICS AND DISSEMINATION

The study is approved by the Medical Ethics Committee of Amsterdam UMC (METC2022.0226). All patients will give oral and written informed consent prior to study entry. Results will be disseminated via a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT05477381.

A Comparison of Vaginal and Intramuscular Progesterone for the Prevention of Recurrent Preterm Birth

OBJECTIVE

This study aimed to examine whether vaginal progesterone is noninferior to 17-α hydroxyprogesterone caproate (17OHP-C) in the prevention of recurrent preterm birth (PTB).

STUDY DESIGN

This retrospective cohort study included singleton pregnancies among women with a history of spontaneous PTB who received prenatal care at a single tertiary center from 2011 to 2016. Pregnancies were excluded if progesterone was not initiated prior to 24 weeks or the fetus had a major congenital anomaly. The primary outcome was PTB <37 weeks. A priori, noninferiority was to be established if the upper bound of the adjusted two-sided 90% confidence interval (CI) for the difference in PTB fell below 9%. Inverse probability of treatment weighting (IPTW) was used to carefully control for confounding associated with choice of treatment and PTB. Adjusted differences in PTB proportions were estimated via IPTW regression, with standard errors adjustment for multiple pregnancies per woman. Secondary outcomes included PTB <34 and <28 weeks, spontaneous PTB, neonatal intensive care unit admission, and gestational age at delivery.

RESULTS

Among 858 pregnancies, 41% (n = 353) received vaginal progesterone and 59% (n = 505) were given 17OHP-C. Vaginal progesterone use was more common later in the study period, and among women who established prenatal care later, had prior PTBs at later gestational ages, and whose race/ethnicity was neither non-Hispanic white nor non-Hispanic Black. Vaginal progesterone did not meet noninferiority criteria compared with 17-OHPC in examining PTB <37 weeks, with an IPTW adjusted difference of 3.4% (90% CI: -3.5, 10.3). For secondary outcomes, IPTW adjusted differences between treatment groups were generally small and CIs were wide.

CONCLUSION

We could not conclude noninferiority of vaginal progesterone to 17OHP-C; however, women and providers may be willing to accept a larger difference (>9%) when considering the cost and availability of vaginal progesterone versus 17OHP-C. A well-designed randomized trial is needed.

KEY POINTS

· Vaginal progesterone is not noninferior to 17OHP-C.. · PTB risk may be 10% higher with vaginal progesterone.. · Associations did not differ based on obesity status..

What now? A critical evaluation of over 20 years of clinical and research experience with 17-alpha hydroxyprogesterone caproate for recurrent preterm birth prevention

Spontaneous preterm birth is multifactorial, and underlying etiologies remain incompletely understood. Supplementation with progestogens, including 17-alpha hydroxyprogesterone caproate has been a mainstay of prematurity prevention strategies in the United States in the last 2 decades. Following a recent negative confirmatory trial, 17-alpha hydroxyprogesterone caproate was withdrawn from the US market and is currently available only through clinical research studies. This expert review summarized clinical and research data regarding the use of 17-alpha hydroxyprogesterone caproate in the United States from 2003 to 2023 for recurrent prematurity prevention. In 17-alpha hydroxyprogesterone caproate. The history of the use, mechanisms of action, clinical trial results, and efficacy by clinical and biologic criteria of 17-alpha hydroxyprogesterone caproate are presented. We report that disparate findings and conclusions between similarly designed rigorous studies may reflect differences in a priori risk and population incidence and extreme care should be taken in interpreting the studies and making decisions regarding efficacy of 17-alpha hydroxyprogesterone caproate for the prevention of preterm birth. The likelihood of improved obstetrical outcomes after receiving 17-alpha hydroxyprogesterone caproate may vary by clinical factors (eg, body mass index), plasma drug concentrations, and genetic factors, although the identification of individuals most likely to benefit remains imperfect. It is crucial for the medical community to recognize the importance of preserving the decades-long efforts invested in preventing recurrent preterm birth in the United States. Moreover, it is important that we thoroughly and thoughtfully evaluate 17-alpha hydroxyprogesterone caproate as a promising contender for future well-executed prematurity studies.

The amniotic fluid proteome predicts imminent preterm delivery in asymptomatic women with a short cervix

Preterm birth, the leading cause of perinatal morbidity and mortality, is associated with increased risk of short- and long-term adverse outcomes. For women identified as at risk for preterm birth attributable to a sonographic short cervix, the determination of imminent delivery is crucial for patient management. The current study aimed to identify amniotic fluid (AF) proteins that could predict imminent delivery in asymptomatic patients with a short cervix. This retrospective cohort study included women enrolled between May 2002 and September 2015 who were diagnosed with a sonographic short cervix (< 25 mm) at 16–32 weeks of gestation. Amniocenteses were performed to exclude intra-amniotic infection; none of the women included had clinical signs of infection or labor at the time of amniocentesis. An aptamer-based multiplex platform was used to profile 1310 AF proteins, and the differential protein abundance between women who delivered within two weeks from amniocentesis, and those who did not, was determined. The analysis included adjustment for quantitative cervical length and control of the false-positive rate at 10%. The area under the receiver operating characteristic curve was calculated to determine whether protein abundance in combination with cervical length improved the prediction of imminent preterm delivery as compared to cervical length alone. Of the 1,310 proteins profiled in AF, 17 were differentially abundant in women destined to deliver within two weeks of amniocentesis independently of the cervical length (adjusted p-value < 0.10). The decreased abundance of SNAP25 and the increased abundance of GPI, PTPN11, OLR1, ENO1, GAPDH, CHI3L1, RETN, CSF3, LCN2, CXCL1, CXCL8, PGLYRP1, LDHB, IL6, MMP8, and PRTN3 were associated with an increased risk of imminent delivery (odds ratio > 1.5 for each). The sensitivity at a 10% false-positive rate for the prediction of imminent delivery by a quantitative cervical length alone was 38%, yet it increased to 79% when combined with the abundance of four AF proteins (CXCL8, SNAP25, PTPN11, and MMP8). Neutrophil-mediated immunity, neutrophil activation, granulocyte activation, myeloid leukocyte activation, and myeloid leukocyte-mediated immunity were biological processes impacted by protein dysregulation in women destined to deliver within two weeks of diagnosis. The combination of AF protein abundance and quantitative cervical length improves prediction of the timing of delivery compared to cervical length alone, among women with a sonographic short cervix.

Obstetric History and Risk of Short Cervix in Women with a Prior Preterm Birth

OBJECTIVE

We aimed to assess the relationship between obstetric history and incidence of short cervical length (CL) at <24 weeks gestational age (GA) in women with a prior spontaneous preterm birth (PTB).

STUDY DESIGN

Women with a singleton gestation and a history of spontaneous PTB on progesterone who received prenatal care at a single center from 2011 to 2016 were included. Those who did not undergo screening or had a history-indicated cerclage were excluded. The associations between short CL (<25 mm) before 24 weeks and obstetrical factors including: number of prior PTBs, history of term birth, and GA of earliest spontaneous PTB were estimated through modified Poisson regression, adjusting for confounding factors. Multiple pregnancies for the same woman were accounted for through robust sandwich standard error estimation.

RESULTS

Among 773 pregnancies, 29% (n = 224) had a CL <25 mm before 24 weeks. The number of prior PTBs was not associated with short CL, but a prior full-term delivery conferred a lower risk of short CL (absolute risk reduction or aRR 0.79, 95% CI 0.63-1.00). Earliest GA of prior spontaneous PTB was associated with short CL. The strongest association was observed in women with a prior PTB at 16^0/7 to 23^6/7weeks (aRR 1.98, 95% CI: 1.46-2.70), compared with those with deliveries at 34^0/7 to 36^6/7 weeks. Yet, even women whose earliest PTB was 34^0/7 to 36^6/7 weeks remained at risk for a short CL, as 21% had a CL <25 mm. The number of prior PTBs did not modify the effect of GA of the earliest prior PTB (interaction test: p = 0.70).

