Preterm birth in evolutionary context: a predictive adaptive response?

Epigenetic signature of very low birth weight in young adult life

BACKGROUND

Globally, one in ten babies is born preterm (<37 weeks), and 1-2% preterm at very low birth weight (VLBW, <1500 g). As adults, they are at increased risk for a plethora of health conditions, e.g., cardiometabolic disease, which may partly be mediated by epigenetic regulation. We compared blood DNA methylation between young adults born at VLBW and controls.

METHODS

157 subjects born at VLBW and 161 controls born at term, from the Helsinki Study of Very Low Birth Weight Adults, were assessed for peripheral venous blood DNA methylation levels at mean age of 22 years. Significant CpG-sites (5'-C-phosphate-G-3') were meta-analyzed against continuous birth weight in four independent cohorts (pooled n = 2235) with cohort mean ages varying from 0 to 31 years.

RESULTS

In the discovery cohort, 66 CpG-sites were differentially methylated between VLBW adults and controls. Top hits were located in HIF3A, EBF4, and an intergenic region nearest to GLI2 (distance 57,533 bp). Five CpG-sites, all in proximity to GLI2, were hypermethylated in VLBW and associated with lower birth weight in the meta-analysis.

CONCLUSION

We identified differentially methylated CpG-sites suggesting an epigenetic signature of preterm birth at VLBW present in adult life.

IMPACT

Being born preterm at very low birth weight has major implications for later health and chronic disease risk factors. The mechanism linking preterm birth to later outcomes remains unknown. Our cohort study of 157 very low birth weight adults and 161 controls found 66 differentially methylated sites at mean age of 22 years. Our findings suggest an epigenetic mark of preterm birth present in adulthood, which opens up opportunities for mechanistic studies.

The pandemic preterm paradox: a test of competing explanations

Epidemiologists have long argued that side effects of the stress response include preterm birth. Research reports that fear of lethal infection stressed pregnant persons at the outset of the coronavirus disease (COVID-19) pandemic and that "shutdowns" and "social distancing" impeded access to social support and prenatal care. The decline in preterm births in high-income countries, including the United States, during the early months of the pandemic therefore poses a paradox for science. Explanations of this "pandemic preterm paradox" remain untested. We applied time-series modeling to data describing 80 monthly conception cohorts begun in the United States from July 2013 through February 2020 to determine which of 3 explanations most parsimoniously explained the paradox. We infer that "prior loss," or the argument that an increase in spontaneous abortions and stillbirths depleted the population of fetuses at risk of preterm birth, best explains data currently available. We describe the implications of these results for public health practice.

Breastfeeding Measurement - Teleological Considerations: Human Milk Collection for Research

We discuss the evolution and composition of breast milk and briefly describe how mammalian evolution resulted in lactation, which played a crucial role in infant growth and development. We focus on three teleological factors that significantly contribute to breast milk composition: (1) biological sex at birth, (2) gestational age, and (3) circadian rhythms. We also explain how these factors lead to variability in human milk composition. We emphasize the importance of standardizing the definitions of "preterm" and "term" to accurately study the effects of gestational age on milk composition. Finally, we discuss the role of the circadian clock in regulating lactation and the impact of breast milk on fetal and infant sleep. Investigators may integrate these critical factors when designing a research study that involves the collection of breast milk samples. Teleological factors greatly influence milk composition, and these factors may be considered when designing a study that requires breast milk. We provide both the rationale and application of solutions to address these factors.

Identifying Risk Factors for Premature Birth in the UK Millennium Cohort Using a Random Forest Decision-Tree Approach

Prior research on causes of preterm birth has tended to focus on pathophysiological processes while acknowledging the role of socioeconomic indicators. The present research explored a wide range of factors plausibly associated with preterm birth informed by pathophysiological and evolutionary life history perspectives on gestation length. To achieve this, a machine learning ensemble classification data analysis approach, random forest (RF), was applied to the UK Millennium Cohort (18,201 births). The results highlighted the importance of socioeconomic variables and parental age in predicting preterm (before 37 completed weeks) and very preterm (before 32 weeks) birth. Infants born in households with low income and with young fathers had an increased risk of both very preterm and preterm birth. Maternal health and health problems during pregnancy were not found to be useful predictors. The best-performing algorithm was for very preterm birth and had 93% sensitivity and 100% specificity using six variables. Algorithms predicting preterm birth before 37 weeks showed increased error, with out-of-bag error rates of about 7% versus only 1% for those predicting very preterm birth. The poorer performance of algorithms predicting preterm births to 37 weeks of gestation suggests that some preterm birth may not result from pathology related to poor maternal health or social or economic disadvantage, but instead represents normal life-history variation.

