An investigation into the association among preterm birth, cytokine gene polymorphisms and periodontal disease

Interferon-stimulated gene 15 polymorphisms are associated with spontaneous preterm birth in Taiwanese women

PROBLEM

Immune and inflammatory responses are known to be major causes of preterm birth (PTB). The maternal genetic background plays an important role in the development of PTB. Interferon-stimulated gene 15 (ISG15) is an interferon-induced protein which can modulate immune cell activation and function. We aim to study if polymorphisms in the ISG15 gene are associated with spontaneous PTB (sPTB) risk in Taiwanese women.

METHOD OF STUDY

ISG15 rs4615788 C/G, rs1921 G/A, and rs8997 A/G polymorphisms were genotyped in a hospital-based study of 112 women with sPTB and 1120 term controls. The plasma concentrations of ISG15 were determined by enzyme-linked immunosorbent assay.

RESULTS

We found the ISG15 rs1921 G-rs8997 A haplotype was associated with decreased risk for PTB (χ2  = 6.26, p = .01, pc  = .04). The A/G genotype of ISG15 rs8997 polymorphism might have the potential to confer reduced risk of PTB women (χ2  = 4.09, p = .04, pc  = .08). Spontaneous PTB women displayed higher plasma ISG15 levels compared to term controls (p < .001). The plasma ISG15 levels among pregnant women with rs8997 A/G genotype were found significantly lower compared to G/G genotype (p = .03).

CONCLUSIONS

Women with the ISG15 rs1921 G-rs8997 A haplotype may associate with spontaneous PTB. These findings provide new insights into the etiology of 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.

Risk Factors for Maternal Readmission with Sepsis

OBJECTIVE

Our primary objective was to identify risk factors for maternal readmission with sepsis. Our secondary objectives were to (1) assess diagnoses and infecting organisms at readmission and (2) compare early (<6 weeks) and late (6 weeks to 9 months postpartum) maternal readmission with sepsis.

STUDY DESIGN

We identified our cohort using linked hospital discharge data and birth certificates for California deliveries from 2008 to 2011. Consistent with the 2016 sepsis classification, we defined sepsis as septicemia plus acute organ dysfunction. We compared women with early or late readmission with sepsis to women without readmission with sepsis.

RESULTS

Among 1,880,264 women, 494 (0.03%) were readmitted with sepsis, 61% after 6 weeks. Risk factors for readmission with sepsis included preterm birth, hemorrhage, obesity, government-provided insurance, and primary cesarean. For both early and late sepsis readmissions, the most common diagnoses were urinary tract infection and pyelonephritis, and the most frequently identified infecting organism was gram-negative bacteria. Women with early compared with late readmission with sepsis shared similar obstetric characteristics.

CONCLUSION

Maternal risk factors for both early and late readmission with sepsis included demographic characteristics, cesarean, hemorrhage, and preterm birth. Risks for sepsis after delivery persist beyond the traditional postpartum period of 6 weeks.

Spontaneous preterm birth: advances toward the discovery of genetic predisposition

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.

Mutations in fetal genes involved in innate immunity and host defense against microbes increase risk of preterm premature rupture of membranes (PPROM)

BACKGROUND

Twin studies have revealed a significant contribution of the fetal genome to risk of preterm birth. Preterm premature rupture of membranes (PPROM) is the leading identifiable cause of preterm delivery. Infection and inflammation of the fetal membranes is commonly found associated with PPROM.

METHODS

We carried out whole exome sequencing (WES) of genomic DNA from neonates born of African-American mothers whose pregnancies were complicated by PPROM (76) or were normal term pregnancies (N = 43) to identify mutations in 35 candidate genes involved in innate immunity and host defenses against microbes. Targeted genotyping of mutations in the candidates discovered by WES was conducted on an additional 188 PPROM cases and 175 controls.

RESULTS

We identified rare heterozygous nonsense and frameshift mutations in several of the candidate genes, including CARD6, CARD8, DEFB1, FUT2, MBL2, NLP10, NLRP12, and NOD2. We discovered that some mutations (CARD6, DEFB1, FUT2, MBL2, NLRP10, NOD2) were present only in PPROM cases.

CONCLUSIONS

We conclude that rare damaging mutations in innate immunity and host defense genes, the majority being heterozygous, are more frequent in neonates born of pregnancies complicated by PPROM. These findings suggest that the risk of preterm birth in African-Americans may be conferred by mutations in multiple genes encoding proteins involved in dampening the innate immune response or protecting the host against microbial infection and microbial products.

Genetics, hormonal influences, and preterm birth

Prematurity is a devastating disease with high neonatal morbidity and mortality based on gestational age at birth. Genetic and hormonal signals impact directly on the maternal predisposition to preterm birth or sudden onset of myometrial contractility. Candidate gene or genome-wide approaches are beginning to identify potential variants for women at risk for premature delivery or increased responsiveness to hormonal signals including progesterone. However, a majority of these studies have not yielded definitive results to allow for at this stage for development of personalized therapy.

A Tumor Necrosis Factor—α Promoter Polymorphism and Pregnancy Complications: Results of a Prospective Cohort Study in 1652 Pregnant Women

The purpose of this article is to investigate the frequency of the tumor necrosis factor-alpha (TNF-alpha) -308 G/A single nucleotide polymorphism in women with intrauterine fetal death, preeclampsia, preterm delivery, and small-for-gestational-age (SGA) infants. In a prospective cohort study, DNA from 1652 consecutive pregnant women was analyzed for TNF-alpha -308 G/A by polymerase chain reaction. Women who developed at least 1 of the predefined pregnancy complications were used as cases and compared to women without pregnancy complications. Of 1652 women, 268 (16.2%) developed at least 1 pregnancy complication. TNF-alpha -308 G/A allele frequencies (G: 463/536 [86%] and A: 73/536 [14%] vs G: 2366/2768 [85%] and A: 402/2768 [15%], respectively; P = .6; odds ratio [OR], 0.93; 95% confidence interval [CI], 0.69-1.25) and genotype distributions (G/G+G/A: 259/268 [97%] and A/A 9/268 [3%] vs G/G+G/A: 1352/1384 [98%] and A/A 32/1384 [2%], respectively; P = .4; OR, 0.20; 95% CI, 0.002-14.81) were not significantly different between cases and controls. The authors observed no statistically significant difference in TNF-a -308 G/A genotype distributions comparing controls and women with intrauterine fetal death, preeclampsia, preterm delivery <34 weeks' gestation, preterm delivery >34 weeks' gestation, SGA infants <3rd percentile, and SGA infants of the 4th to 10th percentile. TNF-alpha -308 G/A is not a genetic marker for identifying women at increased risk of common pregnancy complications.