CONCLUSION

GA of earliest spontaneous PTB, but not the number of prior PTBs, is associated with short CL. Nevertheless, women with a history of later PTBs remain at sufficiently high risk of having a short CL at <24 weeks gestation that we cannot recommend modifications to existing CL screening guidelines in this group of women.

KEY POINTS

· Prior 16 to 236/7 weeks birth is a key risk factor for CL <25 mm.. · One in five women with prior late PTB had a short CL.. · Number of PTBs is a less important risk factor..

Progesterone, cervical cerclage or cervical pessary to prevent preterm birth: a decision-making analysis of international guidelines

Objective

The aim of this study was to investigate guidelines on preterm birth, analyze decision-criteria, and to identify consensus and discrepancies among these guidelines.

Design

Objective consensus analysis of guidelines.

Sample

Ten international guidelines on preterm birth.

Methods

Relevant decision criteria were singleton vs. twin pregnancy, history, cervical length, and cervical surgery / trauma or Mullerian anomaly. Eight treatment recommendations were extracted. For each decision-making criteria the most commonly recommended treatment was identified, and the level of consensus was evaluated.

Main outcome measures

Consensus and Discrepancies among recommendations.

Results

In a case of singleton pregnancies with no history of preterm birth and shortened cervix, most guidelines recommend progesterone. In singleton pregnancies with a positive history and shortened cervix, all guidelines recommend a cerclage as an option, alternative or conjunct to progesterone. The majority of the guidelines advise against treatment in twin pregnancies.

Conclusions

A shortened cervix and a history of preterm birth are relevant in singleton pregnancies. In twins, most guidelines recommend no active treatment.

Tweetable abstract

Among international guidelines a shortened cervix and a history of preterm birth are relevant in singleton pregnancies. With no history of preterm birth and with a shortened cervix most guidelines recommend progesterone treatment.

Guidelines on prevention of preterm birth

This guideline has been prepared by the National Maternal Fetal Medicine guidelines committee and approved by the Society of Obstetricians and Gynecologists Pakistan. These recommendations will enable the practicing clinicians to optimally manage pregnancies at risk of preterm birth.

Interconception Preventive Care and Recurrence of Pregnancy Complications for Medicaid-Insured Women

Background: Pregnancy complications may recur and are associated with potentially modifiable risks. The role of interconception preventive care in reducing repeat pregnancy complications is understudied. Materials and Methods: This retrospective cohort used 2007-2012 Medicaid claims from 12 states. Included women who had an index birth complicated by prematurity, hypertension, or diabetes, a subsequent birth within 36 months, and Medicaid eligibility for ≥11 of 12 months after index birth. Logistic regression assessed for an association between the exposure of preventive visits in the year after index birth and primary outcomes of prematurity, hypertension, or diabetes in the subsequent pregnancy. Regression adjusted for confounders including demographics (age, race and ethnicity, rural residence, state), index pregnancy features (complications, prenatal visits, multiple gestation, maternal and infant length of stay, year), visits to address complications in the index birth, and interpregnancy interval. Results: Of 17,372 women, mean age was 24.3 ± 5.3 years, and race/ethnicity was 50.3% non-Hispanic White, 27.2% non-Hispanic Black, and 11.9% Hispanic. In the index pregnancy 43.3% experienced prematurity, 39.2% experienced hypertension, and 34.2% experienced diabetes. In the year after the index pregnancy, 54.7% had at least one preventive visit. In the second pregnancy, 47.7% experienced prematurity, hypertension, or diabetes. Recurrence rates were 28.1% for preterm birth, 38.0% for hypertension, and 48.3% for diabetes. Preventive visits were associated with reduced hypertension in the subsequent pregnancy (OR 0.88, 95% CI 0.82-0.97) but not reduced preterm birth or diabetes. Conclusions: Preventive visits after an index birth complicated by prematurity, hypertension, or diabetes were associated with 10% lower odds of hypertension in a subsequent pregnancy, but not with reductions in diabetes or prematurity. Some complications may be more amenable to interconception preventive services than others.

The swelling behavior of the mouse cervix: Changing kinetics with osmolarity and the role of hyaluronan in pregnancy

The cervical remodeling process during pregnancy is characterized by progressive compositional and structural changes in the tissues extra-cellular matrix (ECM). Appropriately timed remodeling is critical for healthy gestation and prevention of premature cervical softening leading to preterm birth (PTB). Modification of the ECM glycosaminoglycans (GAGs) content with advancing pregnancy, especially the non-sulfated GAG hyaluronan (HA), is a fundamental change associated with cervical remodeling. While GAGs have numerous physiological roles, the mechanical consequence of evolving GAG content on cervical structure-function behavior remains an open question. Additionally, an understanding of cervical swelling properties, postulated to be regulated in part by GAGs, is required for the appropriate definition of a reference configuration for mechanical tests and to enhance biological understanding. To investigate cervical swelling, osmotic loading tests are conducted on isolated wild type mouse cervices throughout pregnancy. These tests are performed in various osmolarity solutions to assess the influence of the media on swelling kinetics. A genetically altered strain of mice with depletion of cervical HA is also tested to elucidate the contribution of HA to tissue swelling. Results show ex vivo cervical swelling is significant with volume changes ranging from 20 to 100% after 3h of free swelling. The swelling kinetics depend highly on osmolarity of the media and is altered with advancing pregnancy. The contribution of HA to swelling is only significant in hypo-osmotic solution when HA cervical content is high at the end of pregnancy. In summary, it is critical to account for swelling deformation mechanisms after excision in mechanical experiments. STATEMENT OF SIGNIFICANCE: The cervical extracellular matrix (ECM) undergoes drastic changes to fulfill the functional change of the cervix during pregnancy. Inappropriate timing for this transformation can result in preterm birth, a severe clinical challenge. One of the fundamental changes of the cervical ECM is the significant modification of the glycosaminoglycan content, especially hyaluronan (HA), which is thought to contribute significantly to the swelling and mechanical properties of the cervix. This study aims to measure the swelling kinetics of cervical tissue during pregnancy and to investigate the role of HA in these swelling tendencies. Results show the significant swelling of cervical tissue, which evolves as pregnancy progresses, highlighting a key material property feature of the remodeled cervix. Using a mouse strain with a cervical HA depletion, this work shows HA contributes to the swelling trends of late-term cervical tissue, in a hypo-osmotic solution.

Healthy preconception and early-pregnancy lifestyle and risk of preterm birth: a prospective cohort study

BACKGROUND

Preterm birth (PTB) remains a leading cause of neonatal mortality and long-term morbidity. Individual factors have been linked to PTB risk. The impact of a healthy lifestyle, with multiple modifiable prenatal factors, remains unknown.

OBJECTIVES

We aimed to examine the associations of preconceptional and early-pregnancy low-risk modifiable factors (individually and in combination) with PTB risk.

METHODS

This prospective cohort study included 2449 women with singleton pregnancies in the Pregnancy Environment and Lifestyle Study. PTB was defined as ultrasound-confirmed obstetric estimate-based gestational age at delivery <37 wk. A set of low-risk modifiable factors were identified: healthy weight (prepregnancy BMI: 18.5-24.9 kg/m2) based on clinical measurements and high-quality diet (Alternate Healthy Eating Index-Pregnancy score ≥75th percentile) and low-to-moderate stress during early pregnancy (Perceived Stress Scale score <75th percentile) assessed at gestational weeks 10-13. Poisson regression estimated adjusted relative risk (aRR) of PTB in association with individual and combined low-risk modifiable prenatal factors, adjusting for sociodemographic, clinical, and other prenatal factors.

