The Role of Genetics in Preterm Birth

Environmental and genetic risk factors for preterm birth: interplays with stressful events during pregnancy

BACKGROUND

Preterm birth (PTB) etiology remains poorly understood. Our aim was to investigate the relation of environmental factors and specific gene polymorphisms involved in PTB in the context of stressful life events during pregnancy.

METHODS

Parental sociodemographic and obstetric data as well as genetic variants of 1263 preterm newborns were analyzed. Logistic regressions were used to identify shared environmental and genetic risk factors for PTB and stressful life events. A Lasso Ridge logistic regression with cross-validation was used to select the best predictors of maternal stress. Associations were evidenced through Bayesian networks.

RESULTS

Starting from a great number of variables, our model was processed and reduced until it allowed to visualize only two environmental factors (alcohol intake and chronic hypertension) along with three SNPs rs66911171 (CR1), rs854552 (PON1), rs4966038 (IGF1R) and two interactions rs854552 x rs4966038 (PON1xIGFR1) and rs5742612 x rs1942386 (IGF1xPGR) related to PTB and maternal stress.

CONCLUSION

Machine learning techniques allow us to identify two environmental factors, three genetic markers, and two interactions related to PTB in the context of stressful life events. Findings of this exploratory study contribute to the understanding of the complex pathways relating maternal stress and PTB.

IMPACT

An analysis of environmental factors and preterm birth specific gene polymorphisms in the context of stressful life events during pregnancy is presented. Alcohol intake and chronic hypertension along with SNPs of CR1, PON1, IGF1R and two interactions PON1xIGFR1 and IGF1xPGR are shown as related to preterm birth in the context of stressful life events. This research could help in developing targeted interventions and preventive strategies for at-risk populations. The study emphasizes the potential of machine learning to interpret biological and social interactions affecting health outcomes.

Experiences of multiple psychosocial stressors and associations with oxidative stress biomarkers during pregnancy

BACKGROUND

Oxidative stress is hypothesized to be one mechanism linking psychosocial stressor exposure to preterm birth and other adverse pregnancy outcomes. However, prior studies have focused solely on singular psychosocial stressors, which may not reflect real world exposures as pregnant women may experience multiple stressors simultaneously.

METHODS

Participants included a subset of the Chemicals in Our Bodies cohort, a prospective birth cohort in San Francisco, California (N = 227). Self -reported psychosocial stressors were assessed via questionnaires administered during the second trimester that addressed financial strain, food insecurity, job strain, neighborhood quality, caregiving, stressful life events, unplanned pregnancy, and perceived community status. Oxidative stress biomarkers were measured during the second trimester of pregnancy and included 15-F2t-IsoP, and its two major metabolites 2,3-dinor-5,6-dihydro-15-F2t-IsoP, and 2,3-dinor-15-F2t-IsoP, and PGF2α. Linear regression models were used to examine associations between individual and pairwise combinations of psychosocial stressors in relation to each oxidative stress biomarker.

RESULTS

15-F2t-IsoP, 2,3-dinor-15-F2t-IsoP, and 2,3-dinor-5,6-dihydro-15-F2t-IsoP were elevated among participants reporting experiences of low perceived community status, job strain, poor neighborhood quality, food insecurity, and stressful life events (e.g., β = 0.36, 95 % CI = 0.00, 0.72 for food insecurity in association with 15-F2t-IsoP). In models that included pairwise combinations of stressor exposures, nearly every combination was also associated with an increase in all oxidative stress biomarkers compared to those who experienced one or neither stressor. For example, stressful life events and poor neighborhood quality was associated with statistically significant increases in all biomarkers (e.g., β = 0.94, 95 % CI = 0.17, 1.71 for 2,3-dinor-5,6-dihydro-15-F2t-IsoP).

