Genetic studies of gestational duration and preterm birth

Recent Advances in Genomic Studies of Gestational Duration and Preterm Birth

Preterm birth (PTB) is the leading cause of infant mortality and morbidity. For several decades, extensive epidemiologic and genetic studies have highlighted the significant contribution of maternal and offspring genetic factors to PTB. This review discusses the challenges inherent in conventional genomic analyses of PTB and underscores the importance of adopting nonconventional approaches, such as analyzing the mother-child pair as a single analytical unit, to disentangle the intertwined maternal and fetal genetic influences. We elaborate on studies investigating PTB phenotypes through 3 levels of genetic analyses: single-variant, multi-variant, and genome-wide variants.

Linking Adverse Experiences to Pregnancy and Birth Outcomes: A Life Course Analysis of Racial and Ethnic Disparities Among Low-Income Women

Racial and ethnic disparities in birth outcomes have persisted in the United States for decades, though the causes remain poorly understood. The life course perspective posits that poorer outcomes of Black birthing people stem from heightened exposure to stressors early in life and cumulative exposure to stressors over time. Despite its prominence, this perspective has seldom been investigated empirically. We analyzed longitudinal data gathered from 1319 women in low-income households in Wisconsin who received perinatal home visiting services. Variable- and person-centered analyses were performed to assess whether 15 adverse childhood experiences (ACEs) and 10 adverse adult experiences (AAEs) were associated, alone and in combination, with pregnancy loss, preterm birth, and low birth weight among Hispanic (i.e., Latinx) and non-Hispanic Black and White participants. As expected, there were disparities in preterm birth and low birth weight, and both ACEs and AAEs were linked to poorer pregnancy and birth outcomes. Unexpectedly, bivariate and multivariate analyses showed that the associated effects of ACEs and AAEs were most robust for non-Hispanic White women. A latent class analysis produced four patterns of life course adversity, and multigroup latent class analyses confirmed that, compared to White women, higher-adversity class assignments were associated with less robust effects for Hispanic women, and even less robust effects for Black women. We discuss interpretations of the paradoxical findings, including the possibility that alternative sources of stress such as interpersonal and structural racism may better account for the reproductive disparities that disproportionately affect Black birthing people.

A Scoping Review of Preterm Birth Risk Factors

Preterm birth is a major cause of neonatal morbidity and mortality, but its etiology and risk factors are poorly understood. We undertook a scoping review to illustrate the breadth of risk factors for preterm birth that have been reported in the literature. We conducted a search in the PubMed database for articles published in the previous 5 years. We determined eligibility for this scoping review by screening titles and abstracts, followed by full-text review. We extracted odds ratios and other measures of association for each identified risk factor in the articles. A total of 2,509 unique articles were identified from the search, of which 314 were eligible for inclusion in our final analyses. We summarized risk factors and their relative impacts in the following categories: Activity, Psychological, Medical History, Toxicology, Genetics, and Vaginal Microbiome. Many risk factors for preterm birth have been reported. It is challenging to synthesize findings given the multitude of isolated risk factors that have been studied, inconsistent definitions of risk factors and outcomes, and use of different covariates in analyses. Novel methods of analyzing large datasets may promote a more comprehensive understanding of the etiology of preterm birth and ability to predict the outcome. KEY POINTS: · Preterm birth is difficult to predict.. · Preterm birth has many diverse risk factors.. · Holistic approaches may yield new insights..

Childbirth experiences of women with a history of physical, sexual, and child abuse: a cross-sectional study of 2,575 Russian women

BACKGROUND

A substantial number of women who subsequently become pregnant and give birth have a history of physical, sexual, and/or child abuse. This study investigated the associations of these types of traumas and their cumulative effect with childbirth experiences, namely, mode of birth, maternal and child complications during pregnancy/childbirth, preterm birth, medical procedures, and obstetric violence during labour.

METHODS

A group of Russian women (n = 2,575) who gave birth within the previous 12 months, completed a web-based survey, where they provided demographic information, details about their childbirth experiences, and a history of trauma.

RESULTS

Women with any type of past abuse were at higher risk for maternal complications during pregnancy/childbirth (exp(β) < 0.73, p < 0.010 for all). More specific to the type of trauma were associations of physical abuse with caesarean birth, child abuse with complications during pregnancy/childbirth for the baby, and physical and child abuse with obstetric violence (exp(β) < 0.54, p < 0.022 for all). There was a cumulative effect of trauma for all the outcomes except for medical procedures during childbirth and preterm birth.

CONCLUSION

This study provides insights into potential different individual effects of physical, sexual, and/or child abuse as well as their cumulative impact on the childbirth experiences. The robust findings about maternal complications during pregnancy/childbirth and obstetric violence highlight the importance of trauma-informed care, supportive policies, and interventions to create safe and empowering birthing environments that prioritise patient autonomy, dignity, and respectful communication.

African immigrants' favorable preterm birth rates challenge genetic etiology of the Black-White disparity in preterm birth

Background

We examined over a million California birth records for 2010 through 2021 to investigate whether disparities in preterm birth (PTB) by nativity and race support the widely held but hitherto unsubstantiated belief that genetic differences explain the persistent Black-White disparity in PTB.

Methods

We examined PTB rates and risk ratios among African-, Caribbean-, and U.S.-born Black women compared to U.S.-born White women. Multivariate analyses adjusted for maternal age, education, number of live births, delivery payer, trimester of prenatal care initiation, pre-pregnancy BMI, smoking, and prevalence of poverty in a woman's residence census tract; and for paternal education.

Results

In adjusted analyses, African-born Black women's PTB rates were no different from those of U.S.-born White women.

Discussion

The results add to prior evidence making a genetic etiology for the racial disparity in PTB unlikely. If genetic differences tied to "race" explained the Black-White disparity in PTB among U.S.-born women, the African immigrants in this study would have had higher rates of PTB, not the lower rates observed. Multiple explanations for the observed patterns and their implications are discussed. Failure to distinguish causes of PTB from causes of the racial disparity in PTB have likely contributed to erroneous attribution of the racial disparity to genetic differences. Based on the literature, unmeasured experiences of racism, including racism-related stress and adverse environmental exposures, are plausible explanations for the PTB disparity between Black and White U.S.-born women. The favorable birth outcomes of African-born Black immigrants may reflect less exposure to racism during sensitive life periods, e.g., childhood, when they were in African countries, where Black people are in the racial majority.