RESULTS

One hundred and sixty women (6.5%) delivered preterm. Risk of PTB was lower among women who had a healthy weight (aRR: 0.58; 95% CI: 0.39, 0.86), high-quality diet (aRR: 0.68; 95% CI: 0.39, 0.99), and low-to-moderate stress (aRR: 0.60; 95% CI: 0.41, 0.88). Women with 1, 2, or 3 low-risk modifiable prenatal factors compared with none had a 38% (aRR: 0.72; 95% CI: 0.45, 1.16), 51% (aRR: 0.49; 95% CI: 0.29, 0.84), or 70% (aRR: 0.30; 95% CI: 0.13, 0.70) lower PTB risk, respectively. Associations of having ≥1 low-risk factor with PTB risk were more pronounced for medically indicated than for spontaneous PTB and for late than for early or moderate PTB. Associations also varied by race or ethnicity, although with overlapping 95% CIs.

CONCLUSIONS

A healthy prenatal lifestyle with multiple low-risk modifiable factors was associated with lower risk of PTB. Our findings may inform multicomponent preconceptional or early-pregnancy prevention strategies to mitigate PTB risk.

Cervical length distribution and other sonographic ancillary findings of singleton nulliparous patients at midgestation

BACKGROUND

Short cervix at midgestation, the presence of intraamniotic debris, and cervical funneling are risk factors for preterm birth; however, cervical length measurements and cutoffs are not well documented among pregnant patients of different gestational ages and self-reported races and ethnicities.

OBJECTIVE

This study aimed to describe the distribution of cervical length and frequency of funneling and debris at midgestation in nulliparous women by gestational age and race/ethnicity.

STUDY DESIGN

This secondary analysis of screening data from a multicenter treatment trial of singleton nulliparous patients with short cervix was conducted at 14 geographically distributed, university-affiliated medical centers in the United States. Singleton nulliparous patients with no known risk factors for preterm birth were screened for trial participation and asked to undergo a transvaginal ultrasound to measure cervical length by a certified sonographer. The distribution of cervical length and the frequency of funneling and debris were assessed for each gestational age week (16-22 weeks) and stratified by self-reported race and ethnicity, which for this study were categorized as White, Black, Hispanic, and other. Patients enrolled in the randomized trial were excluded from this analysis.

RESULTS

A total of 12,407 nulliparous patients were included in this analysis. The racial or ethnic distribution of the study participants was as follows: White, 41.6%; Black, 29.6%; Hispanic, 24.2%; and others, 4.6%. The 10th percentile cervical length for the entire cohort was 31.1 mm and, when stratified by race and ethnicity, 31.9 mm for White, 30.2 mm for Black, 31.4 mm for Hispanic, and 31.2 mm for patients of other race and ethnicity (P<.001). At each gestational age, the cervical length corresponding to the tenth percentile was shorter in Black patients. The 25 mm value commonly used to define a short cervix and thought to represent the 10th percentile ranged from 1.3% to 5.4% across gestational age weeks and 1.0% to 3.8% across race and ethnicity groups. Black patients had the highest rate of funneling (2.6%), whereas Hispanic and Black patients had higher rates of intraamniotic debris than White and other patients (P<.001).

CONCLUSION

Black patients had shorter cervical length and higher rates of debris and funneling than White patients. The racial and ethnic disparities in sonographic midtrimester cervical findings may provide insight into the racial disparity in preterm birth rates in the United States.

PretermConnect: Leveraging mobile technology to mitigate social disadvantage in the NICU and beyond

Preterm birth (PTB) - delivery prior to 37-weeks gestation - disproportionately affects low-income and minority populations and leads to substantial infant morbidity and mortality. The time following a PTB represents an optimal window for targeted interventions that encourage mothers to prioritize their own health and that of their babies. Healthcare teams can leverage digital strategies to address maternal and infant needs in this postpartum period, both in the neonatal intensive care unit and beyond. We therefore developed PretermConnect, a mobile app designed to educate, engage, and empower women at risk for PTB. This article describes the participant-centered design approach of PretermConnect, with preliminary findings from focus groups and co-design sessions in different community settings and suggested future directions for mobile technologies in population health. Apps such as PretermConnect can mitigate social disadvantage by serving as remote monitoring tools, providing social support, preventing recurrent PTB and lowering infant mortality rates.

Sex differences in dopamine innervation and microglia are altered by synthetic progestin in neonatal medial prefrontal cortex

The synthetic progestin 17-α-hydroxyprogesterone caproate (17-OHPC) is commonly prescribed to pregnant women with a history of preterm delivery, despite little evidence of efficacy. The timing of 17-OHPC administration coincides with fetal mesocortical dopamine pathway development, yet the potential effects on cortical development and cognition are almost unknown. In rodent models, exposure to 17-OHPC significantly increased dopaminergic innervation of the medial prefrontal cortex (mPFC), an aberrant pattern of connectivity that may underlie deficits in cognitive flexibility observed in adulthood. In the present study, tyrosine hydroxylase (TH) immunoreactivity was used to determine whether 17-OHPC altered dopaminergic innervation of the mPFC during a neonatal period of synaptogenesis in males and females. Although there were no differences in the amount of TH-immunoreactive (-IR) fibres, there was a sex difference in TH-IR fibre distribution in deep layers of the prelimbic area (PL) mPFC; males had a narrower pattern of dopaminergic innervation than females. 17-OHPC exposure abolished these sex-specific patterns, such that 17-OHPC females had a narrower pattern in the PL than control females. In the infralimbic mPFC (IL), 17-OHPC males had a broader pattern of distribution of TH-immunoreactivity than control males with no differences in the amount of TH-IR fibres. 17-OHPC also created a sex difference in which males had a lower TH-IR fibre density than females. We also examined microglia, brain macrophages that play a key role in sculpting dopaminergic axon outgrowth in development, using phenotype as an indirect measure of microglial activity. Females had a greater number of reactive stout microglia compared to males in the PL, and males had more active round microglia than females in the IL. 17-OHPC treatment abolished the sex differences in both regions. These findings demonstrate that developmental exposure to 17-OHPC can exert differential effects in males and females and may diminish sex differences in cortical maturation.

Corticosteroids in Pregnancy for Preventing RDS: Overview of Systematic Reviews

The objective of this study was to analyze the available evidence of systematic reviews that evaluated the efficacy of antenatal corticosteroids in order to contribute to a reduction in magnitude and transcendence of respiratory distress syndrome of the newborn (RDS). Thus, an overview was conducted including all systematic reviews of randomized controlled trials (RCTs) that evaluated women who received corticosteroid treatment during pregnancy to prevent RDS. Therefore, a search strategy was developed using the terms "respiratory distress syndrome, newborn," "corticosteroids," "perinatal death," "neonatal death," "neonate," and "pregnancy." The electronic databases searched were MEDLINE, EMBASE, Cochrane Library, LILACS, and Google Scholar, for studies published until June 2020. We identified 354 references, 38 of which were relevant after the initial screening. Ten systematic reviews met the inclusion criteria. For RDS, 1522 cases occurred in the control group composed of 8716 participants, while in the intervention group was 1088 in 8740 participants (RR = 0.67, 95% CI 0.60-0.75). For neonatal death, 343 cases occurred in 5248 participants of the control group, while in the intervention group, there were 227 cases in 5246 participants (RR = 0.66, 95% CI 0.56-0.78). For perinatal death, there were 344 cases in 3345 participants in the control group, while in the intervention group, the number of cases was 264 in 3384 participants (RR = 0.72, 95% CI 0.58-0.89). Thus, the use of corticosteroids during pregnancy in women at risk of preterm birth is effective for the prevention of RDS in neonates and reducing the number of neonatal and perinatal deaths in preterm. PROSPERO protocol no: CRD42017074604.