CONCLUSIONS

Urinary oxidative stress biomarkers were elevated among pregnant women exposed to psychosocial stressors, and exposure to multiple stressors resulted in the strongest associations. These findings support oxidative stress as one potential biological pathway linking prenatal psychosocial stress to preterm birth and other adverse pregnancy outcomes.

Association of maternal prenatal phthalate exposure and genetic polymorphisms of metabolic enzyme genes with spontaneous preterm birth: a nested case-control study in China

BACKGROUND

The relationship between prenatal phthalate exposure and preterm birth from previous studies has been inconsistent. Meanwhile, few studies have explored the relationship between spontaneous preterm birth (SPTB) and genetic polymorphisms of metabolic enzyme genes or gene-phthalate interactions. The aim of this study is to evaluate the association of maternal phthalate exposure, genetic polymorphisms, and their interactions with SPTB.

METHODS

A total of 182 cases with SPTB and 321 controls with full-term delivery were enrolled. Nine phthalate metabolites in maternal second trimester urine samples were measured by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. Genotyping was performed on twenty-six single nucleotide polymorphisms (SNPs) of metabolic enzyme genes, including CYP2C9, CYP2C19, UGT1A7, UGT2B7 and UGT2B15 genes. The associations between maternal phthalate exposure or genetic polymorphisms and SPTB were estimated by multivariable logistic regression analysis. The impact of interactions between gene-gene and gene-phthalate exposure on SPTB were analyzed via generalized multifactor dimensionality reduction.

RESULTS

There were no significant differences in the concentrations of phthalate metabolites between the two groups. No statistically significant associations were observed between maternal phthalate exposure and SPTB. The rs4244285 polymorphism of CYP2C19 gene was associated with decreased odds of SPTB under the log-additive (aOR = 0.73, 95% CI: 0.55-0.98) and recessive model (aOR = 0.37, 95% CI: 0.18-0.74). Two SNP loci of UGT2B15 were associated with increased odds of SPTB under the recessive genetic model (aOR = 3.85, 95% CI: 1.31-11.35 for rs3100, and aOR = 3.85, 95% CI: 1.31-11.35 for rs4148269). However, these associations were not significant after the false discovery rate correction. No significant gene-gene or gene-phthalate metabolites interactions for SPTB were observed.

CONCLUSIONS

Maternal phthalate exposure in the present subjects and genetic polymorphisms of metabolic enzyme genes were not associated with SPTB. Moreover, there were no significant gene-gene or gene-phthalates interactions for SPTB.

The single-cell immune profile throughout gestation and its potential value for identifying women at risk for spontaneous preterm birth

Precisely timed immune adaptations, observed in the maternal circulation, underpin the notion of an immune clock of human pregnancy that supports its successful progression and completion at delivery. This immune clock is divided into three immunological phases, with the first phase starting at the time of conception and implantation, shifting into the second phase that supports homeostasis and tolerance throughout pregnancy, and culminating in the last phase of labor and parturition. Disruptions of this immune clock are reported in pregnancy complications such as spontaneous preterm birth. However, our understanding of the immune clock preceding spontaneous preterm birth remains scattered. In this review, we describe the chronology of maternal immune cell adaptations during healthy pregnancies and highlight its disruption in spontaneous preterm birth. With a focus on single-cell cytometric, proteomic and transcriptomic approaches, we review recent studies of term and spontaneous preterm pregnancies and discuss the need for future prospective studies aimed at tracking pregnancies longitudinally on a multi-omic scale. Such studies will be critical in determining whether spontaneous preterm pregnancies progress at an accelerated pace or follow a preterm-intrinsic pattern when compared to those delivered at term.