Genetic association study of Preterm birth and Gestational age in a population-based case-control study in Peru

Preterm birth (PTB) is an adverse pregnancy outcome affecting ∼15 million pregnancies worldwide. Genetic studies have identified several candidate loci for PTB, but results remain inconclusive and limited to European populations. Thus, we conducted a genome-wide association study (GWAS) of PTB and gestational age at delivery (GA) among 2,212 Peruvian women. PTB cases delivered ≥ 20 weeks' but < 37 weeks' gestation, while controls delivered at term (≥ 37 weeks but < 42 weeks). After imputation (TOPMED) and quality control, we assessed the association of ∼6 million SNPs with PTB and GA using multivariable regression models adjusted for maternal age and the first two genetic principal components. In silico functional analysis (FUMA-GWAS) was conducted among top signals detected with an arbitrary P < 1.0×10 -5 in each GWAS. We sought to replicate genetic associations with PTB and GA identified in Europeans, and we developed a genetic risk score for GA based on European markers. Mean GA was 30 ± 4 weeks in PTB cases (N=933) and 39 ± 1 in the controls (N=1,279). PTB cases were slightly older and had higher C-sections and vaginal bleeding than controls. No association was identified at genome-wide level. Top suggestive ( P < 1.0×10 -5 ) signals were seen at rs13151645 ( LINC01182 ) for PTB, and at rs72824565 ( CTNNA2 ) for GA. Top PTB variants were enriched for biological pathways associated with polyketide, progesterone, steroid hormones, and glycosyl metabolism. Top GA variants were enriched in intronic regions and cancer pathways, and these genes were upregulated in the brain and subcutaneous adipose tissue. In combination with non-genetic risk factors, top SNPs explained 14% and 15% of the phenotypic variance of PTB and GA in our sample, but these results need to be interpreted with caution. Variants in WNT4 associated with GA in Europeans were replicated in our study. The genetic risk score based in European markers, was associated with a 2-day longer GA (R 2 =0.003, P =0.002) per standard deviation increase in the score in our sample. This genetic association study identified various signals suggestively associated with PTB and GA in a non- European population; they were linked to relevant biological pathways related to the metabolism of progesterone, prostanoid, and steroid hormones, and genes associated with GA were significantly upregulated in relevant tissues for the pathophysiology of PTB based on the in- silico functional analysis. None of these top variants overlapped with signals previously identified for PTB or GA in Europeans.

Why Causation Matters: Rethinking "Race" as a Risk Factor

Although it is tempting to construe the correlation between Black "race" and higher rates of preterm birth as causal, this logic is flawed. Worse, the continued use of Black "race" as a risk factor for preterm birth is actively harmful. Using Black "race" as a risk factor suggests a causal relationship that does not exist and, critically, obscures what actually causes Black patients to be more vulnerable to poorer maternal and infant outcomes: anti-Black racism. Failing to name anti-Black racism as the root cause of Black patients' vulnerability conceals key pathways and tempts us to construe Black "race" as immutably related to higher rates of preterm birth. The result is that we overlook two highly treatable pathways-chronic stress and implicit bias-through which anti-Black racism negatively contributes to birth. Thus, clinicians may underuse important tools to reduce stress from racism and discrimination while missing opportunities to address implicit bias within their practices and institutions. Fortunately, researchers, physicians, clinicians, and medical staff can positively affect Black maternal and infant health by shifting our causal paradigm. By eliminating the use of Black "race" as a risk factor and naming anti-Black racism as the root cause of Black patients' vulnerability, we can practice anti-racist maternity care and take a critical step toward achieving birth equity.

A functional mechanism for a non-coding variant near AGTR2 associated with risk for preterm birth

BACKGROUND

Preterm birth (PTB), defined as delivery before 37 gestational weeks, imposes significant public health burdens. A recent maternal genome-wide association study of spontaneous PTB identified a noncoding locus near the angiotensin II receptor type 2 (AGTR2) gene. Genotype-Tissue Expression data revealed that alleles associated with decreased AGTR2 expression in the uterus were linked to an increased risk of PTB and shortened gestational duration. We hypothesized that a causative variant in this locus modifies AGTR2 expression by altering transcription factor (TF) binding.

METHODS

To investigate this hypothesis, we performed bioinformatics analyses and functional characterizations at the implicated locus. Potential causal single nucleotide polymorphisms (SNPs) were prioritized, and allele-dependent binding of TFs was predicted. Reporter assays were employed to assess the enhancer activity of the top PTB-associated non-coding variant, rs7889204, and its impact on TF binding.

RESULTS

Our analyses revealed that rs7889204, a top PTB-associated non-coding genetic variant is one of the strongest eQTLs for the AGTR2 gene in uterine tissue samples. We observed differential binding of CEBPB (CCAAT enhancer binding protein beta) and HOXA10 (homeobox A10) to the alleles of rs7889204. Reporter assays demonstrated decreased enhancer activity for the rs7889204 risk "C" allele.

CONCLUSION

Collectively, these results demonstrate that decreased AGTR2 expression caused by reduced transcription factor binding increases the risk for PTB and suggest that enhancing AGTR2 activity may be a preventative measure in reducing PTB risk.

Past Traumatic Life Events, Postpartum PTSD, and the Role of Labor Support

The aim of this study was to investigate the association of postpartum post-traumatic stress disorder (PP-PTSD) symptoms and subjective rates of traumatic birth experience with past traumatic life events (physical and sexual assault, child abuse, perinatal loss, previous traumatic birth experience, and the cumulative traumatic experience). A sample of Russian women (n = 2579) who gave birth within the previous 12 months, filled in a web-based survey, where they reported demographic and obstetric characteristics and past traumatic experiences, evaluated their birth experience (0 = not traumatic, 10 = extremely traumatic), and completed the City Birth Trauma Scale (CBiTS). We found that PP-PTSD symptoms were higher among women who previously experienced physical (F = 22.02, p < 0.001) and sexual (F = 15.98, p < 0.001) assault and child abuse (F = 69.25, p < 0.001), with only associations with child abuse (F = 21.14, p < 0.001) remaining significant for subjective rates of traumatic birth experience. Perinatal loss and previous traumatic birth showed moderate but inconsistent effects. Support during labor did not have a buffering effect for participants with past traumatic experiences but showed a universally protective effect against PP-PTSD. Trauma-informed practices and allowing women to have a supportive birth team of choice during childbirth are promising avenues to minimize the incidence of PP-PTSD and improve the childbirth experience for all women.