Difference between Preterm Birth in Adolescent and Adult Patients

Background: Preterm delivery represents an important public health problem due to its neonatal outcomes. There are numerous complications that occur due to prematurity, but the most significant one is represented by neonatal death. Even if the certain mechanism of prematurity is elusive, there are various risk factors known to be involved in the etiology of preterm birth, among which one is young age. Objectives: The present study aims to find whether preterm delivery has a higher rate in adolescent patients and if neonatal outcomes are different in adolescent and adult patients. Patients and methods:We performed an observational retrospective study about preterm infants from adolescent and adult patients. Thus, we analyzed 96 patients aged between 13 and 38 years who delivered in our unit between October 1st 2018 and December 31st 2021. Patients were divided into two groups: a study group (n=59), which included adolescents who delivered preterm, and a control group (n=37), which comprised adult patients who delivered preterm. We evaluated the rate of prematurity of all births and among patients enrolled in the present study and the neonatal outcome by newborn's weight, one-minute newborn's Apgar score and Neonatal Intensive Care Unit (NICU) admission. Results:In our study, the rate of prematurity was higher in adolescent patients, with a rate of 61.46%. The newborns' outcomes, analyzed by newborn's weight and one-minute Apgar score, were better in adolescent patients compared to adult ones. Therefore, newborns from adult patients needed neonatal intensive care more often, with a rate of 62.16%, while in the study group the percentage was 38.98%. The rate of antenatal care was higher in adult patients compared to adolescent ones (32.43% versus 27.12%). Conclusion:Adolescents have a higher risk of preterm delivery; however, their newborns have better outcomes than those of adult patients. The lack of antenatal care represents a risk factor for preterm delivery.

Hurricane Michael and Adverse Birth Outcomes in the Florida Panhandle: Analysis of Vital Statistics Data

OBJECTIVE

The aim of this study was to examine birth outcomes in areas affected by Hurricane Michael.

METHODS

Vital statistics data of 2017-2019 were obtained from the state of Florida. Births occurring in the year before and after the date of Hurricane Michael (October 7, 2018) were used. Florida counties were divided into 3 categories reflecting extent of impact from Hurricane Michael. Birth outcomes including incidence of preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) were also compared before and after Hurricane Michael. Spontaneous and indicated PTBs were distinguished based on previously published algorithms. Multiple regression was used to control for potential confounders.

RESULTS

Both LBW (aRR 1.19, 95% CI: 1.07, 1.32) and SGA (aRR 1.11, 95% CI: 1.01, 1.21) were higher in the year after Michael than the year before in the most-affected area; a similar effect was not seen in other areas. A stronger effect was seen for exposure in the first trimester or in the 2 months after Michael than in the second or third trimester.

CONCLUSION

Consistent with many previous studies, this study of Hurricane Michael found an effect on fetal growth.

Prevalence of Preterm Birth Rate During COVID-19 Lockdown in a Tertiary Care Hospital, Riyadh

Background On March 3, 2020, the first case of coronavirus disease (COVID-19) was reported by the Ministry of Health, Kingdom of Saudi Arabia. Within days, the government confirmed more cases and adopted lockdown measures with travel restrictions from March to June 2020. A distinctive coronavirus was isolated from 190,823 patients by June 30. The pandemic resulted in a significant risk to public health. The study aimed to evaluate the impact of COVID-19 lockdown on the rate of premature births. Method In this cross-sectional study, we observed premature births at the Neonatal Intensive Care Unit (NICU). The study site is a 1,500-bed teaching hospital, with around 4,500 annual deliveries, 70 beds in level II and level III, and tertiary care NICU. We compared the birth rates among preterm infants between March 1 to June 30, 2017-2019, to the similar calendar months of 2020. Information on nationality, gestational age, and maternal conditions were collected from the medical records. We used the Poisson regression model to assess the preterm birth rate's temporal trends before lockdown versus during lockdown. Results Among 7,226 total live neonates, we recorded 1,320 preterm infants during the study period of 2017-2020. The preterm birth rate per 1,000 live births during lockdown showed a 23% drop in the overall preterm birth rate with Prevented Fraction of 36% in extremely preterm (<28 weeks gestational age) births and 26% in moderate/late premature (32 weeks to 36 weeks + 6 days gestational age) births. The estimated preterm birth rate among the Saudi expats (15.11/1,000 live births) showed an increased tendency compared to Saudi nationals (odds ratio [OR]=1.07; 95% CI: 0.75-1.52) and was statistically not significant during the strict lockdown. Conclusion There was a significant reduction in the birth rate of extremely preterm and moderate/late preterm infants during lockdown when compared to the preceding three years. A national dataset is required to evaluate the extent of lockdown's impact on the preterm birth rate.