MTHFR Gene Polymorphisms and DNA Methylation in Idiopathic Spontaneous Preterm Birth

Background and Objectives: Preterm birth (PTB) is a complex condition with various contributing factors, including genetic and epigenetic influences such as DNA methylation. Methylenetetrahydrofolate reductase (MTHFR) plays a critical role in DNA methylation and the remethylation of homocysteine. This study aimed to investigate the association between maternal MTHFR C677T and A1298C polymorphisms, LINE-1 DNA methylation levels, and the risk of idiopathic spontaneous preterm birth (SPTB) in Caucasian women from Croatia and Slovenia. Materials and Methods: A total of 50 women with SPTB (<34 weeks of gestation) and 50 control women were included in the study. MTHFR polymorphisms were analyzed using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), and LINE-1 DNA methylation levels were quantified using the MethyLight method. Results: The study found no significant differences in MTHFR C677T and A1298C polymorphisms' genotype or allele frequencies between women with SPTB and controls. Additionally, no statistical significance of LINE-1 DNA methylation was found between the genotypes of the MTHFR polymorphisms analyzed. Conclusions: The study suggests no conclusive association between MTHFR C677T and A1298C polymorphisms, LINE-1 DNA methylation, and SPTB in Croatian and Slovenian women. Considering prior evidence connecting MTHFR polymorphisms, hyperhomocysteinemia, and PTB, the lack of homocysteine measurements and unassessed impact of folate or vitamin B supplementation limit the conclusions.

Effectiveness of calcium supplementation in the prevention of gestational hypertension: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Gestational hypertension and related disorders, such as preeclampsia, pose significant risks to maternal and foetal health. Calcium supplementation has been proposed as a preventive measure, but its effectiveness remains debated. This review assess the impact of calcium supplementation in prevention of gestational hypertension.

METHODS

A comprehensive literature search was conducted across multiple databases, including Scopus, EMBASE, PubMed, Web of Science, CINAHL, Cochrane CENTRAL, from inception to July 2024. Eligibility criteria included studies involving pregnant women at risk of gestational hypertension, comparing calcium supplementation to control group, and reporting on outcomes such as preeclampsia, pregnancy-induced hypertension, HELLP syndrome, preterm birth, and maternal mortality. Data were analysed using a random-effects inverse-variance model to calculate pooled risk ratios (RRs) and assess heterogeneity using Cochran's Q and I2 statistics. Publication bias was evaluated using funnel plots and Egger's test.

RESULTS

22 studies with 39,270 individuals were included. Most studies had higher risk of bias. Calcium supplementation significantly reduced the risk of preeclampsia (pooled RR = 0.606, 95 %CI: 0.483-0.761, p < 0.001) and pregnancy-induced hypertension (pooled RR = 0.870, 95 %CI: 0.759-0.996, p = 0.044). However, it showed no significant effect on HELLP syndrome, preterm birth, or mortality. Heterogeneity was moderate to substantial across outcomes, and publication bias was detected for preterm birth and pregnancy-induced hypertension.

CONCLUSION

Calcium supplementation during pregnancy significantly reduces the risk of preeclampsia and pregnancy-induced hypertension, highlighting its value as a cost-effective intervention for improving maternal health. These findings support integrating calcium supplementation into prenatal care strategies, particularly for populations with low dietary calcium intake.

Extrauterine support of pre-term lambs achieves similar transcriptomic profiling to late pre-term lamb brains

Our group has developed an extra-uterine environment for newborn development (EXTEND) using an ovine model, that aims to mimic the womb to improve short and long-term health outcomes associated with prematurity. This study's objective was to determine the histologic and transcriptomic consequences of EXTEND on the brain. Histology and RNA-sequencing was conducted on brain tissue from three cohorts of lambs: control pre-term (106-107 days), control late pre-term (127 days), and EXTEND lambs who were born pre-term and supported on EXTEND until late pre-term age (125-128 days). Bioinformatic analysis determined differential gene expression among the three cohorts and across four different brain tissue sections: basal ganglia, cerebellum, hippocampus, and motor cortex. There were no clinically relevant histological differences between the control late pre-term and EXTEND ovine brain tissues. RNA-sequencing demonstrated that there was greater differential gene expression between the control pre-term lambs and EXTEND lambs than between the control late pre-term lambs and EXTEND lambs (Supplemental Figs. 1 and 2). Our study demonstrates that the use of EXTEND to support pre-term lambs until they reach late pre-term gestational age results in brain tissue gene expression that more closely resembles that of the lambs who reached late pre-term gestation within their maternal sheep's womb than that of the lambs who were born prematurely.