Ultra-low-coverage genome-wide association study-insights into gestational age using 17,844 embryo samples with preimplantation genetic testing

BACKGROUND

Very low-coverage (0.1 to 1×) whole genome sequencing (WGS) has become a promising and affordable approach to discover genomic variants of human populations for genome-wide association study (GWAS). To support genetic screening using preimplantation genetic testing (PGT) in a large population, the sequencing coverage goes below 0.1× to an ultra-low level. However, the feasibility and effectiveness of ultra-low-coverage WGS (ulcWGS) for GWAS remains undetermined.

METHODS

We built a pipeline to carry out analysis of ulcWGS data for GWAS. To examine its effectiveness, we benchmarked the accuracy of genotype imputation at the combination of different coverages below 0.1× and sample sizes from 2000 to 16,000, using 17,844 embryo PGT samples with approximately 0.04× average coverage and the standard Chinese sample HG005 with known genotypes. We then applied the imputed genotypes of 1744 transferred embryos who have gestational ages and complete follow-up records to GWAS.

RESULTS

The accuracy of genotype imputation under ultra-low coverage can be improved by increasing the sample size and applying a set of filters. From 1744 born embryos, we identified 11 genomic risk loci associated with gestational ages and 166 genes mapped to these loci according to positional, expression quantitative trait locus, and chromatin interaction strategies. Among these mapped genes, CRHBP, ICAM1, and OXTR were more frequently reported as preterm birth related. By joint analysis of gene expression data from previous studies, we constructed interrelationships of mainly CRHBP, ICAM1, PLAGL1, DNMT1, CNTLN, DKK1, and EGR2 with preterm birth, infant disease, and breast cancer.

CONCLUSIONS

This study not only demonstrates that ulcWGS could achieve relatively high accuracy of adequate genotype imputation and is capable of GWAS, but also provides insights into the associations between gestational age and genetic variations of the fetal embryos from Chinese population.

Genetics, epigenetics, and transcriptomics of preterm birth

Preterm birth contributes significantly to neonatal mortality and morbidity. Despite its global significance, there has only been limited progress in preventing preterm birth. Spontaneous preterm birth (sPTB) results from a wide variety of pathological processes. Although many non-genetic risk factors influence the timing of gestation and labor, compelling evidence supports the role of substantial genetic and epigenetic influences and their interactions with the environment contributing to sPTB. To investigate a common and complex disease such as sPTB, various approaches such as genome-wide association studies, whole-exome sequencing, transcriptomics, and integrative approaches combining these with other 'omics studies have been used. However, many of these studies were typically small or focused on a single ethnicity or geographic region with limited data, particularly in populations at high risk for sPTB, or lacked a robust replication. These studies found many genes involved in the inflammation and immunity-related pathways that may affect sPTB. Recent studies also suggest the role of epigenetic modifications of gene expression by the environmental signals as a potential contributor to the risk of sPTB. Future genetic studies of sPTB should continue to consider the contributions of both maternal and fetal genomes as well as their interaction with the environment.

Human placental proteomics and exon variant studies link AAT/SERPINA1 with spontaneous preterm birth

BACKGROUND

Preterm birth is defined as live birth before 37 completed weeks of pregnancy, and it is a major problem worldwide. The molecular mechanisms that lead to onset of spontaneous preterm birth are incompletely understood. Prediction and evaluation of the risk of preterm birth is challenging as there is a lack of accurate biomarkers. In this study, our aim was to identify placental proteins that associate with spontaneous preterm birth.

METHODS

We analyzed the proteomes from placentas to identify proteins that associate with both gestational age and spontaneous labor. Next, rare and potentially damaging gene variants of the identified protein candidates were sought for from our whole exome sequencing data. Further experiments we performed on placental samples and placenta-associated cells to explore the location and function of the spontaneous preterm labor-associated proteins in placentas.

RESULTS

Exome sequencing data revealed rare damaging variants in SERPINA1 in families with recurrent spontaneous preterm deliveries. Protein and mRNA levels of alpha-1 antitrypsin/SERPINA1 from the maternal side of the placenta were downregulated in spontaneous preterm births. Alpha-1 antitrypsin was expressed by villous trophoblasts in the placenta, and immunoelectron microscopy showed localization in decidual fibrinoid deposits in association with specific extracellular proteins. siRNA knockdown in trophoblast-derived HTR8/SVneo cells revealed that SERPINA1 had a marked effect on regulation of the actin cytoskeleton pathway, Slit-Robo signaling, and extracellular matrix organization.

CONCLUSIONS

Alpha-1 antitrypsin is a protease inhibitor. We propose that loss of the protease inhibition effects of alpha-1 antitrypsin renders structures critical to maintaining pregnancy susceptible to proteases and inflammatory activation. This may lead to spontaneous premature birth.

Differences in risk factors for incident and recurrent preterm birth: a population-based linkage of 3.5 million births from the CIDACS birth cohort

BACKGROUND

Preterm birth (PTB) is a syndrome resulting from a complex list of underlying causes and factors, and whether these risk factors differ in the context of prior PTB history is less understood. The aim of this study was to explore whether PTB risk factors in a second pregnancy were different in women with versus without previous PTB.

METHODS

We conducted a population-based cohort study using data from the birth cohort of the Center for Data and Knowledge Integration for Health (CIDACS) for the period 2001 to 2015. We used longitudinal transition models with multivariate logistic regression to investigate whether risk factors varied between incident and recurrent PTB.

RESULTS

A total of 3,528,050 live births from 1,764,025 multiparous women were analyzed. We identified different risk factors (P_difference <0.05) between incident and recurrent PTB. The following were associated with an increased chance for PTB incidence, but not recurrent: household overcrowding (OR 1.09), maternal race/ethnicity [(Black/mixed-OR 1.04) and (indigenous-OR 1.34)], young maternal age (14 to 19 years-OR 1.16), and cesarean delivery (OR 1.09). The following were associated with both incident and recurrent PTB, respectively: single marital status (OR 0.85 vs 0.90), reduced number of prenatal visits [(no visit-OR 2.56 vs OR 2.16) and (1 to 3 visits-OR 2.44 vs OR 2.24)], short interbirth interval [(12 to 23 months-OR 1.04 vs OR 1.22) and (<12 months, OR 1.89, 95 vs OR 2.58)], and advanced maternal age (35-49 years-OR 1.42 vs OR 1.45). For most risk factors, the point estimates were higher for incident PTB than recurrent PTB.