Interleukin-1 receptor antagonist gene polymorphism, adverse pregnancy outcome and periodontitis in Turkish women

OBJECTIVE

The aim of this study was to determine associations between interleukin (IL)-1A (+4845), IL-1B (+3954), and IL-1 receptor antagonist (RN) variable number tandem repeat polymorphisms and adverse pregnancy outcomes and periodontitis in a Turkish women.

DESIGN

A total of 156 patients, including 64 women with normal birth outcome (NB) and 92 women with preterm/low birth weight outcome (PLBW) were included in this case-control study. Within 24h after labor, maternal demographic characteristics and clinical periodontal parameters were recorded. The distribution and genotype frequencies of IL-1 were analyzed with polymerase chain reaction-restriction fragment length polymorphism assay. Statistical analyses were carried out for clinical periodontal parameters, genotype frequencies, and to identify explanatory variables for PLBW.

RESULTS

PLBW was associated with maternal age (p<0.05), irregular prenatal care (p<0.001), previous PLBW (p<0.05), and antibiotic use during pregnancy (p<0.05). Measurements of probing depth and clinical attachment level (CAL) were significantly higher in the PLBW group than in the NB group (p<0.001). PLBW was associated with IL-1RN allele 2 (p<0.001). Moreover, stepwise logistic regression analysis showed that CAL (OR 1.39, 95% CI: 1.04-1.85) and IL-1RN polymorphism (OR 7.92, 95% CI: 2.76-22.79), previous PLBW (OR 5.01, 95% CI: 1.08-23.17), age (OR 1.22, 95% CI: 1.04-1.44) were predictors found to increase the risk of PLBW (p<0.05). There was a negative association between PLBW and regular prenatal care, total number of births, use an antibiotic during pregnancy period (p<0.05).

CONCLUSION

Our study showed that, IL-1RN allele 2, periodontal disease characterized with clinical attachment loss, previous PLBW and age could be an important risk factors for PLBW.

Association between maternal tumor necrosis factor-α G308A polymorphism and interferon-γ A874T polymorphism and risk of preterm birth: a meta-analysis

OBJECTIVE(S)

This article was undertaken to investigate the association between tumor necrosis factor-α (TNF-α) G308A polymorphism and interferon-γ (INF-γ) A874T polymorphism and risk of preterm birth (PTB) by performing a meta-analysis of available studies.

STUDY DESIGN

Articles were chosen based on PubMed, EMBASE, Web of science, and China Biology Medicine (CBM) databases with no language restriction from their inceptions to 1 March, 2014. Specific inclusion criteria were used to evaluate articles. Meta-analysis was performed by using a random or fixed effect model with STATA 11.0 software. We estimated the summary odds ratios (ORs) with its corresponding 95% confidence interval (95%CI) to assess the association.

RESULTS

21 eligible case-control studies with a total of 2103 cases and 5070 controls were finally included into this meta-analysis. Pooled analysis showed that A allele of TNF-α G308A was not associated with increased PTB risk (OR=0.84, 95%CI: 0.65-1.07, p=0.167 for G vs. A). Stratifying analysis for ethnicity and different definition of PTB also indicated that A allele was not associated with increased PTB risk. However, the meta-analysis showed that INF-γ A874T polymorphism was associated with the increased risk of PTB (OR=1.14, 95%CI: 1.11-1.73, p=0.004 for A vs. T). Stratifying analysis was not performed due to the small sample size.

CONCLUSION(S)

TNF-α G308A polymorphism was not associated with an increased risk of PTB, but INF-γ A874T polymorphism may contribute to increasing susceptibility to PTB. Detection of polymorphism of INF-γ A874T might be a promising biomarker for the diagnosis and prognosis of preterm delivery.

A protocol to identify non-classical risk factors for preterm births: the Brazilian Ribeirão Preto and São Luís prenatal cohort (BRISA)

Background

Preterm birth is the main cause of morbidity and mortality during the perinatal period. Classical risk factors are held responsible for only 1/3 of preterm births and no current intervention has produced an appreciable reduction of this event. It is necessary to explore new hypotheses and mechanisms of causality by using an integrated approach, collaboration among research groups and less fragmented theoretical-methodological approaches in order to detect new risk factors and to formulate more effective intervention strategies.

Methods

The study will be conducted on a convenience cohort of Brazilian pregnant women recruited at public and private prenatal health services. A total of 1500 pregnant women in São Luís, and 1500 in Ribeirão Preto, will be invited for an interview and for the collection of biological specimens from the 22nd to the 25th week of gestational age (GA). At the time of delivery they will be reinterviewed. GA will be determined using an algorithm based on two criteria: date of last menstruation (DLM) and obstetric ultrasound (OUS) performed at less than 20 weeks of GA. Illicit drug consumption during pregnancy will be determined using a self-applied questionnaire and the following instruments will be used: perceived stress scale, Beck anxiety scale, screening for depression of the Center of Epidemiological Studies (CES-D), experiences of racial discrimination, social network and social support scale of the Medical Outcomes Study and violence (Abuse Assessment Screening and violence questionnaire of the WHO). Bacterial vaginosis, urinary tract infection and periodontal disease will also be identified. Neuroendocrine, immunoinflammatory and medical intervention hypotheses will be tested. The occurrence of elective cesarean section in the absence of labor will be used as a marker of medical intervention.

Conclusion

Psychosocial, genetic and infectious mechanisms will be selected, since there are indications that they influence preterm birth (PTB). The studies will be conducted in two Brazilian cities with discrepant socioeconomic conditions. The expectation is to identify risk factors for PTB having a greater predictive power than classically studied factors. The final objective is to propose more effective interventions for the reduction of PTB, which, after being tested, might subsidize health policies.

Electronic supplementary material

The online version of this article (doi:10.1186/1742-4755-11-79) contains supplementary material, which is available to authorized users.

The role of genetic polymorphisms in antioxidant enzymes and potential antioxidant therapies in neonatal lung disease

SIGNIFICANCE

Oxidative stress is involved in the development of newborn lung diseases, such as bronchopulmonary dysplasia and persistent pulmonary hypertension of the newborn. The activity of antioxidant enzymes (AOEs), which is impaired as a result of prematurity and oxidative injury, may be further affected by specific genetic polymorphisms or an unfavorable combination of more of them.