Cerebral palsy as a childhood-onset neurological disorder caused by both genetic and environmental factors

Cerebral palsy (CP) is a clinical term used to describe a spectrum of movement and posture disorders resulting from non-progressive disturbances in the developing fetal brain. The clinical diagnosis of CP does not include pathological or aetiological defining features, therefore both genetic and environmental causal pathways are encompassed under the CP diagnostic umbrella. In this review, we explore several genetic causal pathways, including both monogenic and polygenic risks, and present evidence supporting the multifactorial contributions to CP. Historically, CP has been associated with various risk factors such as pre-term birth, multiple gestation, intrauterine growth restriction (IUGR), maternal infection, and perinatal asphyxia. Thus, we also examine genetic predispositions that may contribute to these risk factors. Understanding the specific aetiology of CP enables more tailored treatments, especially with the increasing potential for early genetic testing.

Precision medicine activities and opportunities for shaping maternal and neonatal health in Qatar

Precision Medicine (PM) is a transformative clinical medicine strategy that aims to revolutionize healthcare by leveraging biological information and biomarkers. In the context of maternal and neonatal health, PM enables personalized care from preconception through the postnatal period. Qatar has emerged as a key player in PM research, with dedicated programs driving advancements and translating cutting-edge research into clinical applications. This article delves into neonatal and maternal health in Qatar, emphasizing PM programs and initiatives that have been implemented. It also features noteworthy clinical cases that demonstrate the effectiveness of precision interventions. Furthermore, the article highlights the role of pharmacogenomics in addressing various maternal health conditions. The review further explores potential advancements in the application of PM in maternal and neonatal healthcare in Qatar.

Preterm birth, low birth weight, and their co-occurrence among women with preexisting chronic diseases prior to conception: a cross-sectional analysis of postpartum women in a low-resource setting in Ghana

BACKGROUND

The incidence of chronic diseases, which are significant contributors to maternal deaths and adverse new-born outcomes, is increasing among women of reproductive age in northern Ghana. This emerging health issue raises serious concerns about the potential exacerbation of adverse birth outcomes in this setting, given that it is one of the regions in the country with a high incidence of such outcomes. We investigated the risks of preterm birth (PTB), low birth weight (LBW), and concurrent PTB and LBW among women with preexisting chronic conditions prior to conception in the Tamale Metropolis of northern Ghana.

METHODS

A facility-based cross-sectional study was conducted among 420 postpartum women randomly selected from five public health facilities. Information was collected electronically on participants' self-reported experience of chronic conditions, namely, hypertension, diabetes, asthma, heart disease, and sickle cell disease, prior to their most recent pregnancy. Information on gestational age at delivery and birth weight was also collected. Regression modeling was used to quantify the risk of adverse newborn outcomes among women who reported preexisting chronic conditions prior to pregnancy.

RESULTS

Chronic diseases affected 31.2% of our sample. Of these, 28.6% had a single chronic condition, while 2.6% had comorbid chronic conditions. The prevalence of PTB was 24.0% (95% CI: 20.2, 28.4), 27.6% (95% CI: 23.5, 32.1) of the newborns were born LBW, and 17.4% (95% CI: 14.0, 21.3) of the pregnancies resulted in both PTB and LBW. Compared with those without chronic conditions, women with chronic conditions prior to conception had a greater risk of PTB (aOR = 6.78, 95% CI: 3.36, 13.68), LBW (aOR = 5.75, 95% CI: 2.96, 11.18), and the co-occurrence of PTB and LBW (aOR = 7.55, 95% CI: 3.32, 17.18).