Evaluation of the efficacy of vaginal progesterone in preventing preterm birth after abdominal trachelectomy

OBJECTIVE

To determine whether vaginal progesterone (VP) reduces the rate of preterm birth in pregnant women after abdominal trachelectomy (AT) for early-stage cervical cancer STUDY DESIGN: This is an interventional study with a historical cohort. For the interventional study participants who had singleton pregnancies after AT between October 2016 and September 2020, the administration of vaginal progesterone was started between 16⁺ and 19⁺⁶ weeks of gestation and discontinued at 34 weeks of gestation or at the time of delivery, rupture of membranes, or massive uterine bleeding. We investigated obstetric and neonatal outcomes among the study participants and compared them with outcomes of the historical control group participants, included women with singleton pregnancies after AT who were managed without VP at our institution between January 2007 and September 2016, using Fisher's exact test and the Mann-Whitney U test The main outcomes were the gestational age at delivery and incidence of preterm birth before 37 weeks and 34 weeks of gestation.

RESULT

Twelve pregnancies in ten women were included in the VP group. In contrast, 19 pregnancies in 17 women were included in the historical control group. The incidence of preterm birth at <37 weeks was 10/12 (83 %) in the VP group and 11/19 (58 %) in the control group. The incidence of preterm birth at <34 weeks was 6/12 (50 %) in the VP group and 9/19 (48 %) in the control group. The incidence of preterm birth in the two groups was similar, and the difference between the two groups was not statistically significant.

CONCLUSION

The administration of vaginal progesterone did not reduce the rate of preterm birth among pregnant women after AT.

The Importance of Clinical Presentation in Risk and Management of Recurrent Preterm Birth

OBJECTIVE

This study aimed to compare the risk of recurrent spontaneous preterm birth (sPTB), as well as cerclage efficacy, between groups stratified by phenotype of the index sPTB.

STUDY DESIGN

This is a retrospective cohort study of women with a history of sPTB. Included were women with a history of singleton sPTB who received progesterone in a subsequent pregnancy. Multifetal gestations and abdominal cerclage were excluded. Exposure groups were based upon the presenting symptom that preceded their first sPTB and included painless cervical dilation (PCD), preterm premature rupture of membranes (PPROM), and painful dilation (preterm labor [PTL]). Primary outcome was delivery <34 weeks in a subsequent pregnancy. Secondary outcomes included delivery <28 and <37 weeks. Rates were compared using the Chi-square test. Multivariable Poisson regression was used to adjust for confounders.

RESULTS

A total of 723 women were included. A total of 114 (16%) presented with PCD, 305 (42%) with PPROM, and 304 (42%) with PTL in their first sPTB. Cerclage in subsequent pregnancy was highest in the PCD group (42%) when compared with the PPROM (16%) and PTL (12%) groups. Rates of sPTB <34 and 37 weeks were similar among the groups. After adjusting for confounders, PCD was found to significantly increase the risk of recurrent sPTB <28 weeks (incidence rate ratio: 3.46 [1.09-11.0]; p = 0.04). Of the 121 women who underwent cerclage, there were no significant differences in rates of sPTB between the clinical presentation groups.

CONCLUSION

PCD as a specific phenotype of sPTB impacts recurrence of delivery before 28 weeks, but not at later gestational ages. In contrast, there was no significant association between clinical presentation of index sPTB and gestational latency in women who also underwent cerclage placement in a subsequent pregnancy. Our data suggest that clinical presentation is important with regards to recurrence of early sPTB, but not sPTB at later gestational ages.

KEY POINTS

· Phenotype is critical to understanding PTB.. · Phenotype is associated with recurrent PTB.. · Painless dilation is associated with recurrent PTB..

Risk factors for spontaneous preterm delivery

BACKGROUND

There is a substantial variation in rates of preterm delivery between different parts of the world. The understanding of these variations, as well as the biological mechanisms behind spontaneous preterm delivery, is limited. Although the benefit of antenatal interventions has been shown to be limited, using well-known risk factors for spontaneous preterm delivery to select the correct pregnant women for targeted interventions is important from both a medical and caregiving perspective.

OBJECTIVE

To provide an introduction to a substantial research area dealing with risk factors of spontaneous preterm delivery.

METHODS

Risk factors in this review were classified as demographical, obstetrical, and gynecological and those related to the current pregnancy according to high-quality evidence of recent literature.

RESULTS AND CONCLUSION

An introduction to a substantial research area in maternal and fetal medicine was provided that might help clinicians to better understand the risk factors related to preterm delivery and select the correct pregnant women for targeted interventions.

Vaginal compared with intramuscular progestogen for preventing preterm birth in high-risk pregnant women (VICTORIA study): a multicentre, open-label randomised trial and meta-analysis

OBJECTIVE

To compare the efficacy of two types of progestogen therapy for preventing preterm birth (PTB) and to review the relevant literature.

DESIGN

A multicentre, randomised, open-label, equivalence trial and a meta-analysis.

SETTING

Tertiary referral hospitals in South Korea.

POPULATION

Pregnant women with a history of spontaneous PTB or short cervical length (<25 mm).

METHODS

Eligible women were screened and randomised at 16-22 weeks of gestation to receive either 200 mg of vaginal micronised progesterone daily (vaginal group) or an intramuscular injection of 250 mg 17α-hydroxyprogesterone caproate weekly (IM group). Stratified randomisation was carried out according to participating centres and indications for progestogen therapy. This trial was registered at ClinicalTrials.gov (NCT02304237).

MAIN OUTCOME MEASURE

Preterm birth (PTB) before 37 weeks of gestation.

RESULTS

A total of 266 women were randomly assigned and a total of 247 women (119 and 128 women in the vaginal and IM groups, respectively) were available for the intention-to-treat analysis. Risks of PTB before 37 weeks of gestation did not significantly differ between the two groups (22.7 versus 25.8%, P = 0.571). The difference in PTB risk between the two groups was 3.1% (95% CI -7.6 to 13.8%), which was within the equivalence margin of 15%. The meta-analysis results showed no significant differences in the risk of PTB between the vaginal and IM progestogen treatments.

CONCLUSION

Compared with vaginal progesterone, treatment with intramuscular progestin might increase the risk of PTB before 37 weeks of gestation by as much as 13.8%, or reduce the risk by as much as 7.6%, in women with a history of spontaneous PTB or with short cervical length.

TWEETABLE ABSTRACT

Vaginal and intramuscular progestogen showed equivalent efficacy for preventing preterm birth before 37 weeks of gestation.

Maternal Serum Lipid Trajectories and Association with Pregnancy Loss and Length of Gestation

OBJECTIVE

We characterized lipid trajectories and investigated lipids and rate of pregnancy lipid change with the risk of pregnancy loss or preterm delivery <37 weeks.

STUDY DESIGN

In a secondary analysis of 337 women with one to two prior losses assigned to placebo in a randomized controlled trial at four centers (2007-2012), cholesterol, low- and high-density lipoprotein cholesterol (HDL-C), and triglycerides were measured up to 6 months prepregnancy (time 0) and pregnancy up to 7 visits. Trajectories were created using linear mixed models. Multivariable logistic regression with adjustment for maternal characteristics and cholesterol was performed.

RESULTS

Lipids decreased from prepregnancy to 4 to 5 weeks, followed by an increase, and were biphasic or triphasic depending on the lipid component. Between 4 and 8 weeks, for every 1-unit increase in HDL-C, there was a 22% decreased odds of loss <14 weeks (odds ratio: 0.78; 95% confidence interval: 0.60, 0.99) and 24% decreased odds of loss or preterm delivery 14 to <37 weeks (odds ratio: 0.76; 95% confidence interval: 0.60, 0.96).