RECENT ADVANCES

Genetic polymorphisms of superoxide dismutase and catalase were recently demonstrated to be protective or risk factors for the main complications of prematurity. A lot of research focused on the potential of different antioxidant strategies in the prevention and treatment of lung diseases of the newborn, providing promising results in experimental models.

CRITICAL ISSUES

The effect of different genetic polymorphisms on protein synthesis and activity has been poorly detailed in the newborn, hindering to derive conclusive results from the observed associations with adverse outcomes. Therapeutic strategies that aimed at enhancing the activity of AOEs were poorly studied in clinical settings and partially failed to produce clinical benefits.

FUTURE DIRECTIONS

The clarification of the effects of genetic polymorphisms on the proteomics of the newborn is mandatory, as well as the assessment of a larger number of polymorphisms with a possible correlation with adverse outcome. Moreover, antioxidant treatments should be carefully translated to clinical settings, after further details on optimal doses, administration techniques, and adverse effects are provided. Finally, the study of genetic polymorphisms could help select a specific high-risk population, who may particularly benefit from targeted antioxidant strategies.

Pathway analysis of genetic factors associated with spontaneous preterm birth and pre-labor preterm rupture of membranes

Background

Pre-term birth (PTB) remains the leading cause of infant mortality and morbidity. Its etiology is multifactorial, with a strong genetic component. Genetic predisposition for the two subtypes, spontaneous PTB with intact membranes (sPTB) and preterm prelabor rapture of membranes (PPROM), and differences between them, have not yet been systematically summarised.

Methods and findings

Our literature search identified 15 association studies conducted in 3,600 women on 2175 SNPs in 274 genes. We used Ingenuity software to impute gene pathways and networks related to sPTB and PPROM. Detailed insight in the defined functional ontologies clearly separated integrated datasets for sPTB and PPROM. Our analysis of upstream regulators of genes suggests that glucocorticoid receptor (NR3C1), peroxisome proliferator activated receptor γ (PPARG) and interferon regulating factor 3 (IRF3) may be sPTB specific. PPROM-specific genes may be regulated by estrogen receptor2 (ESR2) and signal transducer and activator of transcription (STAT1). The inflammatory transcription factor NFκB is linked to both sPTB and PPROM, however, their inflammatory response is distinctly different.

Conclusions

Based on our analyses, we propose an autoimmune/hormonal regulation axis for sPTB, whilst pathways implicated in the etiology of PPROM include hematologic/coagulation function disorder, collagen metabolism, matrix degradation and local inflammation. Our hypothesis generating study has identified new candidate genes in the pathogenesis of PPROM and sPTB, which should be validated in large cohorts.

A Genome-Wide Association Study of spontaneous preterm birth in a European population

Background: Preterm birth is defined as a birth prior to 37 completed weeks’ gestation. It affects more than 10% of all births worldwide, and is the leading cause of neonatal mortality in non-anomalous newborns. Even if the preterm newborn survives, there is an increased risk of lifelong morbidity. Despite the magnitude of this public health problem, the etiology of spontaneous preterm birth is not well understood. Previous studies suggest that genetics is an important contributing factor. We therefore employed a genome-wide association approach to explore possible fetal genetic variants that may be associated with spontaneous preterm birth.Methods: We obtained preterm birth phenotype and genotype data from the National Center for Biotechnology Information Genotypes and Phenotypes Database (study accession phs000103.v1.p1). This dataset contains participants collected by the Danish National Birth Cohort and includes 1000 preterm births and 1000 term births as controls. Whole genomes were genotyped on the Illumina Human660W-Quad_v1_A platform, which contains more than 500,000 markers. After data quality control, we performed genome-wide association studies for the 22 autosomal chromosomes.Results: No single nucleotide polymorphism reached genome-wide significance after Bonferroni correction for multiple testing.Conclusion: We found no evidence of genetic association with spontaneous preterm birth in this European population. Approaches that facilitate detection of both common and rare genetic variants, such as evaluation of high-risk pedigrees and genome sequencing, may be more successful in identifying genes associated with spontaneous preterm birth.

The Th1:th2 dichotomy of pregnancy and preterm labour

Pregnancy is a unique immunological state in which a balance of immune tolerance and suppression is needed to protect the fetus without compromising the mother. It has long been established that a bias from the T helper 1 cytokine profile towards the T helper 2 profile contributes towards successful pregnancy maintenance. The majority of publications that report on aberrant Th1:Th2 balance focus on early pregnancy loss and preeclampsia. Over the last few decades, there has been an increased awareness of the role of infection and inflammation in preterm labour, and the search for new biomarkers to predict preterm labour continues. In this paper, we explore the evidence for an aberrant Th1:Th2 profile associated with preterm labour. We also consider the potential for its use in screening women at high risk of preterm labour and for prophylactic therapeutic measures for the prevention of preterm labour and associated neonatal adverse outcomes.

Lactation and neonatal nutrition: defining and refining the critical questions

This paper resulted from a conference entitled "Lactation and Milk: Defining and refining the critical questions" held at the University of Colorado School of Medicine from January 18-20, 2012. The mission of the conference was to identify unresolved questions and set future goals for research into human milk composition, mammary development and lactation. We first outline the unanswered questions regarding the composition of human milk (Section I) and the mechanisms by which milk components affect neonatal development, growth and health and recommend models for future research. Emerging questions about how milk components affect cognitive development and behavioral phenotype of the offspring are presented in Section II. In Section III we outline the important unanswered questions about regulation of mammary gland development, the heritability of defects, the effects of maternal nutrition, disease, metabolic status, and therapeutic drugs upon the subsequent lactation. Questions surrounding breastfeeding practice are also highlighted. In Section IV we describe the specific nutritional challenges faced by three different populations, namely preterm infants, infants born to obese mothers who may or may not have gestational diabetes, and infants born to undernourished mothers. The recognition that multidisciplinary training is critical to advancing the field led us to formulate specific training recommendations in Section V. Our recommendations for research emphasis are summarized in Section VI. In sum, we present a roadmap for multidisciplinary research into all aspects of human lactation, milk and its role in infant nutrition for the next decade and beyond.