Stress and Metabolomics for Prediction of Spontaneous Preterm Birth: A Prospective Nested Case-Control Study in a Tertiary Hospital

Spontaneous preterm birth (sPTB) is the leading cause of infant morbidity and mortality worldwide. Deficiency of effective predict methods is an urgent problem that needs to be solved. Numbers of researchers spare no efforts to investigate differential indicators. To evaluate the value of the differential indicators, a prospective nested case-control study was carried out. Among an overall cohort of 1,050 pregnancies, 20 sPTB pregnancies, and 20 full-term pregnancies were enrolled in this study. Participants were followed-up until labor. The psychological profile was evaluated utilizing the Zung Self-Rating Depression Scale at 11-14 weeks. Stress-related biomarker-cortisol and metabolites were detected by Electrochemiluminescence Immunoassay (ECLIA) and Gas Chromatography-Mass Spectrometry (GC-MS) in serum samples during pregnancy, respectively. The expression level of cortisol was up-regulated in serum and the score of the Zung Self-Rating Depression Scale was significantly higher in the sPTB group when compared to the control group. Note that, 29 metabolomics were differentially expressed between the sPTB group and the control group. The scores of the Zung Self-Rating Depression Scale, the level of cortisol, Eicosane, methyltetradecanoate, and stearic acid in serum were selected to establish the model with lasso logistic regression. Validation of the model yielded an optimum corrected AUC value of 89.5%, 95% CI: 0.8006-0.9889 with a sensitivity of 100.0%, and specificity of 78.9%. In conclusion, this study establishes a prediction model of sPTB with five variables, which may predict sPTB more accurately and sensitively in the second trimester.

The Association Between Coffee and Tea Consumption During Pregnancy and Preterm Delivery: Case-Control Study

Objective

To assess a possible association between coffee and tea consumption and preterm delivery.

Methods

A case-control design was implemented on a sample of women who were admitted for delivery to a tertiary hospital in the north of Jordan. Three hundred and fourteen cases and 796 controls were evaluated. The study was conducted while women were in the hospital for delivery. They were questioned about coffee and tea consumption and relevant confounding factors. Women were asked to state the average number of coffee and tea cups they drank per day.

Results

The mean coffee consumption among women with preterm delivery was 0.75 cups/day ±1.23 and the mean tea consumption was 1.47 cups/day± 1.76. Multivariable logistic analysis revealed that increased age (OR=1.05; CI=1.02-1.08), parity (OR=3.82, CI=2.58-5.64), history of abortions (OR=1.69; CI=1.21-2.35), family history of preterm deliveries (OR=2.45, CI=1.33-4.52), having treatment for subfertility (OR=12.14, CI=2.39-61.62), diabetes mellitus (OR=2.22, CI=1.06-4.66), worsened emotional status during pregnancy (OR=2.35, CI=1.49-3.72), short inter-pregnancy interval (OR=1.72, CI=1.10-2.72), no iron consumption (OR=1.46, CI=1.06-2.03), using folic acid (OR=2.45, CI=1.33-4.52), and black colour women (OR=2.87, CI=1.35-6.10) were predictive for preterm delivery. After controlling for all significant predictors, coffee and tea consumption during pregnancy was not significantly associated with increased odds of preterm delivery.

Conclusion

These results do not support an association between coffee and tea consumption and preterm delivery.

Maternal exposure to Wenchuan earthquake and prolonged risk of offspring birth outcomes: a natural experiment study

Background

The prolonged effects of disasters on reproductive outcomes among the survivors are less studied, and the findings are inconsistent. We examined the associations of maternal exposure to the 2008 Wenchuan earthquake years before conception with adverse birth outcomes.