CONCLUSIONS

The risk factors for PTB in the second pregnancy differed according to women's first pregnancy PTB status. The findings give the basis for the development of specific prevention strategies for PTB in a subsequent pregnancy.

Maternal childhood maltreatment and perinatal outcomes: A systematic review

BACKGROUND

Maternal childhood maltreatment (MCM) is linked to poor perinatal outcomes but the evidence base lacks cohesion. We explore the impact of MCM on four perinatal outcome domains: pregnancy and obstetric; maternal mental health; infant; and the quality of the care-giving environment. Mechanisms identified in the included studies are discussed in relation to the maternal programming hypothesis and directions for future research.

METHOD

We completed a comprehensive literature search of eight electronic databases. Independent quality assessments were conducted and PRISMA protocols applied to data extraction.

RESULTS

Inclusion criteria was met by N = 49 studies. MCM was consistently associated with difficulties in maternal and infant emotional regulation and with disturbances in the mother-infant relationship. Directly observed and maternal-reported difficulties in the mother-infant relationship were often mediated by mothers' current symptoms of psychopathology. Direct and mediated associations between MCM and adverse pregnancy and obstetric outcomes were suggested by a limited number of studies. Emotional and sexual abuse were the most consistent MCM subtype significantly associated with adverse perinatal outcomes.

LIMITATIONS

A meta-analysis was not possible due to inconsistent reporting and the generally small number of studies for most perinatal outcomes.

CONCLUSIONS

MCM is associated with adverse perinatal outcomes for mothers' and infants. Evidence suggests these associations are mediated by disruptions to maternal emotional functioning. Future research should explore biological and psychosocial mechanisms underpinning observed associations between specific subtypes of MCM and adverse perinatal outcomes. Services have a unique opportunity to screen for MCM and detect women and infants at risk of adverse outcomes during the perinatal period.

Recurrent preterm birth risk assessment for two delivery subtypes: A multivariable analysis

OBJECTIVE

The study sought to develop and apply a framework that uses a clinical phenotyping tool to assess risk for recurrent preterm birth.

MATERIALS AND METHODS

We extended an existing clinical phenotyping tool and applied a 4-step framework for our retrospective cohort study. The study was based on data collected in the Genomic and Proteomic Network for Preterm Birth Research Longitudinal Cohort Study (GPN-PBR LS). A total of 52 sociodemographic, clinical and obstetric history-related risk factors were selected for the analysis. Spontaneous and indicated delivery subtypes were analyzed both individually and in combination. Chi-square analysis and Kaplan-Meier estimate were used for univariate analysis. A Cox proportional hazards model was used for multivariable analysis.

RESULTS

: A total of 428 women with a history of spontaneous preterm birth qualified for our analysis. The predictors of preterm delivery used in multivariable model were maternal age, maternal race, household income, marital status, previous caesarean section, number of previous deliveries, number of previous abortions, previous birth weight, cervical insufficiency, decidual hemorrhage, and placental dysfunction. The models stratified by delivery subtype performed better than the naïve model (concordance 0.76 for the spontaneous model, 0.87 for the indicated model, and 0.72 for the naïve model).

DISCUSSION

The proposed 4-step framework is effective to analyze risk factors for recurrent preterm birth in a retrospective cohort and possesses practical features for future analyses with other data sources (eg, electronic health record data).

CONCLUSIONS

We developed an analytical framework that utilizes a clinical phenotyping tool and performed a survival analysis to analyze risk for recurrent preterm birth.

Risk of chronic kidney disease in women with a history of preterm delivery: Tehran Lipid and Glucose Study

BACKGROUND

Preterm delivery (PTD) may predict the risk of long-term maternal complications. Little is known about the association between preterm delivery and maternal risk of chronic kidney disease (CKD).This study aimed to explore whether a history of preterm delivery is associated with the risk of maternal CKD.

METHODS

In this population-based cohort study within the framework of the Tehran Lipid and Glucose Study (TLGS), a total of 3035 women with at least one delivery met our eligibility criteria. A time-dependent Cox proportional-hazards regression model was used to measure the hazard ratios (HRs) and 95% confidence intervals (CIs) for evaluating the association between history of preterm delivery and risk of CKD, adjusted for smoking, parity, age at first delivery, body mass index, educational level, preeclampsia, and gestational diabetes mellitus.

RESULTS

A total of 212 women with a history of at least one preterm delivery and 2823 women with term delivery were included. The median (interquartile range) follow-up in the preterm and term delivery groups was 16 (13.0-17.0) and 16 (14.0-17.0) years, respectively. The results of multivariate Cox regression model, adjusted for confounders, showed that the risk of CKD significantly increased by 46% in women with a history of preterm delivery. Moreover, according to the time-dependent Cox regression analysis, the risk of CKD in women with a history of preterm delivery was 2.68 (95% CI 1.02, 7.05, P = 0.04) fold higher than among those with no history of  preterm delivery.

CONCLUSION

Pregnancy if complicated by preterm delivery, may increase the risk of future maternal morbidities. Our findings suggest that a history of preterm delivery was associated with an increased maternal risk of CKD in the long term. Further longitudinal studies are needed to confirm our findings.

Vaginal bacterial load in the second trimester is associated with early preterm birth recurrence: a nested case-control study

OBJECTIVE

To assess the association between vaginal microbiome (VMB) composition and recurrent early spontaneous preterm birth (sPTB)/preterm prelabour rupture of membranes (PPROM).

DESIGN

Nested case-control study.

SETTING

UK tertiary referral hospital.

SAMPLE

High-risk women with previous sPTB/PPROM <34⁺⁰  weeks' gestation who had a recurrence (n = 22) or delivered at ≥37⁺⁰  weeks without PPROM (n = 87).

METHODS

Vaginal swabs collected between 15 and 22 weeks' gestation were analysed by 16S rRNA gene sequencing and 16S quantitative PCR.

MAIN OUTCOME MEASURE

Recurrent early sPTB/PPROM.