California Very Preterm Birth Study: design and characteristics of the population- and biospecimen bank-based nested case-control study

Very preterm birth (VPTB) is a leading cause of infant mortality, morbidity and racial disparity in the US. The underlying causes of VPTB are multiple and poorly understood. The California Very Preterm Birth Study was conducted to discover maternal and infant genetic and environmental factors associated with VPTB. This paper describes the study design, population, data and specimen collection, laboratory methods and characteristics of the study population. Using a large, population-based cohort created through record linkage of livebirths delivered from 2000 to 2007 in five counties of southern California, and existing data and banked specimens from statewide prenatal and newborn screening, 1100 VPTB cases and 796 control mother-infant pairs were selected for study (385/200 White, 385/253 Hispanic and 330/343 Black cases/controls, respectively). Medical record abstraction of cases was conducted at over 50 hospitals to identify spontaneous VPTB, improve accuracy of gestational age, obtain relevant clinical data and exclude cases that did not meet eligibility criteria. VPTB was defined as birth at <32 weeks in Whites and Hispanics and <34 weeks in Blacks. Approximately 55% of all VPTBs were spontaneous and 45% had medical indications or other exclusions. Of the spontaneous VPTBs, approximately 41% were reported to have chorioamnionitis. While the current focus of the California Very Preterm Birth Study is to assess the role of candidate genetic markers on spontaneous VPTB, its design enables the pursuit of other research opportunities to identify social, clinical and biological determinants of different types of VPTB with the ultimate aim of reducing infant mortality, morbidity and racial disparities in these health outcomes in the US and elsewhere.

Systematic identification of spontaneous preterm birth-associated RNA transcripts in maternal plasma

BACKGROUND

Spontaneous preterm birth (SPB, before 37 gestational weeks) is a major cause of perinatal mortality and morbidity, but its pathogenesis remains unclear. Studies on SPB have been hampered by the limited availability of markers for SPB in predelivery clinical samples that can be easily compared with gestational age-matched normal controls. We hypothesize that SPB involves aberrant placental RNA expression, and that such RNA transcripts can be detected in predelivery maternal plasma samples, which can be compared with gestational age-matched controls.

PRINCIPAL FINDINGS

Using gene expression microarray to profile essentially all human genes, we observed that 426 probe signals were changed by >2.9-fold in the SPB placentas, compared with the spontaneous term birth (STB) placentas. Among the genes represented by those probes, we observed an over-representation of functions in RNA stabilization, extracellular matrix binding, and acute inflammatory response. Using RT-quantitative PCR, we observed differences in the RNA concentrations of certain genes only between the SPB and STB placentas, but not between the STB and term elective cesarean delivery placentas. Notably, 36 RNA transcripts were observed at placental microarray signals higher than a threshold, which indicated the possibility of their detection in maternal plasma. Among them, the IL1RL1 mRNA was tested in plasma samples taken from 37 women. It was detected in 6 of 10 (60%) plasma samples collected during the presentation of preterm labor (≤32.9 weeks) in women eventually giving SPB, but was detected in only 1 of 27 (4%) samples collected during matched gestational weeks from women with no preterm labor (Fisher exact test, p = 0.00056).

CONCLUSION

We have identified 36 SPB-associated RNA transcripts, which are possibly detectable in maternal plasma. We have illustrated that the IL1RL1 mRNA was more frequently detected in predelivery maternal plasma samples collected from women resulting in SPB than the gestational-age matched controls.

Immunoregulatory gene polymorphisms in Japanese women with preterm births and periodontitis

Many studies have reported an association between periodontal disease and preterm birth, although this remains controversial. Cytokines and antibodies produced to give resistance to infection can enter the bloodstream and cause preterm labor. We analyzed maternal genetic polymorphisms in various immunoregulatory genes that could affect both preterm birth and periodontitis. A total of 1099 women referred to the Department of Obstetrics and Gynecology, Niigata University Medical and Dental Hospital were candidates for participation, 424 of whom refused, and 553 were excluded. The final number of subjects was 122 (51 with preterm birth, 71 with term birth). Genomic DNA was isolated from venous blood, and 22 polymorphisms were determined: IL-1A, IL-1B, IL-1RN, IL-2, IL-4, IL-6, IL-10, TNFA, TNFRI, TNFRII, FcγRIIA, FcγRIIB, FcγRIIIA, FcγRIIIB, and FcαR. Within five days of labor, periodontal parameters were evaluated, and bacteria from subgingival plaque were detected using real-time PCR. There was no difference in the prevalence and degree of periodontitis between term and preterm births. Chi-squared tests showed that an age <33 years and FcαR(+56)T/C alleles were associated with preterm birth. Multiple logistic regression analysis represented a model with significant fitness in which four variables were associated with preterm birth: maternal age, number of Aggregatibacter actinomycetemcomitans, IL-6(-572)G/C, and FcαR(+56)T/C. In conclusion, there was no association between preterm birth and periodontitis in this study. A. actinomycetemcomitans, IL-6, and FcαR were suggested to be associated with preterm birth. Multiple logistic regression models with both genetic and environmental factors would be useful for evaluating susceptibility to preterm birth.

Genetic variations in fetal and maternal tumor necrosis factor-α and interleukin 10: is there an association with preterm birth or periventricular leucomalacia?

OBJECTIVE

The aim of the study was to identify whether tumor necrosis factor-α (TNF-α) (-308) and interleukin (IL)-10 (-1082; -819) genotypes were associated with preterm delivery and cystic periventricular leucomalacia (PVL).

STUDY DESIGN

Venous blood, buccal swabs or cord blood were collected from mother/child pairs with infants born at term (200) or preterm (106) in the presence and absence of neonatal PVL and of premature infants with PVL (7). Extracted genomic DNA served as template for determination of IL-10 (-1082), IL-10 (-819) and TNF-α (-308) genotypes by allele-specific PCR.

RESULT

No significant difference was observed in the frequencies of IL-10 (-1082), IL-10 (-819) and TNF-α (-308) genotypes in mothers or in children of term versus preterm deliveries with or without PVL.

CONCLUSION

Maternal and infant IL-10 (-1082, -819) and TNF-α (-308) genotypes are not indicative for an increased risk of preterm birth or the development of PVL in premature newborns.