Methods

We included 73,493 women who delivered in 96 hospitals in 24 provinces and autonomous regions from the 2015/16 China Labor and Delivery Survey. We weighted the multivariable logistic models based on the combination of coarsened exact matching (CEM) weight and survey weight, and performed sex-stratified analysis to test whether associations of maternal earthquake exposure with adverse birth outcomes (Stillbirth, preterm birth [PTB], low birthweight [LBW], and small for gestational age [SGA]) varied by sex.

Results

The bivariate models showed that the weighted incidence of each adverse birth outcome was higher in exposed group than unexposed group: stillbirth (2.00% vs. 1.33%), PTB (14.14% vs. 7.32%), LBW (10.82% vs. 5.76%), and SGA (11.32% vs. 9.52%). The multivariable models showed maternal earthquake exposure was only associated significantly with a higher risk of PTB in offspring among all births (adjusted risk ratio [aRR](95%CI):1.25(1.06–1.48), P = 0.010). The sex-stratified analysis showed the association was significant among male births (aRR (95%CI): 1.40(1.12–1.75),P = 0.002),but unsignificant among female births. The sensitivity analysis reported similar findings.

Conclusions

The 2008 Wenchuan earthquake exposure has a long-term effect on PTB. Maternal acute exposure to disasters could be a major monitor for long-term reproductive outcomes. More attention should be paid to the underlining reasons for disaster-related adverse birth outcomes.

The pregnant myometrium is epigenetically activated at contractility-driving gene loci prior to the onset of labor in mice

During gestation, uterine smooth muscle cells transition from a state of quiescence to one of contractility, but the molecular mechanisms underlying this transition at a genomic level are not well-known. To better understand these events, we evaluated the epigenetic landscape of the mouse myometrium during the pregnant, laboring, and postpartum stages. We generated gestational time point–specific enrichment profiles for histone H3 acetylation on lysine residue 27 (H3K27ac), histone H3 trimethylation of lysine residue 4 (H3K4me3), and RNA polymerase II (RNAPII) occupancy by chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq), as well as gene expression profiles by total RNA-sequencing (RNA-seq). Our findings reveal that 533 genes, including known contractility-driving genes (Gap junction alpha 1 [Gja1], FBJ osteosarcoma oncogene [Fos], Fos-like antigen 2 [Fosl2], Oxytocin receptor [Oxtr], and Prostaglandin G/H synthase 2 (Ptgs2), for example), are up-regulated at day 19 during active labor because of an increase in transcription at gene bodies. Labor-associated promoters and putative intergenic enhancers, however, are epigenetically activated as early as day 15, by which point the majority of genome-wide H3K27ac or H3K4me3 peaks present in term laboring tissue is already established. Despite this early exhibited histone signature, increased noncoding enhancer RNA (eRNA) production at putative intergenic enhancers and recruitment of RNAPII to the gene bodies of labor-associated loci were detected only during labor. Our findings indicate that epigenetic activation of the myometrial genome precedes active labor by at least 4 days in the mouse model, suggesting that the myometrium is poised for rapid activation of contraction-associated genes in order to exit the state of quiescence.

A study of the epigenomic and transcriptomic basis of pregnancy and labor onset in a mouse model identifies genes that are epigenetically poised for activation four days before labour onset, and implicates AP-1 transcription factors in the up-regulation of genes during labor.

Dysregulation of bile acids increases the risk for preterm birth in pregnant women

Preterm birth (PTB) is the leading cause of perinatal mortality and newborn complications. Bile acids are recognized as signaling molecules regulating a myriad of cellular and metabolic activities but have not been etiologically linked to PTB. In this study, a hospital-based cohort study with 36,755 pregnant women is conducted. We find that serum total bile acid levels directly correlate with the PTB rates regardless of the characteristics of the subjects and etiologies of liver disorders. Consistent with the findings from pregnant women, PTB is successfully reproduced in mice with liver injuries and dysregulated bile acids. More importantly, bile acids dose-dependently induce PTB with minimal hepatotoxicity. Furthermore, restoring bile acid homeostasis by farnesoid X receptor activation markedly reduces PTB and dramatically improves newborn survival rates. The findings thus establish an etiologic link between bile acids and PTB, and open an avenue for developing etiology-based therapies to prevent or delay PTB.