CONCLUSION

There were no associations with other lipid components or other time points. An impaired rise of HDL-C early in pregnancy may signal maladaptation to pregnancy that is associated with pregnancy loss or preterm delivery.

Association of Medicaid Expansion With Coverage and Access to Care for Pregnant Women

OBJECTIVE

To identify the association of the Affordable Care Act's Medicaid expansion with payment for delivery, early access to prenatal care, preterm birth, and birth weights considered small for gestational age (SGA).

METHODS

A difference-in-difference design was used to assess changes in outcomes before and after Medicaid expansion in expansion states, using nonexpansion states as a control group. We used national birth certificate data from 2009 to 2017. Difference-in-difference linear probability models were used to assess the effects of the policy implementation, adjusting for demographics, month of birth, state, year, and county-level unemployment rates. Standard errors were clustered at the state level. Two prespecified subgroup analyses were performed of nulliparous women and women with no more than a high school diploma.

RESULTS

The study sample included 8,701,889 women from 15 expansion states and 9,509,994 from 11 nonexpansion states. In the adjusted analysis, the percentage of Medicaid-covered deliveries increased by 2.3 absolute percentage points (95% CI 0.2-4.4, P=.04) in expansion states compared with nonexpansion states. There were no significant changes in the proportion of women who were uninsured, as there was a relative decrease in the percentage of deliveries covered by private insurance (-2.8 percentage points [95% CI -4.9 to -0.8, P=.01]). There were also no significant differences in the rate of women initiating prenatal care in the first trimester, preterm birth rates, or rates of low birth weight after the Medicaid expansion. Findings were similar in both subgroups.

CONCLUSION

Medicaid expansion was associated with increased Medicaid coverage for childbirth in expansion states; similar gains in private coverage were seen in nonexpansion states. There were no associations with changes in early access to prenatal care, preterm birth, or SGA birth weights.

Robotic Transabdominal Cerclage vs Laparotomy: A Comparison of Obstetric and Surgical Outcomes

STUDY OBJECTIVE

To compare obstetric and surgical outcomes of transabdominal cerclage (TAC) via laparotomy (TAC-LAP) versus robotic-assisted (TAC-RA) approaches.

DESIGN

Retrospective cohort study.

SETTING

An academic medical center.

PATIENTS

Sixty-nine women with acquired or congenital cervical insufficiency.

INTERVENTIONS

All women underwent TAC either by laparotomy or robotic-assisted approaches by 2 primary surgeons between January 2003 and July 2018. Women with a preconceptional TAC without a subsequent pregnancy were excluded.

MEASUREMENTS AND MAIN RESULTS

A total of 69 women met inclusion criteria in the 15-year study period with 40 in the historical TAC-LAP group and 29 in the TAC-RA group. Gestational age at delivery was similar in the 2 groups (36 weeks 3 days vs 37 weeks; median difference -1 day, 95% confidence interval [CI] -6 to 2, p = .36). There were no differences in birth weight, Apgar scores, neonatal intensive care unit admission, or neonatal survival. Estimated blood loss and length of stay were significantly greater in the TAC-LAP group (50 mL vs 20 mL; median difference 25, 95% CI 5-40, p = .007 and 76 hours vs 3 hours; median difference 71, 95% CI 65-75, p <.001, respectively). Operative time was significantly shorter in the TAC-LAP group (65 minutes vs 132 minutes; median difference -64.7, 95% CI -79 to -49, p <.001). There was one intra-operative complication and 4 minor postoperative complications in the TAC-LAP group and none observed in the TAC-RA group. All outcomes were similar when comparing postconceptional TAC alone, except there was no longer a difference in blood loss. When comparing pre- versus postconceptional robotic TAC, there were no differences in surgical outcomes.

CONCLUSION

Robotic TAC has similar favorable obstetric outcomes to traditional laparotomy and is associated with reduced blood loss and shorter hospital stays. Despite longer operative times, the robotic group did not experience any intra-operative or postoperative complications, which speaks to the benefits of this minimally invasive approach to TAC.

Severe adverse maternal outcomes associated with chorioamnionitis

BACKGROUND

Chorioamnionitis complicates 1-5% of all pregnancies and is associated with substantial neonatal morbidity. Prolonged labor and increased use of labor induction may lead to increased rates of chorioamnionitis.

OBJECTIVE

We sought to quantify serious adverse maternal outcomes that are associated with chorioamnionitis in a contemporary population of live births in the state of Ohio.

STUDY DESIGN

We conducted a population-based retrospective cohort study of all live births in Ohio (2006-2015). Maternal demographic and obstetric outcomes, as reported on the US birth certificate, were compared between women with and without chorioamnionitis. Primary study outcomes were maternal intensive care unit admission and composite adverse maternal outcome (intensive care unit admission, blood product transfusion, unplanned hysterectomy, unplanned operation after delivery, or ruptured uterus). Multivariate logistic regression estimated the relative association of chorioamnionitis with maternal adverse outcomes.

RESULTS

Of 1,393,054 live births in Ohio over 10 years, 17,430 live births (1.3%) had chorioamnionitis. Women with chorioamnionitis had significantly higher rates of maternal intensive care unit admission (0.5% vs 0.1%; P<.001) and composite adverse outcome (5.0% vs 1.5%; P<.001) compared with those without chorioamnionitis. Even after adjustment for coexisting risks, chorioamnionitis was associated with 2- to 3-fold increased risk of composite adverse outcome, maternal intensive care unit admission, blood transfusion, ruptured uterus, and unplanned operation after delivery. Sensitivity analysis that excluded women who delivered by cesarean section revealed persistent significant associations between chorioamnionitis and adverse maternal outcomes. The rate of composite adverse outcomes was higher at earlier gestational ages. However, the relative risk increase of adverse outcome was more pronounced with advancing gestational age at delivery.

CONCLUSION

The frequency of severe adverse outcomes in pregnancies that are complicated with chorioamnionitis is high, with 1 in every 20 cases affected, and includes an almost 3-fold increased risk for maternal intensive care unit admission compared with patients without chorioamnionitis. Efforts to prevent and treat chorioamnionitis to minimize maternal risk could be an important area of focus in the reduction of the rate of severe maternal morbidity in the United States.

Use of Mueller matrix colposcopy in the characterization of cervical collagen anisotropy

Annually, about 15 million preterm infants are born in the world. Of these, due to complications resulting from their premature birth, about 1 million would die before the age of five. Since the high incidence of preterm birth (PTB) is partially due to the lack of effective diagnostic modalities, methodologies are needed to determine risk of PTB. We propose a noninvasive tool based on polarized light imaging aimed at measuring the organization of collagen in the cervix. Cervical collagen has been shown to remodel with the approach of parturition. We used a full-field Mueller matrix polarimetric colposcope to assess and compare cervical collagen content and structure in nonpregnant and pregnant women in vivo. Local collagen directional azimuth was used and a total of eight cervices were imaged.