Mapping a new spontaneous preterm birth susceptibility gene, IGF1R, using linkage, haplotype sharing, and association analysis

Preterm birth is the major cause of neonatal death and serious morbidity. Most preterm births are due to spontaneous onset of labor without a known cause or effective prevention. Both maternal and fetal genomes influence the predisposition to spontaneous preterm birth (SPTB), but the susceptibility loci remain to be defined. We utilized a combination of unique population structures, family-based linkage analysis, and subsequent case-control association to identify a susceptibility haplotype for SPTB. Clinically well-characterized SPTB families from northern Finland, a subisolate founded by a relatively small founder population that has subsequently experienced a number of bottlenecks, were selected for the initial discovery sample. Genome-wide linkage analysis using a high-density single-nucleotide polymorphism (SNP) array in seven large northern Finnish non-consanginous families identified a locus on 15q26.3 (HLOD 4.68). This region contains the IGF1R gene, which encodes the type 1 insulin-like growth factor receptor IGF-1R. Haplotype segregation analysis revealed that a 55 kb 12-SNP core segment within the IGF1R gene was shared identical-by-state (IBS) in five families. A follow-up case-control study in an independent sample representing the more general Finnish population showed an association of a 6-SNP IGF1R haplotype with SPTB in the fetuses, providing further evidence for IGF1R as a SPTB predisposition gene (frequency in cases versus controls 0.11 versus 0.05, P = 0.001, odds ratio 2.3). This study demonstrates the identification of a predisposing, low-frequency haplotype in a multifactorial trait using a well-characterized population and a combination of family and case-control designs. Our findings support the identification of the novel susceptibility gene IGF1R for predisposition by the fetal genome to being born preterm.

Cytokine gene polymorphisms and length of gestation

OBJECTIVE

To estimate whether there is an association between length of gestation and gene polymorphisms that effect transcription of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), or interleukin-1β (IL-1β).

METHODS

Blood for DNA analysis was collected from 834 women at high risk enrolled in a randomized, clinical trial of omega-3 fatty acid supplementation for the prevention of recurrent preterm birth. Genotyping was performed for three single nucleotide polymorphisms (SNPs), TNF-α -308, IL-6 -174, and IL-1β +3954. Women with the homozygous minor genotype were compared with women with either the heterozygous or the homozygous major genotype. Kaplan-Meier curves of gestational age at delivery and odds ratios for extreme preterm delivery were adjusted for African-American race and treatment group.

RESULTS

Women who were homozygous for the minor allele at the -308 position in the promoter region of the TNF-α gene had significantly shorter length of gestation than women who were either heterozygous or homozygous for the major allele (adjusted hazard ratio 1.74, 95% confidence interval [CI] 1.04-2.90, P=.03). Among women with this genotype, 20% (3/15) experienced extreme spontaneous preterm delivery (less than 28 weeks of gestation; adjusted odds ratio 7.51, 95% CI 1.84-30.72, P=.005). There was no difference in length of gestation or risk of extreme spontaneous preterm delivery by genotype for the IL-6 -174 or the IL-1β +3954 SNP.

CONCLUSION

Polymorphism at the -308 position in the TNF-α promoter region is associated with shorter gestation and an increased risk of spontaneous extreme preterm delivery.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00135902.

LEVEL OF EVIDENCE

II.

Interplay of cytokine polymorphisms and bacterial vaginosis in the etiology of preterm delivery

Recent findings suggest that the association between inflammation-related genes and preterm delivery may be stronger in the presence of bacterial vaginosis (BV). Tumor necrosis factor-alpha (TNFα) and interleukin 1-beta (IL-1β) are pro-inflammatory cytokines capable of inducing preterm labor in non-human primates. In this study the authors tested associations among two TNFα promoter polymorphisms (-G308A and -G238A), a single IL-1β polymorphism (+C3954T), vaginal microbial findings, and risk of preterm delivery. Data were from the Pregnancy Outcomes and Community Health (POUCH) Study (n=777 term and n=230 preterm deliveries). Vaginal smears collected at mid-pregnancy (15-27 weeks gestation) were scored according to Nugent's criteria. A Nugent score of ≥ 4 was modeled as the cut-point for intermediate and positive BV. Logistic regression was used to estimate odds ratios for associations among independent covariates (vaginal flora, genotype) and preterm delivery. Results showed that women with a Nugent score of≥ 4 and the TNFα -238 A/G or A/A were at increased risk of delivering preterm (race/ethnicity adjusted OR 2.6, 95% CI 1.2, 5.8). The p-value for the genotype and Nugent score interaction=0.02. This study points to one more example of a potential gene-environment interaction in a preterm delivery pathway. Future tests of this finding will determine the robustness of these results.

A genetic association study of maternal and fetal candidate genes that predispose to preterm prelabor rupture of membranes (PROM)

OBJECTIVE

We sought to determine whether maternal/fetal single-nucleotide polymorphisms (SNPs) in candidate genes are associated with preterm prelabor rupture of membranes (pPROM).

STUDY DESIGN

A case-control study was conducted in patients with pPROM (225 mothers and 155 fetuses) and 599 mothers and 628 fetuses with a normal pregnancy; 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; false discovery rate was used to correct for multiple testing (q* = 0.15).

RESULTS

First, a SNP in tissue inhibitor of metalloproteinase 2 in mothers was significantly associated with pPROM (odds ratio, 2.12; 95% confidence interval, 1.47-3.07; P = .000068), and this association remained significant after correction for multiple comparisons. Second, haplotypes for Alpha 3 type IV collagen isoform precursor in the mother were associated with pPROM (global P = .003). Third, multilocus analysis identified a 3-locus model, which included maternal SNPs in collagen type I alpha 2, defensin alpha 5 gene, and endothelin 1.

CONCLUSION

DNA variants in a maternal gene involved in extracellular matrix metabolism doubled the risk of pPROM.

Identification of fetal and maternal single nucleotide polymorphisms in candidate genes that predispose to spontaneous preterm labor with intact membranes

OBJECTIVE

The purpose of this study was to determine whether maternal/fetal single nucleotide polymorphisms (SNPs) in candidate genes are associated with spontaneous preterm labor/delivery.

STUDY DESIGN

A genetic association study was conducted in 223 mothers and 179 fetuses (preterm labor with intact membranes who delivered <37 weeks of gestation [preterm birth (PTB)]), and 599 mothers and 628 fetuses (normal pregnancy); 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; the false discovery rate was used to correct for multiple testing.

RESULTS

The strongest single locus associations with PTB were interleukin-6 receptor 1 (fetus; P=.000148) and tissue inhibitor of metalloproteinase 2 (mother; P=.000197), which remained significant after correction for multiple comparisons. Global haplotype analysis indicated an association between a fetal DNA variant in insulin-like growth factor F2 and maternal alpha 3 type IV collagen isoform 1 (global, P=.004 and .007, respectively).

CONCLUSION

An SNP involved in controlling fetal inflammation (interleukin-6 receptor 1) and DNA variants in maternal genes encoding for proteins involved in extracellular matrix metabolism approximately doubled the risk of PTB.