RESULTS

Of the 109 high-risk women, 28 had anaerobic vaginal dysbiosis, with the remainder dominated by lactobacilli (Lactobacillus iners 36/109, Lactobacillus crispatus 23/109, or other 22/109). VMB type and diversity were not associated with recurrence. Women with a recurrence, compared to those without, had a higher median vaginal bacterial load (8.64 versus 7.89 log₁₀ cells/mcl, adjusted odds ratio [aOR] 1.90, 95% CI 1.01-3.56, P = 0.047) and estimated Lactobacillus concentration (8.59 versus 7.48 log₁₀ cells/mcl, aOR 2.35, (95% CI 1.20-4.61, P = 0.013). A higher recurrence risk was associated with higher median bacterial loads for each VMB type after stratification, although statistical significance was reached only for L. iners domination (aOR 3.44, 95% CI 1.06-11.15, P = 0.040). Women with anaerobic dysbiosis or L. iners domination had a higher median vaginal bacterial load than women with a VMB dominated by L. crispatus or other lactobacilli (8.54, 7.96, 7.63, and 7.53 log₁₀ cells/mcl, respectively).

CONCLUSIONS

Vaginal bacterial load is associated with early sPTB/PPROM recurrence. Domination by lactobacilli other than L. iners may protect women from developing high bacterial loads. Future PTB studies should quantify vaginal bacteria and yeasts.

TWEETABLE ABSTRACT

Increased vaginal bacterial load in the second trimester may be associated with recurrent early spontaneous preterm birth.

Inflammatory factors, genetic variants, and predisposition for preterm birth

Preterm birth is a major clinical and public health challenge, with a prevalence of 11% worldwide. It is the leading cause of death in children younger than 5 years old and represents 70% of neonatal deaths and 75% of neonatal morbidity. Despite the clinical and public health significance, this condition's etiology is still unclear, and most of the cases are spontaneous. There are several known preterm birth risk factors, including inflammatory diseases and the genetic background, although the underlying molecular mechanisms are far from understood. The present review highlights the research advances on the association between inflammatory-related genes and the increased risk for preterm delivery. The most associated genetic variants are the TNFα rs1800629, the IL1α rs17561, and the IL1RN rs2234663. Moreover, many of the genes discussed in this review are also implicated in pathologies involving inflammatory or autoimmune systems, such as periodontal disease, bowel inflammatory disease, and autoimmune rheumatic diseases. This review presents evidence suggesting a common genetic background to preterm birth, autoimmune and inflammatory diseases susceptibility.

Clinical, Immunologic and Molecular Spectrum of Patients with Immunodeficiency, Centromeric Instability, and Facial Anomalies (ICF) Syndrome: A Systematic Review

BACKGROUND

Immunodeficiency, centromeric instability and facial dysmorphism (ICF) syndrome is a rare autosomal recessive immune disorder presenting with hypogammaglobulinemia, developmental delay, and facial anomalies. The ICF type 1, type 2, type 3 and type 4 are characterized by mutations in DNMT3B, ZBTB24, CDCA7 or HELLS gene, respectively. This study aimed to present a comprehensive description of the clinical, immunologic and genetic features of patients with ICF syndrome.

METHODS

PubMed, Web of Science, and Scopus were searched systemically to find eligible studies.

RESULTS

Forty-eight studies with 118 ICF patients who met the inclusion criteria were included in our study. Among these patients, 60% reported with ICF-1, 30% with ICF-2, 4% with ICF-3, and 6% with ICF-4. The four most common symptoms reported in patients with ICF syndrome were: delay in motor development, low birth weight, chronic infections, and diarrhea. Intellectual disability and preterm birth among patients with ICF-2 and failure to thrive, sepsis and fungal infections among patients with ICF-1 were also more frequent. Moreover, the median levels of all three immunoglobulins (IgA, IgG, IgM) were markedly reduced within four types of ICF syndrome.

CONCLUSION

The frequency of diagnosed patients with ICF syndrome has increased. Early diagnosis of ICF is important since immunoglobulin supplementation or allogeneic stem cell transplantation can improve the disease-free survival rate.

Mediterranean-Style Diet and Birth Outcomes in an Urban, Multiethnic, and Low-Income US Population

Findings on the role of Mediterranean-style diet (MSD) on duration of pregnancy and birth weight have been inconsistent and based largely on Non-Hispanic white populations, making it unclear as to whether they could extend to African Americans who are at a higher risk of unfavorable birth outcomes. Our study addresses this gap using a large urban, multiethnic, predominantly low-income cohort of mother-infant dyads from Boston, MA, USA. Dietary information was obtained via food frequency questionnaires; health information including birth outcomes were extracted from medical records. A Mediterranean-style diet score (MSDS) was formulated based on intake history, and linear and log-binomial regressions were performed to assess its association with birth outcomes. After adjustment, the lowest MSDS quintile from the overall sample was found to be associated with an increased relative risk (RR) of overall preterm birth (RR 1.18; 95% CI: 1.06-1.31), spontaneous preterm birth (1.28; 1.11-1.49), late preterm birth (1.21; 1.05-1.39), and low birth weight (1.11; 1.01-1.22), compared to the highest quintile. The findings were similar for the African American sample. Our study adds to the current understanding of the diet's influence on birth outcomes by demonstrating that adherence to MSD may improve birth outcomes for African American women.

Predictors of singleton preterm birth using multinomial regression models accounting for missing data: A birth registry-based cohort study in northern Tanzania

BACKGROUND

Preterm birth is a significant contributor of under-five and newborn deaths globally. Recent estimates indicated that, Tanzania ranks the tenth country with the highest preterm birth rates in the world, and shares 2.2% of the global proportion of all preterm births. Previous studies applied binary regression models to determine predictors of preterm birth by collapsing gestational age at birth to <37 weeks. For targeted interventions, this study aimed to determine predictors of preterm birth using multinomial regression models accounting for missing data.

METHODS

We carried out a secondary analysis of cohort data from the KCMC zonal referral hospital Medical Birth Registry for 44,117 women who gave birth to singletons between 2000-2015. KCMC is located in the Moshi Municipality, Kilimanjaro region, northern Tanzania. Data analysis was performed using Stata version 15.1. Assuming a nonmonotone pattern of missingness, data were imputed using a fully conditional specification (FCS) technique under the missing at random (MAR) assumption. Multinomial regression models with robust standard errors were used to determine predictors of moderately to late ([32,37) weeks of gestation) and very/extreme (<32 weeks of gestation) preterm birth.