Pregnancy after periviable birth: making the case for innovative delivery of interpregnancy care

Objective: Women who have had a spontaneous periviable delivery are at high risk for recurrent preterm delivery. The objective of our study was to determine interpregnancy interval (IPI) after periviable birth as well as percentage of women taking 17 alpha hydroxyprogesteronecaproate (17OHP-C) after periviable birth. We then examined the association between adherence with a postpartum visit after a periviable birth and IPI as well as receipt of 17OHP-C. Materials and methods: We included all women with a periviable delivery (20-26-week gestation) due to spontaneous preterm birth at Magee Women's Hospital between 2009 and 2014, who had their subsequent delivery at our institution during or before May of 2016. Information on maternal, fetal, and neonatal outcomes was obtained from the Magee Obstetrical Medical and Infant (MOMI) database as well as chart abstraction. We calculated IPI, proportion of women who received 17OHP-C in their next pregnancy, and attendance rates with a postpartum visit. The relationship between attendance with a postpartum visit and IPI, and receipt of 17OHP-C was examined with a logistic regression. Results: During the study period, 361 women had a spontaneous periviable birth. A total of 60 women had a subsequent delivery at Magee Women's Hospital. Only 33/60 (52.5%) presented for a postpartum visit after their periviable delivery. The median IPI for the cohort was 12.5 months (interquartile range: 6.4, 17.5 months) and 21.0% (n = 13) had an IPI less than 6 months. Adherence with the postpartum visit was not associated with an IPI less than 6 months. A total of 18.33% (11 women) did not receive 17OHP-C in their subsequent pregnancy. Women who attended a postpartum visit were much more likely to receive 17OHP-C (p = .001). Conclusions: Many women with a history of a periviable birth do not optimize strategies to reduce their risk of recurrent preterm birth. While attendance with a postpartum visit was associated with greater receipt of 17OHP-C in the subsequent pregnancy, given the overall poor rate of attendance with the postpartum visit in this cohort, novel strategies to counsel women about interpregnancy health are needed.

Cervical-length measurement in mid-gestation to predict spontaneous preterm birth in asymptomatic triplet pregnancy

OBJECTIVE

To assess the predictive value of sonographic cervical-length (CL) measurement in mid-gestation for spontaneous preterm birth (PTB) in asymptomatic triplet pregnancy.

METHODS

This was a retrospective study of asymptomatic triplet pregnancies followed at five Italian tertiary referral centers, between 2002 and 2015. CL was measured transvaginally between 18 and 24 weeks' gestation. Pregnancies with medically indicated PTB were excluded. Demographic and pregnancy characteristics of pregnancies complicated by PTB were analyzed and the distributions of CL measurements in these patients were calculated. Logistic regression analysis was performed to assess the association between CL and PTB, adjusted for confounders. Performance of CL measurement in prediction of PTB < 28, < 30 and < 32 weeks of gestation was assessed.

RESULTS

A total of 120 triplet pregnancies were included in the final analysis. Median CL was 35 (interquartile range (IQR), 29-40) mm measured at a median gestational age of 20 + 2 (IQR, 20 + 0 to 23 + 4) weeks. Overall, 23 (19.2%), 17 (14.2%) and eight (6.7%) patients had a CL < 25, < 20 and < 15 mm, respectively. Spontaneous PTB < 32 weeks occurred in 41 (34.2%) cases, < 30 weeks in 23 (19.2%) and < 28 weeks in 12 (10%) cases. CL < 15 mm was significantly more frequent in the group of patients who delivered < 28 (P = 0.03) and < 30 (P = 0.01) weeks' gestation, compared with those who delivered after 28 and after 30 weeks, respectively, while CL < 20 mm was more common in triplet pregnancies with delivery < 32 weeks compared with those delivered ≥ 32 weeks (P = 0.03). Logistic regression analysis was possible only for PTB < 32 weeks due to the small number of cases that delivered < 30 and < 28 weeks. After adjustment for confounders, CL was not significantly associated with PTB < 32 weeks (adjusted odds ratio, 0.97; 95% CI, 0.94-1.01). CL measurement had an area under the receiver-operating characteristics curve of 0.41 (95% CI, 0.20-0.62), 0.41 (95% CI, 0.26-0.56) and 0.42 (95% CI, 0.31-0.54) for the prediction of spontaneous PTB < 28, < 30 and < 32 weeks, respectively.

CONCLUSION

CL assessed in mid-gestation is a poor predictor of PTB < 28, < 30 and < 32 weeks' gestation in asymptomatic triplet pregnancy. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Mid-trimester sonographic cervical consistency index to predict spontaneous preterm birth in a low-risk population

OBJECTIVES

To investigate the effectiveness of mid-trimester sonographic cervical consistency index (CCI) for the prediction of spontaneous preterm birth (sPTB) in low-risk pregnancies and to compare its performance with that of mid-trimester sonographic cervical-length (CL) measurement.

METHODS

This was a prospective cohort study of women with a singleton pregnancy examined by ultrasound at 19 + 0 to 24 + 6 weeks' gestation. All women underwent transvaginal ultrasound examination of the cervix, but CCI and CL were measured, offline, only in women without a risk factor for sPTB. Staff and participants were blinded to CL and CCI results. CCI was obtained by calculating the ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest. The primary outcome was prediction of sPTB before 37 + 0 weeks. Receiver-operating characteristics (ROC) curves were produced and sensitivity and specificity were calculated for the optimal cut-off based on the ROC curve and for the 1^st , 5^th and 10^th centiles of CCI and CL. Intraclass correlation coefficients (ICC) and Bland-Altman plots were used to estimate intra- and interobserver agreement and reliability for measurement of CCI and CL.

RESULTS

Of the 749 women who underwent ultrasound examination of the cervix, 532 were included for analysis. The rates of sPTB before 37 + 0 and before 34 + 0 weeks were 4.1% (22/532) and 1.3% (7/532), respectively. The rates of short cervix < 25 mm and ≤ 20 mm were 0.9% (5/532) and 0.4% (2/532), respectively. The area under the ROC curve (AUC) with regard to predicting sPTB before 37 + 0 weeks was 0.84 (95% CI, 0.75-0.93) for CCI compared with 0.68 (95% CI, 0.56-0.81) for CL (P = 0.03). The optimal cut-off based on the ROC curve was 64.6% for CCI (sensitivity, 77.3%; specificity, 82.7%) and that for CL was 37.9 mm (sensitivity, 72.7%; specificity, 61.2%). The AUC with regard to predicting sPTB before 34 + 0 weeks was 0.87 (95% CI, 0.71-1.0) for CCI compared with 0.71 (95% CI, 0.47-0.94) for CL (P = 0.25). The optimal cut-off based on the ROC curve was 63.6% for CCI (sensitivity, 85.7%; specificity, 84.0%) and that for CL was 37.9 mm (sensitivity, 85.7%; specificity, 61.3%). Intraobserver ICC was > 0.90 both for CCI and CL, while interobserver ICC was 0.89 for CCI and 0.90 for CL.

CONCLUSIONS

Second-trimester CCI is a better predictor of sPTB < 37 weeks in low-risk pregnancies than is CL. External validation is needed as well as studies assessing the value of CCI as a screening tool in unselected and high-risk populations. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Screening for spontaneous preterm birth and resultant therapies to reduce neonatal morbidity and mortality: A review

Despite considerable effort aimed at decreasing the incidence of spontaneous preterm birth, it remains the leading cause of perinatal morbidity and mortality. Screening strategies are imperfect. Approaches used to identify women considered by historical factors to be low risk for preterm delivery (generally considered to be women with singleton pregnancies without a history of a previous preterm birth) as well as those at high risk for preterm birth (those with a previous preterm birth, short cervix, or multiple gestation) continue to evolve. Herein, we review the current evidence and approaches to screening women for preterm birth, and examine future directions for clinical practice. Further research is necessary to better identify at-risk women and provide evidence-based management.