Chorioamnionitis--a complex pathophysiologic syndrome

Chorioamnionitis, inflammation of the amniochorionic membrane (fetal membranes) is a very common disease but a complex syndrome associated with pregnancy. It presents a clinical impasse due to lack of knowledge of specific etiologies associated with this condition making confident clinical interventions difficult. Recent reports provide insight into genetic, epigenetic, behavioral, psychosocial, molecular and pathophysiological factors that are associated with chorioamnionitis. However, a coordinated approach in understanding causality and lack of early indicators (clinical and biomarkers) has hampered gaining knowledge about the disease status preventing proper intervention. Several reviews have provided in-depth analysis of the histologic and clinical evidence associated with chorioamnionitis. In this review, we provide a novel perspective on chorioamnionitis based on recent evidences from scientific literature on inflammation, apoptosis and genetics.

Cytokine production by peripheral blood mononuclear cells of women with a history of preterm birth

Preterm birth is associated with elevated production of pro-inflammatory cytokines such as TNFalpha at the maternal-fetal interface. Previous studies have suggested that women with a history of preterm birth produce aberrantly strong inflammatory responses to bacterial lipopolysaccharide (LPS). However many intrauterine infections in women are associated with pathogens including Ureaplasma urealyticum, Mycoplasma hominis and Streptococcus agalactiae (group B streptococcus) that contain pro-inflammatory factors other than LPS. We evaluated whether peripheral blood leukocytes from women with a history of preterm birth produce elevated amounts of TNFalpha upon stimulation with pathogens associated with preterm birth and if pre-treatment with aspirin, an anti-inflammatory medication, decreases the ex vivo production of this cytokine. Heat-killed bacteria elicited increased TNFalpha production from leukocytes in a dose-dependent manner, but no differences in TNFalpha production between leukocytes from women with preterm birth and control women with term birth were detected. In women who consumed aspirin each day for one week, TNFalpha production was increased in leukocytes from control women stimulated with Escherichia coli and U. urealyticum, but was reduced or unchanged in leukocytes from women with preterm birth. Similar trends were observed for a subset of samples stimulated with U. urealyticum and assayed for IL-6, IL-10, IL-1beta and TNFalpha by bead array. We conclude that leukocytes from women with a history of preterm birth do not have elevated pro-inflammatory responses to pathogens, and that reproductive history is associated with different effects of aspirin on pro-inflammatory cytokine production.

A novel exonic variant (221delT) in the LGALS13 gene encoding placental protein 13 (PP13) is associated with preterm labour in a low risk population

Predicting adverse pregnancy outcome in low risk patients in a community with poor socio-economic circumstances is difficult, yet about 5% of these pregnancies will result in preterm labour or severe pre-eclampsia. In this study we aimed to identify markers in pro- and anti-inflammatory genes that may contribute to disease and possibly disease prediction in a low risk community setting. A prospective study was undertaken on 450 consecutive low risk primigravid patients. Blood obtained at first booking was screened for known immunological gene variants (IL4 -590, IL1B +3953, IL1RN, IL10 -1082; -819; -592 and TNFA -308; -238; +488) as well as for novel variants in the LGALS13 gene coding for placental protein 13 (PP13). The incidence of preterm labour and pre-eclampsia was 7.1% and 6.8% respectively. A novel exonic variant (221delT) in the LGALS13 gene increased the risk for preterm labour in the total study group (relative risk RR 2.27). Maternal carriage of the interleukin-1 RN*2 allele was associated with an increased risk of hypertension in pregnancy in the Coloured subgroup of the study cohort (RR 2.53). There was an increased risk for preterm labour in the same subgroup with carriage of the TNFA -308 A-allele (TNF2) (RR 2.53). No significance was found for the other variants examined. We conclude that single nucleotide polymorphisms (SNPs) in certain genes regulating implantation and inflammation may contribute to the complex etiology of pre-eclampsia and preterm labour. The association between the 221delT deletion and adverse pregnancy outcome needs to be confirmed in different populations.

Periodontal disease and adverse pregnancy outcomes

Periodontal disease is a common infectious disease in women of reproductive age. The disease is often not diagnosed and in studies of over 10 000 women has been associated with preterm birth, small for gestational age newborns, and preeclampsia. It has been shown in a smaller number of women that treatment of periodontal disease may reduce the rate of preterm birth. The pregnancy complications of periodontal disease may be due to lipopolysaccharide from the periodontal pockets inciting prostaglandin pathways controlling parturition. Three large randomized controlled trials of treatment of periodontal disease are underway and may provide confirmation of the importance of periodontal disease in causing complications of pregnancy.

Spontaneous preterm birth in African Americans is associated with infection and inflammatory response gene variants

OBJECTIVE

The objective of the study was to study the genetic risk factors of spontaneous preterm birth (PTB) in African Americans.

STUDY DESIGN

Case-control analyses were performed using maternal and fetal deoxyribonucleic acid from 279 African American birth events (82 PTB and 197 term) and 1432 single-nucleotide polymorphisms from 130 candidate genes. Single-locus association and haplotype analyses were performed.

RESULTS

The most significant associations were in the maternal interleukin (IL)-15 (rs10833, allele P = 2.91 x 10(-4), genotype P = 2.00 x 10(-3)) gene and the fetal IL-2 receptor B (IL-2RB) (rs84460, allele P = 1.37 x 10(-4), genotype P = 6.29 x 10(-4)) gene. The best models for these markers were additive (rs10833, odds ratio [OR], 0.30; 95% confidence interval [CI], 0.14-0.62; P = 1.0 x 10(-3); rs84460, OR, 2.32; 95% CI, 1.47-3.67; P < 1.0 x 10(-3)). The largest number of significant associations was found in genes related to infection and inflammation. There were overall a larger number of significant associations in infants than in mothers.

CONCLUSION

These results support a strong role for genes involved in infection and inflammation in the pathogenesis of PTB, particularly IL-12 and IL-12RB, and indicate that in African Americans there may be complementarity of maternal and fetal genetic risks for PTB.

A critical assessment of adverse pregnancy outcome and periodontal disease

BACKGROUND

Pre-term birth is a major cause of infant mortality and morbidity that has considerable societal, medical, and economic costs. The rate of pre-term birth appears to be increasing world-wide and efforts to prevent or reduce its prevalence have been largely unsuccessful.

AIM

To review the literature for studies investigating periodontal disease as a possible risk factor for pre-term birth and adverse pregnancy outcomes.