CONCLUSIONS

We observed significant rates of PTB, LBW, and the co-occurrence of PTB and LBW among women who were already aware that they had preexisting chronic conditions prior to conception. Our findings highlight a potential gap in the quality of prenatal care provided to these women before delivery. Preconception care may offer an opportunity to address preexisting chronic conditions in women before pregnancy and potentially improve maternal and newborn health outcomes.

Ethics of Predicting and Preventing Preterm Birth

Preterm birth (PTB) occurs disproportionately among women who are minoritized and who live and work in poverty. This disadvantage occurs as a result of societal norms and policies that affect how people are treated and determine their access to a broad range of resources. Research that takes social context into account offers the best opportunity for identifying approaches to prevent PTB. The experience and knowledge of women from groups experiencing high rates of PTB can provide important insights for research design and for determining the feasibility and acceptability of potential interventions.

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.

Leptin and Leptin Receptor Polymorphisms in Infants and Their Parents: Correlation with Preterm Birth

It has been proven that single-nucleotide polymorphisms (SNPs) in LEP and LEPR genes could predispose individuals to an increased risk of pregnancy adverse outcomes (PAOs) such as recurrent pregnancy loss (RPL) and pre-eclampsia. Preterm birth (PTB) is the leading cause of infant mortality. We decided to investigate the correlation between PTB and LEP and LEPR SNPs. The study cohort included families who underwent spontaneous PTB and control samples of families who had at-term-born (≥37 weeks of gestational age) children. Swabs were performed by rubbing the sticky end for about 30 s on the gum and on the inside of the cheek, allowing us to collect the flaking cells of the oral mucosa. Genotyping of the three SNPs-LEPRA668G, LEPG2548A and A19G-was carried out via an ARMS-MAMA real-time PCR procedure, as previously described. Regarding LEPG2548A, we found that the most expressed genotype in infants both in the preterm and the at-term group was AG; however, we did not discover any statistically significant difference (p = 0.97). Considering LEPA19G, none among the infants and parents were found to carry the AA genotype. No statistically significant differences were found between children, mothers and fathers belonging to preterm and at-term groups. We did not find a statistically significant association in newborns and their mother, but our results show a statistical correlation with the LEPRA668G genotype GG of the father. This fact can contribute to defining genetic risk factors for PTB. Further studies are certainly needed to better clarify the role of genetics in influencing preterm delivery.

Genetic association study of preterm birth and gestational age in a population-based case-control study in Peru

BACKGROUND

Preterm birth (PTB) affects ∼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.

METHODS

PTB cases delivered≥20 weeks' but < 37 weeks' gestation, while controls delivered at term (≥37 weeks but <42 weeks). Multivariable regressions were used to identify genetic markers for PTB and GA (∼6 million SNPs), adjusting for maternal age and the first two genetic principal components. In silico functional analysis was conducted among top signals detected with an arbitrary P < 1.0×10-5 . We sought to replicate genetic markers for PTB and GA identified in Europeans, and we developed a genetic risk score for GA based on European markers.

RESULTS

Mean GA was 30 ± 4 weeks in PTB cases (N = 933) and 39 ± 1 in the controls (N = 1,279). No associatiosn were identified at genome-wide level. Nominal PTB variants were enriched for biological pathways associated with polyketide, progesterone, steroid hormones, and glycosyl metabolism. Nominal GA variants were enriched in intronic regions and cancer pathways. Variants in WNT4 associated with GA in Europeans were replicated in our study. A genetic risk score was associated with a 2-day longer GA (P = 0.002) in our sample.

CONCLUSIONS

This study identified various signals suggestively associated with PTB and GA in pregnant Peruvian women. None of these variants overlapped with signals previously identified in Europeans.

Genetic association study of Preterm birth and Gestational age in a population-based case-control study in Peru: Genetics of PTB and GA in pregnant women 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 (R2=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.