RESULTS

The overall proportion of preterm births among singleton births was 11.7%. The trends of preterm birth were significantly rising between the years 2000-2015 by 22.2% (95%CI 12.2%, 32.1%, p<0.001) for moderately to late preterm and 4.6% (95%CI 2.2%, 7.0%, p = 0.001) for very/extremely preterm birth category. After imputation of missing values, higher odds of moderately to late preterm delivery were among adolescent mothers (OR = 1.23, 95%CI 1.09, 1.39), with primary education level (OR = 1.28, 95%CI 1.18, 1.39), referred for delivery (OR = 1.19, 95%CI 1.09, 1.29), with pre-eclampsia/eclampsia (OR = 1.77, 95%CI 1.54, 2.02), inadequate (<4) antenatal care (ANC) visits (OR = 2.55, 95%CI 2.37, 2.74), PROM (OR = 1.80, 95%CI 1.50, 2.17), abruption placenta (OR = 2.05, 95%CI 1.32, 3.18), placenta previa (OR = 4.35, 95%CI 2.58, 7.33), delivery through CS (OR = 1.16, 95%CI 1.08, 1.25), delivered LBW baby (OR = 8.08, 95%CI 7.46, 8.76), experienced perinatal death (OR = 2.09, 95%CI 1.83, 2.40), and delivered male children (OR = 1.11, 95%CI 1.04, 1.20). Maternal age, education level, abruption placenta, and CS delivery showed no statistically significant association with very/extremely preterm birth. The effect of (<4) ANC visits, placenta previa, LBW, and perinatal death were more pronounced on the very/extremely preterm compared to the moderately to late preterm birth. Notably, extremely higher odds of very/extreme preterm birth were among the LBW babies (OR = 38.34, 95%CI 31.87, 46.11).

CONCLUSIONS

The trends of preterm birth have increased over time in northern Tanzania. Policy decisions should intensify efforts to improve maternal and child care throughout the course of pregnancy and childbirth towards preterm birth prevention. For a positive pregnancy outcome, interventions to increase uptake and quality of ANC services should also be strengthened in Tanzania at all levels of care, where several interventions can easily be delivered to pregnant women, especially those at high-risk of experiencing adverse pregnancy outcomes.

Do adults born preterm deliver preterm babies? A record linkage study from Western Australia

BACKGROUND

Infants born preterm at <37 + 0 weeks of gestation experience systemic complications later in adulthood. However, the risk of adults born preterm delivering preterm babies themselves is not well investigated.

METHODS

Midwives Notifications of births for the Western Australian population from 1980 to 2010 were obtained. A retrospective cohort study of 958,729 live-born singletons infants was conducted. Logistic regression was used to estimate odds ratios of preterm birth for preterm born parents compared to term born parents. Adjustment was made for socioeconomic status (quintiles of an area level disadvantage score), parity, maternal age, and ethnicity.

RESULTS

A total of 876,755 term and 81,974 preterm babies were born during the study period. Information on the preterm birth status of the mother or father was available for 138,123 children. Of these, 1555 (12.08%) children were born preterm to parents born preterm (either of the two parents were preterm), 11,504 (9.22%) preterm children were born to parents born at term, 11,319 term children were born to parents born preterm and 113,254 term children were born to parents born at term. 68,915 (8.39%) preterm children were born where parents' whose gestational age was unknown. The unadjusted and adjusted odds ratios with and 95% confidence intervals (CI) for the odds of preterm born adults delivering preterm child were 1.35 (1.29-1.42, p < .0001) and 1.25 (1.18-1.32, p < .0001) respectively. The adjusted odds ratio (with 95% CI) for Aboriginal vs Caucasian adults was 1.96 (1.91-2.01, p < .0001).

CONCLUSION

 In Western Australia delivering a preterm child is 25% greater when the parent was born preterm than when the parent was born at term in Western Australia. The effect appears to be transgenerational.

Acknowledging and Addressing Allostatic Load in Pregnancy Care

The USA is one of the few countries in the world in which maternal and infant morbidity and mortality continue to increase, with the greatest disparities observed among non-Hispanic Black women and their infants. Traditional explanations for disparate outcomes, such as personal health behaviors, socioeconomic status, health literacy, and access to healthcare, do not sufficiently explain why non-Hispanic Black women continue to die at three to four times the rate of White women during pregnancy, childbirth, or postpartum. One theory gaining prominence to explain the magnitude of this disparity is allostatic load or the cumulative physiological effects of stress over the life course. People of color disproportionally experience social, structural, and environmental stressors that are frequently the product of historic and present-day racism. In this essay, we present the growing body of evidence implicating the role of elevated allostatic load in adverse pregnancy outcomes among women of color. We argue that there is a moral imperative to assign additional resources to reduce the effects of elevated allostatic load before, during, and after pregnancy to improve the health of women and their children.

Developing a theoretical evolutionary framework to solve the mystery of parturition initiation

Eutherian mammals have characteristic lengths of gestation that are key for reproductive success, but relatively little is known about the processes that determine the timing of parturition, the process of birth, and how they are coordinated with fetal developmental programs. This issue remains one of biology's great unsolved mysteries and has significant clinical relevance because preterm birth is the leading cause of infant and under 5 year old child mortality worldwide. Here, we consider the evolutionary influences and potential signaling mechanisms that maintain or end pregnancy in eutherian mammals and use this knowledge to formulate general theoretical evolutionary models. These models can be tested through evolutionary species comparisons, studies of experimental manipulation of gestation period and birth timing, and human clinical studies. Understanding how gestation time and parturition are determined will shed light on this fundamental biological process and improve human health through the development of therapies to prevent preterm birth.