MAIN FINDINGS AND CONCLUSION

Variability among studies in definitions of periodontal disease and adverse pregnancy outcomes as well as widespread inadequate control for confounding factors and possible effect modification make it difficult to base meaningful conclusions on published data. However, while there are indications of an association between periodontal disease and increased risk of adverse pregnancy outcome in some populations, there is no conclusive evidence that treating periodontal disease improves birth outcome. Based on a critical qualitative review, available evidence from clinical trials indicates that, although non-surgical mechanical periodontal treatment in the second trimester of pregnancy is safe and effective in reducing signs of maternal periodontal disease, it does not reduce the rate of pre-term birth. Clinical trials currently underway will further clarify the potential role of periodontal therapy in preventing adverse birth outcomes. Regardless of the outcomes of these trials, it is recommended that large, prospective cohort studies be conducted to assess risk for adverse pregnancy outcome in populations with periodontal disease. It is critical that periodontal exposure and adverse birth outcomes be clearly defined and the many potential confounding factors and possible effect modifiers for adverse pregnancy outcome be controlled in these studies. If periodontal disease is associated with higher risk of adverse pregnancy outcome in these specific populations, large multicenter randomized-controlled trials will be needed to determine if prevention or treatment of periodontal disease, perhaps combined with other interventions, has an effect on adverse pregnancy outcome in these women.

Genetic susceptibility to infection-mediated preterm birth

Preterm birth is a heterogeneous disorder that is responsible for significant neonatal morbidity and mortality. Intrauterine infection is implicated in a significant proportion of preterm birth-particularly in early gestation. Epidemiologic evidence supports a genetic component to infection overall and preterm birth in particular. Furthermore, a number of studies examining genes involved in pathogen recognition and our response to pathogens suggest a genetic susceptibility to infection-mediated preterm birth. On the whole, however, these studies have been difficult to replicate and explain only a small portion of the phenotypic variation in preterm birth. Given this, methodological considerations are emphasized to improve our understanding of the genetic susceptibility to infection-mediated preterm birth.

Genetic contributions to disparities in preterm birth

Ethnic disparity in preterm delivery between African Americans and European Americans has existed for decades, and is likely the consequence of multiple factors, including socioeconomic status, environment, and genetics. This review summarizes existing information on genetic variation and its association with preterm birth in African Americans. Candidate gene-based association studies, in which investigators have evaluated particular genes selected primarily because of their potential roles in the process of normal and pathologic parturition, provide evidence that genetic contributions from both mother and fetus account for some of the disparity in preterm births. To date, most attention has been focused on genetic variation in pro- and anti-inflammatory cytokine genes and their respective receptors. These genes, particularly the pro-inflammatory cytokine genes and their receptors, are linked to matrix metabolism because these cytokines increase expression of matrix degrading metalloproteinases. However, the role that genetic variants that are different between populations play in preterm birth (e.g. the SERPINH1 - G56 SNP) cannot yet be quantified. Future studies based on genome wide association or admixture mapping may reveal other genes that contribute to disparity in prematurity.

Intercellular adhesion molecule-1 K469E polymorphism in Korean patients with spontaneous preterm delivery

OBJECTIVES

To investigate the association between intercellular adhesion molecule-1 (ICAM-1) gene K469E polymorphism and spontaneous preterm delivery in a Korean population.

METHODS

Genomic DNA was extracted from whole blood from 55 women experiencing preterm labor and 153 multiparous women (control group) with a history of at least 2 term deliveries. DNA samples were analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The spontaneous preterm delivery (SPD) group carried the 469E allele significantly more frequently than those in the control group (odds ratio [OR], 1.62; 95% CI, 1.04-2.53). The EE genotype was significantly associated with increased risk of SPD (OR, 2.84; 95% CI, 1.17-6.89; P = 0.02). Allelic frequencies in women with abnormal C-reactive protein levels (K = 0.48; E = 0.52) were significantly different from frequencies in the controls (K = 0.68; E = 0.32) (P = 0.006).

CONCLUSIONS

ICAM-1 gene K469E polymorphism may be a candidate region and useful predictor of susceptibility to SPD in the Korean population.

Genetic regulation of amniotic fluid TNF-alpha and soluble TNF receptor concentrations affected by race and preterm birth

Racial disparity in spontaneous preterm birth (PTB) between African Americans and Caucasians in the US is unexplained, but is probably related to differences in amniotic fluid (AF) inflammatory cytokine profiles. Therefore, this study analyzed the association of 34 single nucleotide polymorphisms (SNPs) in TNF-alpha and its receptor genes (TNFR1 and TNFR2) with AF TNF-alpha and soluble TNF receptor (R1 and R2) concentrations in PTB. Samples consisted of African American and Caucasian cases (PTB), and controls (term birth) for which both cytokine, and maternal and fetal genotype data were available. Analyses were performed with genotype, case, and maker-status interaction in the model for log transformed cytokine concentrations. In Caucasians, two interactions between genotype and pregnancy outcome associated with cytokine concentrations, whereas 14 gene variants in African Americans showed interactions with pregnancy outcome, and 13 showed association with genetic markers. In conclusion, cytokine concentrations in African American preterm births can be partially explained by interactions between pregnancy outcome, SNPs and infection. This does not appear to be the case in Caucasians. These findings may be important in understanding disparity in rates of PTB between the two populations.

Preterm birth and inflammation-The role of genetic polymorphisms

Spontaneous preterm labour and preterm births are still the leading cause of perinatal morbidity and mortality in the developed world. Previous efforts to prevent preterm birth have been hampered by a poor understanding of the underlying pathophysiology, inadequate diagnostic tools and generally ineffective therapies. Clinical, epidemiological and experimental studies indicate that genito-urinary tract infections play a critical role in the pathogenesis of preterm birth. Moreover, intrauterine infection increases perinatal mortality and morbidity, such as cerebral palsy and chronic lung disease, significantly. It has recently been suggested that gene-environment interactions play a significant role in determining the risk of preterm birth. Polymorphisms of certain critical genes may be responsible for a harmful inflammatory response in those who possess them. Accordingly, polymorphisms that increase the magnitude or the duration of the inflammatory response were associated with an increased risk of preterm birth. In contrast polymorphisms that decrease the inflammatory response were associated with a lower risk of preterm birth. This article will review the current understanding of pathogenetic pathways in the aetiology of preterm birth.