Mid-Trimester Cervical Consistency Index and Cervical Length to Predict Spontaneous Preterm Birth in a High-Risk Population

Background  Short cervical length (CL) has not been shown to be adequate as a single predictor of spontaneous preterm birth (sPTB) in high-risk pregnancies. Objective  The objective of this study was to evaluate the performance of the mid-trimester cervical consistency index (CCI) to predict sPTB in a cohort of high-risk pregnancies and to compare the results with those obtained with the CL. Study Design  Prospective cohort study including high-risk singleton pregnancies between 19 ⁺⁰ and 24 ⁺⁶ weeks. The ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest was calculated offline to obtain the CCI. Results  Eighty-two high sPTB risk women were included. CCI (%) was significantly reduced in women who delivered <37 ⁺⁰ weeks compared with those who delivered at term, while CL was not. The area under the curve (AUC) of the CCI to predict sPTB <37 ⁺⁰ weeks was 0.73 (95% confidence interval [CI], 0.61-0.85), being 0.51 (95% CI, 0.35-0.67), p  = 0.03 for CL. The AUC of the CCI to predict sPTB <34 ⁺⁰ weeks was 0.68 (95% CI, 0.54-0.82), being 0.49 (95% CI, 0.29-0.69), p  = 0.06 for CL. Conclusion  CCI performed better than sonographic CL to predict sPTB. Due to the limited predictive capacity of these two measurements, other tools are still needed to better identify women at increased risk.

Computer modeling tools to understand the causes of preterm birth

The mechanical integrity of the soft tissue structures supporting the fetus may play a role in maintaining a healthy pregnancy and triggering the onset of labor. Currently, the level of mechanical loading on the uterus, cervix, and fetal membranes during pregnancy is unknown, and it is hypothesized that the over-stretch of these tissues contributes to the premature onset of contractility, tissue remodeling, and membrane rupture, leading to preterm birth. The purpose of this review article is to introduce and discuss engineering analysis tools to evaluate and predict the mechanical loads on the uterus, cervix, and fetal membranes. Here we will explore the potential of using computational biomechanics and finite element analysis to study the causes of preterm birth and to develop a diagnostic tool that can predict gestational outcome. We will define engineering terms and identify the potential engineering variables that could be used to signal an abnormal pregnancy. We will discuss the translational ability of computational models for the better management of clinical patients. We will also discuss the process of model validation and the limitations of these models. We will explore how we can borrow from parallel engineering fields to push the boundary of patient care so that we can work toward eliminating preterm birth.

Prevention of preterm birth: Novel interventions for the cervix

Preterm birth is the leading cause of neonatal mortality and morbidity worldwide. Spontaneous preterm birth is a complex, multifactorial condition in which cervical dysfunction plays an important role in some women. Current treatment options for cervical dysfunction include cerclage and supplemental progesterone. In addition, cervical pessary is being studied in research protocols. However, cerclage, supplemental progesterone and cervical pessary have well known limitations and there is a strong need for alternate treatment options. In this review, we discuss two novel interventions to treat cervical dysfunction: (1) injectable, silk protein-based biomaterials for cervical tissue augmentation (injectable cerclage) and (2) a patient-specific pessary. Three-dimensional computer simulation of the cervix is performed to provide a biomechanical rationale for the interventions. Further development of these novel interventions could lead to new treatment options for women with cervical dysfunction.

17-alpha hydroxyprogesterone caproate for preterm birth prevention: Where have we been, how did we get here, and where are we going?

Prematurity is a major public health problem in the United States and worldwide. Women with a history of a previous preterm birth are at high risk for recurrence. Progesterone is a key hormone involved in pregnancy maintenance. In general, progesterone is thought to maintain pregnancy through several closely linked mechanisms: (1) promotion of uterine quiescence, (2) inhibition of pro-inflammatory cells, and (3) immunosuppressive action. 17-Alpha hydroxyprogesterone caproate is currently the only medication approved to prevent recurrent preterm birth. The purpose of this review is to discuss the history of 17-alpha hydroxyprogesterone caproate use for recurrent preterm birth prevention, the rationale behind 17-alpha hydroxyprogesterone caproate administration, and current evidence-based indications for 17-alpha hydroxyprogesterone caproate use.

Conceptualizing pathways linking women's empowerment and prematurity in developing countries

BACKGROUND

Globally, prematurity is the leading cause of death in children under the age of 5. Many efforts have focused on clinical approaches to improve the survival of premature babies. There is a need, however, to explore psychosocial, sociocultural, economic, and other factors as potential mechanisms to reduce the burden of prematurity. Women's empowerment may be a catalyst for moving the needle in this direction. The goal of this paper is to examine links between women's empowerment and prematurity in developing settings. We propose a conceptual model that shows pathways by which women's empowerment can affect prematurity and review and summarize the literature supporting the relationships we posit. We also suggest future directions for research on women's empowerment and prematurity.

METHODS

The key words we used for empowerment in the search were "empowerment," "women's status," "autonomy," and "decision-making," and for prematurity we used "preterm," "premature," and "prematurity." We did not use date, language, and regional restrictions. The search was done in PubMed, Population Information Online (POPLINE), and Web of Science. We selected intervening factors-factors that could potentially mediate the relationship between empowerment and prematurity-based on reviews of the risk factors and interventions to address prematurity and the determinants of those factors.

RESULTS

There is limited evidence supporting a direct link between women's empowerment and prematurity. However, there is evidence linking several dimensions of empowerment to factors known to be associated with prematurity and outcomes for premature babies. Our review of the literature shows that women's empowerment may reduce prematurity by (1) preventing early marriage and promoting family planning, which will delay age at first pregnancy and increase interpregnancy intervals; (2) improving women's nutritional status; (3) reducing domestic violence and other stressors to improve psychological health; and (4) improving access to and receipt of recommended health services during pregnancy and delivery to help prevent prematurity and improve survival of premature babies.

CONCLUSIONS

Women's empowerment is an important distal factor that affects prematurity through several intervening factors. Improving women's empowerment will help prevent prematurity and improve survival of preterm babies. Research to empirically show the links between women's empowerment and prematurity is however needed.

Use of progesterone supplement therapy for prevention of preterm birth: review of literatures

Preterm birth (PTB) is one of the most common complications during pregnancy and it primarily accounts for neonatal mortality and numerous morbidities including long-term sequelae including cerebral palsy and developmental disability. The most effective treatment of PTB is prediction and prevention of its risks. Risk factors of PTB include history of PTB, short cervical length (CL), multiple pregnancies, ethnicity, smoking, uterine anomaly and history of curettage or cervical conization. Among these risk factors, history of PTB, and short CL are the most important predictive factors. Progesterone supplement therapy is one of the few proven effective methods to prevent PTB in women with history of spontaneous PTB and in women with short CL. There are 2 types of progesterone therapy currently used for prevention of PTB: weekly intramuscular injection of 17-alpha hydroxyprogesterone caproate and daily administration of natural micronized progesterone vaginal gel, vaginal suppository, or oral capsule. However, the efficacy of progesterone therapy to prevent PTB may vary depending on the administration route, form, dose of progesterone and indications for the treatment. This review aims to summarize the efficacy and safety of progesterone supplement therapy on prevention of PTB according to different indication, type, route, and dose of progesterone, based on the results of recent randomized trials and meta-analysis.

County-level Variation in Infant Mortality Reporting at Early Previable Gestational Ages

BACKGROUND

Infant mortality rate (IMR), or number of infant deaths per 1000 livebirths, varies widely across the US While fetal deaths are not included in this measure, reported infant deaths do include those delivered at previable gestations, or ≤20 weeks gestation. Variation in reporting of these events may have a significant impact on IMR estimates.

METHODS

This retrospective analysis used US National Center for Health Statistics 2007-2013 data from 2391 US counties. Counties were categorised by US region, demographic characteristics, and state-level fetal death reporting requirements. County percentage of fetal deaths among all 17-20 week fetal and infant deaths was evaluated using multivariable linear regression. County-level characteristics were then included in multivariable linear regression to determine the associated change in county IMR.

RESULTS

County percentage of deaths at 17-20 weeks reported as fetal ranged from 0% to 100% (mean 63.7%). Every 1 point increase in this percentage was associated with a 0.02 point decrease in county IMR (95% confidence interval (CI) 0.02, 0.03). When county IMRs were recalculated holding the percentage of fetal vs. infant deaths at 17-20 weeks constant at 63.7%, results suggest that the predicted gap in county IMR between Northeast and Midwest regions would narrow by 0.45 points.