Estimating indirect parental genetic effects on offspring phenotypes using virtual parental genotypes derived from sibling and half sibling pairs

Indirect parental genetic effects may be defined as the influence of parental genotypes on offspring phenotypes over and above that which results from the transmission of genes from parents to their children. However, given the relative paucity of large-scale family-based cohorts around the world, it is difficult to demonstrate parental genetic effects on human traits, particularly at individual loci. In this manuscript, we illustrate how parental genetic effects on offspring phenotypes, including late onset conditions, can be estimated at individual loci in principle using large-scale genome-wide association study (GWAS) data, even in the absence of parental genotypes. Our strategy involves creating “virtual” mothers and fathers by estimating the genotypic dosages of parental genotypes using physically genotyped data from relative pairs. We then utilize the expected dosages of the parents, and the actual genotypes of the offspring relative pairs, to perform conditional genetic association analyses to obtain asymptotically unbiased estimates of maternal, paternal and offspring genetic effects. We apply our approach to 19066 sibling pairs from the UK Biobank and show that a polygenic score consisting of imputed parental educational attainment SNP dosages is strongly related to offspring educational attainment even after correcting for offspring genotype at the same loci. We develop a freely available web application that quantifies the power of our approach using closed form asymptotic solutions. We implement our methods in a user-friendly software package IMPISH (IMputing Parental genotypes In Siblings and Half Siblings) which allows users to quickly and efficiently impute parental genotypes across the genome in large genome-wide datasets, and then use these estimated dosages in downstream linear mixed model association analyses. We conclude that imputing parental genotypes from relative pairs may provide a useful adjunct to existing large-scale genetic studies of parents and their offspring.

Indirect parental genetic effects may be defined as the influence of parental genotypes on offspring phenotypes over and above that which results from the transmission of genes from parents to children. Estimating indirect parental genetic effects on offspring outcomes at the genotype level has been challenging because it requires large-scale, individual level genotypes from both parents and their offspring, and there is a paucity of cohorts around the world with this information. Here we present a new approach to estimate indirect parental genetic effects without the requirement of physically genotyped parents. Our method creates virtual parental genotypes based on the genotypes of offspring pairs, and then uses these virtual genotypes in downstream genetic association analyses. We developed a software package “IMPISH” that allows users to impute virtual parental genotypes in their own genome-wide datasets and then use these in downstream genome-wide association analyses, as well a series of power calculators to estimate the power to detect indirect parental genetic effects on offspring phenotypes. We apply our method to educational attainment data from the UK Biobank and show that indirect parental genetic effects are related to offspring educational attainment even after correcting for offspring genotype at the same loci.

Advancing human health in the decade ahead: pregnancy as a key window for discovery: A Burroughs Wellcome Fund Pregnancy Think Tank

Recent revolutionary advances at the intersection of medicine, omics, data sciences, computing, epidemiology, and related technologies inspire us to ponder their impact on health. Their potential impact is particularly germane to the biology of pregnancy and perinatal medicine, where limited improvement in health outcomes for women and children has remained a global challenge. We assembled a group of experts to establish a Pregnancy Think Tank to discuss a broad spectrum of major gestational disorders and adverse pregnancy outcomes that affect maternal-infant lifelong health and should serve as targets for leveraging the many recent advances. This report reflects avenues for future effects that hold great potential in 3 major areas: developmental genomics, including the application of methodologies designed to bridge genotypes, physiology, and diseases, addressing vexing questions in early human development; gestational physiology, from immune tolerance to growth and the timing of parturition; and personalized and population medicine, focusing on amalgamating health record data and deep phenotypes to create broad knowledge that can be integrated into healthcare systems and drive discovery to address pregnancy-related disease and promote general health. We propose a series of questions reflecting development, systems biology, diseases, clinical approaches and tools, and population health, and a call for scientific action. Clearly, transdisciplinary science must advance and accelerate to address adverse pregnancy outcomes. Disciplines not traditionally involved in the reproductive sciences, such as computer science, engineering, mathematics, and pharmacology, should be engaged at the study design phase to optimize the information gathered and to identify and further evaluate potentially actionable therapeutic targets. Information sources should include noninvasive personalized sensors and monitors, alongside instructive "liquid biopsies" for noninvasive pregnancy assessment. Future research should also address the diversity of human cohorts in terms of geography, racial and ethnic distributions, and social and health disparities. Modern technologies, for both data-gathering and data-analyzing, make this possible at a scale that was previously unachievable. Finally, the psychosocial and economic environment in which pregnancy takes place must be considered to promote the health and wellness of communities worldwide.

Dissecting maternal and fetal genetic effects underlying the associations between maternal phenotypes, birth outcomes, and adult phenotypes: A mendelian-randomization and haplotype-based genetic score analysis in 10,734 mother-infant pairs

BACKGROUND

Many maternal traits are associated with a neonate's gestational duration, birth weight, and birth length. These birth outcomes are subsequently associated with late-onset health conditions. The causal mechanisms and the relative contributions of maternal and fetal genetic effects behind these observed associations are unresolved.

METHODS AND FINDINGS

Based on 10,734 mother-infant duos of European ancestry from the UK, Northern Europe, Australia, and North America, we constructed haplotype genetic scores using single-nucleotide polymorphisms (SNPs) known to be associated with adult height, body mass index (BMI), blood pressure (BP), fasting plasma glucose (FPG), and type 2 diabetes (T2D). Using these scores as genetic instruments, we estimated the maternal and fetal genetic effects underlying the observed associations between maternal phenotypes and pregnancy outcomes. We also used infant-specific birth weight genetic scores as instrument and examined the effects of fetal growth on pregnancy outcomes, maternal BP, and glucose levels during pregnancy. The maternal nontransmitted haplotype score for height was significantly associated with gestational duration (p = 2.2 × 10-4). Both maternal and paternal transmitted height haplotype scores were highly significantly associated with birth weight and length (p < 1 × 10-17). The maternal transmitted BMI scores were associated with birth weight with a significant maternal effect (p = 1.6 × 10-4). Both maternal and paternal transmitted BP scores were negatively associated with birth weight with a significant fetal effect (p = 9.4 × 10-3), whereas BP alleles were significantly associated with gestational duration and preterm birth through maternal effects (p = 3.3 × 10-2 and p = 4.5 × 10-3, respectively). The nontransmitted haplotype score for FPG was strongly associated with birth weight (p = 4.7 × 10-6); however, the glucose-increasing alleles in the fetus were associated with reduced birth weight through a fetal effect (p = 2.2 × 10-3). The haplotype scores for T2D were associated with birth weight in a similar way but with a weaker maternal effect (p = 6.4 × 10-3) and a stronger fetal effect (p = 1.3 × 10-5). The paternal transmitted birth weight score was significantly associated with reduced gestational duration (p = 1.8 × 10-4) and increased maternal systolic BP during pregnancy (p = 2.2 × 10-2). The major limitations of the study include missing and heterogenous phenotype data in some data sets and different instrumental strength of genetic scores for different phenotypic traits.