Plasma Adipokines Profile in Prepubertal Children with a History of Prematurity or Extrauterine Growth Restriction

Adipose tissue programming could be developed in very preterm infants with extrauterine growth restriction (EUGR), with an adverse impact on long-term metabolic status, as was studied in intrauterine growth restriction patterns. The aim of this cohort study was to evaluate the difference in levels of plasma adipokines in children with a history of EUGR. A total of 211 school age prepubertal children were examined: 38 with a history of prematurity and EUGR (EUGR), 50 with a history of prematurity with adequate growth (PREM), and 123 healthy children born at term. Anthropometric parameters, blood pressure, metabolic markers and adipokines (adiponectin, resistin, leptin) were measured. Children with a history of EUGR showed lower values of adiponectin (μg/mL) compared with the other two groups: (EUGR: 10.6 vs. PREM: 17.7, p < 0.001; vs. CONTROL: 25.7, p = 0.004) and higher levels of resistin (ng/mL) (EUGR: 19.2 vs. PREM: 16.3, p =0.007; vs. CONTROL: 7.1, p < 0.001. The PREM group showed the highest values of leptin (ng/mL), compared with the others: PREM: 4.9 vs. EUGR: 2.1, p = 0.048; vs. CONTROL: 3.2, p = 0.029). In conclusion, EUGR in premature children could lead to a distinctive adipokines profile, likely associated with an early programming of the adipose tissue, and likely to increase the risk of adverse health outcomes later in life.

Developing differences: early-life effects and evolutionary medicine

Variation in early-life conditions can trigger developmental switches that lead to predictable individual differences in adult behaviour and physiology. Despite evidence for such early-life effects being widespread both in humans and throughout the animal kingdom, the evolutionary causes and consequences of this developmental plasticity remain unclear. The current issue aims to bring together studies of early-life effects from the fields of both evolutionary ecology and biomedicine to synthesise and advance current knowledge of how information is used during development, the mechanisms involved, and how early-life effects evolved. We hope this will stimulate further research into early-life effects, improving our understanding of why individuals differ and how this might influence their susceptibility to disease. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.

Adiponectin links maternal metabolism to uterine contractility

Adiponectin is secreted by adipose tissue and promotes insulin sensitivity. Low circulating adiponectin is associated with increased risk for preterm labor, but the influence of adiponectin on uterine myometrial physiology is unknown. We hypothesized that adiponectin receptors (AdipoRs) decrease myometrial contractility via AMPK to promote uterine quiescence in pregnancy. Using quantitative RT-PCR, we found that nonpregnant or pregnant human and mouse myometrium express AdipoR1 and AdipoR2 mRNAs. We confirmed AdipoR2 protein expression in human and mouse myometrium, with increased abundance in late mouse pregnancy. Both recombinant adiponectin and a pharmacologic AdipoR agonist, AdipoRon, potently inhibited uterine myometrial strip contractions in physiologic organ bath. The relaxation was independent of contractile stimulus (oxytocin, KCl, U46619). AdipoR agonists increased AMPK phosphorylation in pregnant mouse myometrium, and the direct AMPK activator A769662 also relaxed myometrial strips. However, the AMPK inhibitor dorsomorphin (compound C) blocked AMPK phosphorylation but did not abolish relaxation with either AdipoRon or A769662. In summary, adiponectin inhibits myometrial contractility consistent with the possibility that it is a previously unrecognized link between maternal metabolism and pregnancy maintenance. We also identify a separate role for AMPK regulating myometrial contractions that may influence labor onset.-Vyas, V., Guerra, D. D., Bok, R., Powell, T., Jansson, T., Hurt, K. J. Adiponectin links maternal metabolism to uterine contractility.

The role of complement in preterm birth and prematurity

Complications of preterm birth (PTB) are the global leading cause of death in children younger than 5 years of age. Almost 15 million children are born prematurely in the world each year. Increasing evidence suggests that labor and delivery have many hallmarks of an inflammatory reaction, where complement activation has an active participation. As one of the most important components of inflammation, the role of complement during labor and PTB is becoming an attractive research target. The complement components C1q and C5b-9 are deposited on fetal membranes and release inflammatory mediators that contribute to uterine contractions, cervical ripening, cell chemotaxis, metalloproteinases production, membrane awaking and rupture, and it participates as a co-adjuvant in the onset and progress of labor. This article reviews a basic description of the complement system, its role in preterm birth and current concepts regarding its contribution in novel therapy strategies and new biomarkers.