CONCLUSIONS

Variable reporting of previable fetal and infant deaths may compromise the validity of county IMR comparisons. Improved consistency and accuracy of fetal and infant death reporting is warranted.

Bleeding during pregnancy is associated with familial preterm birth

PURPOSE

the purpose of this study is to identify risk factors for familial, likely genetically-determined, preterm birth.

MATERIALS AND METHODS

We performed a case-control study, enrolling 211 patients (103 cases and 108 controls). Cases delivered between 20 and 35 weeks gestation, with a prior preterm birth or first-degree relative born prematurely. Controls delivered between 37-42 weeks. Groups were compared using a comprehensive questionnaire validated by medical record. Multivariate logistic regression assessed risk factor associations.

RESULTS

Of cases, 30% reported bleeding during pregnancy compared with 5% of controls, adjusted odds ratio (adjOR) 9.0, 95%CI 3.31-24.47. Of cases that delivered at 20-28 weeks, 44.8% reported bleeding during pregnancy compared with 24.6% at 29-35 weeks, p = .04. Other associations were prior first-trimester miscarriage adjOR 2.55 (CI 1.21-5.35) or second-trimester miscarriage, adjOR 6.3 (CI 1.76-22.56).

CONCLUSIONS

Bleeding during pregnancy and prior miscarriage were significantly associated with familial preterm birth. The magnitude of effect for bleeding in pregnancy was higher with earlier preterm births. These associations warrant further investigation.

Use of Mueller matrix polarimetry and optical coherence tomography in the characterization of cervical collagen anisotropy

Preterm birth (PTB) presents a serious medical health concern throughout the world. There is a high incidence of PTB in both developed and developing countries ranging from 11% to 15%, respectively. Recent research has shown that cervical collagen orientation and distribution changes during pregnancy may be useful in predicting PTB. Polarization imaging is an effective means to measure optical anisotropy in birefringent materials, such as the cervix's extracellular matrix. Noninvasive, full-field Mueller matrix polarimetry (MMP) imaging methodologies, and optical coherence tomography (OCT) imaging were used to assess cervical collagen content and structure in nonpregnant porcine cervices. We demonstrate that the highly ordered structure of the nonpregnant porcine cervix can be observed with MMP. Furthermore, when utilized ex vivo, OCT and MMP yield very similar results with a mean error of 3.46% between the two modalities.

Applying Precision Public Health to Prevent Preterm Birth

Preterm birth (PTB) is one of the major health-care challenges of our time. Being born too early is associated with major risks to the child with potential for serious consequences in terms of life-long disability and health-care costs. Discovering how to prevent PTB needs to be one of our greatest priorities. Recent advances have provided hope that a percentage of cases known to be related to risk factors may be amenable to prevention; but the majority of cases remain of unknown cause, and there is little chance of prevention. Applying the principle of precision public health may offer opportunities previously unavailable. Presented in this article are ideas that may improve our abilities in the fields of studying the effects of migration and of populations in transition, public health programs, tobacco control, routine measurement of length of the cervix in mid-pregnancy by ultrasound imaging, prevention of non-medically indicated late PTB, identification of pregnant women for whom treatment of vaginal infection may be of benefit, and screening by genetics and other “omics.” Opening new research in these fields, and viewing these clinical problems through a prism of precision public health, may produce benefits that will affect the lives of large numbers of people.

Dydrogesterone and pre-term birth

Progestin supplementation appears to be a promising approach to both preventing initiation of pre-term labor and treating it once it is already established. Successful pregnancy depends on maternal tolerance of the fetal "semi-allograft". A protein called progesterone-induced blocking factor (PIBF), by inducing a Th2 dominant cytokine production mediates the immunological effects of progesterone. Over time, various attempts have been made to clarify the question, whether progestogens can contribute positively to either prevention or treatment of pre-term labor and birth. Dydrogesterone treatment of women at risk of pre-term delivery results in increased PIBF production and IL-10 concentrations, and lower concentrations of IFNγ and could be effective for prevention or treatment of pre-term labor. Further randomized studies are needed.

Meal frequency patterns and glycemic properties of maternal diet in relation to preterm delivery: Results from a large prospective cohort study

Background

Dietary habits are linked to high maternal glucose levels, associated with preterm delivery. The aim of this study was to examine the associations between meal frequency and glycemic properties of maternal diet in relation to preterm delivery.

Methods

This prospective cohort study included 66,000 women from the Norwegian Mother and Child Cohort Study (MoBa). Meal frequency and food intake data were obtained from a validated food frequency questionnaire during mid-pregnancy. Principal component factor analysis was used with a data-driven approach, and three meal frequency patterns were identified: “snack meal”, “main meal”, and “evening meal”. Pattern scores were ranked in quartiles. Glycemic index and glycemic load were estimated from table values. Intakes of carbohydrates, added sugar, and fiber were reported in grams per day and divided into quartiles. Gestational age was obtained from the Medical Birth Registry of Norway. Preterm delivery was defined as birth at <37 gestational weeks. A Cox regression model was used to assess associations with preterm delivery.

Results

After adjustments, the “main meal” pattern was associated with a reduced risk of preterm delivery, with hazard ratios (HRs) of 0.89 (95% confidence interval (CI): 0.80, 0.98) and 0.90 (95% CI: 0.81, 0.99) for the third and fourth quartiles, respectively, and p for trend of 0.028. This was mainly attributed to the group of women with BMI ≥25 kg/m², with HRs of 0.87 (95% CI: 0.79, 0.96) and 0.89 (95% CI: 0.80, 0.98) for the third and fourth quartiles, respectively, and p for trend of 0.010. There was no association between glycemic index, glycemic load, carbohydrates, added sugar, fiber, or the remaining meal frequency patterns and preterm delivery.

Conclusion

Regular consumption of main meals (breakfast, lunch, dinner) was associated with a lower risk of preterm delivery. Diet should be further studied as potential contributing factors for preterm delivery.

Preterm Birth: Analysis of Longitudinal Data on Siblings Based on Random-Effects Logit Models

INTRODUCTION

The literature about the determinants of a preterm birth is still controversial. We approach the analysis of these determinants distinguishing between woman's observable characteristics, which may change over time, and unobservable woman's characteristics, which are time invariant and explain the dependence between the typology (normal or preterm) of consecutive births.

METHODS

We rely on a longitudinal dataset about 28,603 women who delivered for the first time in the period 2005-2013 in the Umbria Region (Italy). We consider singleton physiological pregnancies originating from natural conceptions with birthweight of at least 500 g and gestational age between 24 and 42 weeks; the overall number of deliveries is 34,224. The dataset is based on the Standard Certificates of Life Birth collected in the region in the same period. We estimate two types of logit model for the event that the birth is preterm. The first model is pooled and accounts for the information about possible previous preterm deliveries, including the lagged response among the covariates. The second model takes explicitly into account the longitudinal structure of data through the introduction of a random effect that summarizes all the (time invariant) unobservable characteristics of a woman affecting the probability of a preterm birth.

RESULTS

The estimated models provide evidence that the probability of a preterm birth depends on certain woman's demographic and socioeconomic characteristics, other than on the previous history in terms of miscarriages and the baby's gender. Besides, as the random-effects model fits significantly better than the pooled model with lagged response, we conclude for a spurious state dependence between repeated preterm deliveries.

CONCLUSION

The proposed analysis represents a useful tool to detect profiles of women with a high risk of preterm delivery. Such profiles are detected taking into account observable woman's demographic and socioeconomic characteristics as well as unobservable and time-constant characteristics, possibly related to the woman's genetic makeup.

TRIAL REGISTRATION

Not applicable.