CONCLUSIONS

We found that both maternal height and fetal growth are important factors in shaping the duration of gestation: genetically elevated maternal height is associated with longer gestational duration, whereas alleles that increase fetal growth are associated with shorter gestational duration. Fetal growth is influenced by both maternal and fetal effects and can reciprocally influence maternal phenotypes: taller maternal stature, higher maternal BMI, and higher maternal blood glucose are associated with larger birth size through maternal effects; in the fetus, the height- and metabolic-risk-increasing alleles are associated with increased and decreased birth size, respectively; alleles raising birth weight in the fetus are associated with shorter gestational duration and higher maternal BP. These maternal and fetal genetic effects may explain the observed associations between the studied maternal phenotypes and birth outcomes, as well as the life-course associations between these birth outcomes and adult phenotypes.

A Data-Driven Review of the Genetic Factors of Pregnancy Complications

Over the recent years, many advances have been made in the research of the genetic factors of pregnancy complications. In this work, we use publicly available data repositories, such as the National Human Genome Research Institute GWAS Catalog, HuGE Navigator, and the UK Biobank genetic and phenotypic dataset to gain insights into molecular pathways and individual genes behind a set of pregnancy-related traits, including the most studied ones—preeclampsia, gestational diabetes, preterm birth, and placental abruption. Using both HuGE and GWAS Catalog data, we confirm that immune system and, in particular, T-cell related pathways are one of the most important drivers of pregnancy-related traits. Pathway analysis of the data reveals that cell adhesion and matrisome-related genes are also commonly involved in pregnancy pathologies. We also find a large role of metabolic factors that affect not only gestational diabetes, but also the other traits. These shared metabolic genes include IGF2, PPARG, and NOS3. We further discover that the published genetic associations are poorly replicated in the independent UK Biobank cohort. Nevertheless, we find novel genome-wide associations with pregnancy-related traits for the FBLN7, STK32B, and ACTR3B genes, and replicate the effects of the KAZN and TLE1 genes, with the latter being the only gene identified across all data resources. Overall, our analysis highlights central molecular pathways for pregnancy-related traits, and suggests a need to use more accurate and sophisticated association analysis strategies to robustly identify genetic risk factors for pregnancy complications.

Mid-trimester amniotic fluid proteome's association with spontaneous preterm delivery and gestational duration

BACKGROUND

Amniotic fluid is clinically accessible via amniocentesis and its protein composition may correspond to birth timing. Early changes in the amniotic fluid proteome could therefore be associated with the subsequent development of spontaneous preterm delivery.

OBJECTIVE

The main objective of this study was to perform unbiased proteomics analysis of the association between mid-trimester amniotic fluid proteome and spontaneous preterm delivery and gestational duration, respectively. A secondary objective was to validate and replicate the findings by enzyme-linked immunosorbent assay using a second independent cohort.

METHODS

Women undergoing a mid-trimester genetic amniocentesis at Sahlgrenska University Hospital/Östra between September 2008 and September 2011 were enrolled in this study, designed in three analytical stages; 1) an unbiased proteomic discovery phase using LC-MS analysis of 22 women with subsequent spontaneous preterm delivery (cases) and 37 women who delivered at term (controls), 2) a validation phase of proteins of interest identified in stage 1, and 3) a replication phase of the proteins that passed validation using a second independent cohort consisting of 20 cases and 40 matched controls.

RESULTS

Nine proteins were nominally significantly associated with both spontaneous preterm delivery and gestational duration, after adjustment for gestational age at sampling, but none of the proteins were significant after correction for multiple testing. Several of these proteins have previously been described as being associated with spontaneous PTD etiology and six of them were thus validated using enzyme linked immunosorbent assay. Two of the proteins passed validation; Neutrophil gelatinase-associated lipocalin and plasminogen activator inhibitor 1, but the results could not be replicated in a second cohort.

CONCLUSIONS

Neutrophil gelatinase-associated lipocalin and Plasminogen activator inhibitor 1 are potential biomarkers of spontaneous preterm delivery and gestational duration but the findings could not be replicated. The negative findings are supported by the fact that none of the nine proteins from the exploratory phase were significant after correction for multiple testing.

Is the duration of human pregnancy decreasing? A vision of Darwinian medicine

Why do actual females have a 9-months-pregnancy? Here, we hypothesize that the pregnancies of prehuman species were longer than currently (10 or 11 months), and that anatomical and metabolic changes, by increasing the in-utero size of the fetal brain, selected groups with premature delivery, low-calcified and/or not welded cranial vault bones (permitting deformation during the expulsion), until reaching a current pregnancy duration of 9 months.

Proteomic analysis of Nrk gene-disrupted placental tissue cells explains physiological significance of NRK

Objective

NRK is a unique X chromosome-linked protein kinase expressed predominantly in placenta. The gene knockout causes placental overgrowth and delayed labor of Nrk-null fetuses from dams in mouse. To clarify unknown mechanisms behind the Nrk-null phenotypes, protein expression profiles were analyzed in the Nrk-null placenta using a high-performance two-dimensional electrophoresis methodology.

Results

Among around 1800 spots detected, we characterized a dozen protein spots whose expression levels were significantly altered in the Nrk-null placenta compared to wild-type. Analyzing these data sets is expected to reflect the difference physiologically in the presence or absence of NRK, facilitating the development of therapeutic strategies.

Spontaneous preterm labour that leads to preterm birth: An update and personal reflection

OBJECTIVE

The objective was to provide an update of progress made over time (including personal reflection) of our attempts to reduce the mortality and morbidity associated with spontaneous preterm labour that leads to preterm birth.

METHODS

An experienced and evidence based approach was taken to provide an overview of progress made over a generation (∼40 years) in our understanding of spontaneous preterm labour.

RESULTS

It is evident that we have made significant progress in our understanding of the aetiology, the measurement of the burden, the basic science, systems biology and mechanical pathways of the preterm parturition syndrome. We have better ways of predicting, preventing and managing spontaneous preterm labour than existed a generation ago.

CONCLUSIONS

The profile of spontaneous preterm labour that leads to preterm birth, thanks to organisations such as the March of Dimes, WHO and PREBIC is much more evident than before. However, while we have come a long way, we must not be complacent, and clinicians and basic scientists must continue to work in harmony, while recruiting and encouraging young investigators to join the effort to improve survival and handicap in what is one of the Great Obstetric Syndromes.