Interleukin-6 -174 genotype, periodontal disease and adverse pregnancy outcomes: a pilot study

This study was undertaken to investigate whether maternal periodontal disease and variant genotypes of IL-6 gene are associated with adverse pregnancy outcomes. A total of 145 pregnant women were recruited from St Mary's Hospital, Manchester, UK. Bleeding on probing (BOP) and pocket depth indices were recorded on all teeth. Amplification refractory mutation system-polymerase chain reaction was used for -174 IL-6 genotyping. Birth weight was assessed using the individualized birth ratio (IBR) with intrauterine growth restriction (IUGR) defined as an IBR below the fifth percentile. The G/G genotype results in more BOP % sites in Caucasian (P < 0.001) and Afro-Caribbean pregnant women (P = 0.035). In addition, a marginal significant association between the -174 C/C genotype and IUGR was observed (P = 0.06). The -174* C allele was more frequent in women with IUGR than in normal women (63 vs 37%, P = 0.05). Moreover, the combination between the carriage of -174C allele and increased bleeding sites have increased the risk of IUGR (P = 0.006). Future studies, with a larger sample size, are required to better clarify the relationship between the IL-6 gene polymorphism, periodontal disease, and IUGR.

Heritability of parturition timing: an extended twin design analysis

OBJECTIVE

The objective of the study was to assess relative maternal and paternal genetic influences on birth timing.

STUDY DESIGN

Utilizing The Netherlands Twin Registry, we examined the correlation in birth timing of infants born to monozygotic (MZ) twins and their first-degree relatives (dizygotic twins and siblings of twins). Genetic models estimated the relative influence of genetic and common environmental factors through model fitting of additive genetic (A), common environmental (C), individual-specific environmental factors, and combinations thereof.

RESULTS

We evaluated birth timing correlation among the infants of 1390 twins and their 644 siblings. The correlation in MZ female twins (r = 0.330) was greater than MZ male twins (r = -0.096). Positive correlation were also found in sister-sister pairs (r = 0.223) but not in brother-brother (r = -0.045) or brother-sister pairs (r = -0.038). The most parsimonious AE model indicated a significant maternal contribution of genetic and individual-specific environmental factors to birth timing, but no paternal heritability was demonstrated. Heritability of birth timing in women was 34%; and the remaining variance (66%) was caused by individual-specific environmental factors.

CONCLUSION

Our data implicate a significant contribution of maternal but not paternal genetic influences on birth timing.

Small fetal size before 20 weeks' gestation: associations with maternal tobacco use, early preterm birth, and low birthweight

OBJECTIVE

The objective of the study was to determine whether small fetal size before 20 weeks' gestation is associated with preterm birth (PTB), low birthweight (LBW), and poor fetal growth.

STUDY DESIGN

A total of 4405 singleton pregnancies at 10-19 weeks' gestation (GA) based on a known last menstrual period (LMP) were evaluated. Ultrasound-estimated GA (US-GA) was calculated based on crown-rump length at 10-13 weeks and by femur, head, and abdominal measurements from 14 to 19 weeks. The outcomes were compared between small (1-10 days smaller than LMP-GA) and large (0-10 days larger than LMP-GA) fetuses.

RESULTS

At 10-19 weeks, small fetuses measured 2.7 days younger and were more likely to have mothers who smoked (P = .004). Small fetuses had no more PTB (11.4 vs 12.1%, P = .47) but did have more early PTB before 34 (5.4 vs 4.3%, P = .07) and before 32 weeks (4.1 vs 2.7%, P = .009). Small fetuses had lower birthweights (BWT), more frequent BWT below 2500 g (13.0 vs 8.6%), below 1500 g (4.0 vs 2.4%), and below 1000 g (2.9 vs 1.4%) as well as BWT below 2500 g at term (4.9 vs 2.3%) and BWT less than the 10th percentile (8.8 vs 3.7%), P < or = .003 for each. Small fetuses at 10-19 weeks also had less frequent macrosomia and were less frequently large for gestational age at birth (P < .0001 for each). These findings largely persisted in multivariable analyses.

CONCLUSION

Small fetal size at 10-19 weeks is associated with tobacco use in pregnancy, early PTB, LBW, and poor fetal growth.

Effect of periodontal therapy on pregnancy outcome in women affected by periodontitis

BACKGROUND

There is convincing evidence to suggest that infections affecting the mother during pregnancy may produce alterations in the normal cytokine- and hormone-regulated gestation, which could result in preterm labor, premature rupture of membranes, and preterm birth (PTB). Studies in the late 1990s associated periodontitis with preterm low birth weight (PLBW) deliveries, and this may have similar pathogenic mechanisms as other maternal infections. This study determined the effect of non-surgical periodontal therapy on pregnancy outcome.

METHODS

A total of 200 pregnant women with periodontitis were randomly assigned to treatment and control groups. Detailed data about previous and current pregnancies were obtained. All women received a full-mouth periodontal examination, including oral hygiene index-simplified, bleeding index, and clinical attachment level. The women in the treatment group received non-surgical periodontal therapy during the gestational period, and those in the control group received periodontal treatment after delivery. Periodontal therapy included plaque control instructions and scaling and root planing performed under local anesthesia. The outcome measures assessed were gestational age and birth weight of the infant. PTB was recorded when delivery occurred at <37 weeks of gestation, and low birth weight (LBW) was recorded when the infant weighed<2,500 g.

RESULTS

There were 53 PTBs in the treatment group and 68 PTBs in the control group. Twenty-six LBW infants were recorded in the treatment group, and 48 LBW infants were noted in the control group. The mean gestational ages were 33.8+/-2.8 weeks and 32.7+/-2.8 weeks in the treatment and control groups, respectively. The difference was statistically significant at P<0.006. The mean birth weight was 2,565.3+/-331.2 g in the treatment group and 2,459.6+/-380.7 g in the control group, with the difference being statistically significant at P<0.044. A multiple regression model showed a significant effect of periodontal treatment on birth outcomes.

CONCLUSIONS

Non-surgical periodontal therapy can reduce the risk for preterm births in mothers who are affected by periodontitis. Additional multicentered, randomized, controlled clinical trials are required to confirm this link between periodontitis and PLBW.

Genetic contributions to preterm birth: implications from epidemiological and genetic association studies

Infants born before term (<37 weeks) have an increased risk of neonatal mortality as well as other health problems. The increasing rate of preterm birth in recent decades, despite improvements in health care, creates an impetus to better understand and prevent this disorder. Preterm birth likely depends on a number of interacting factors, including genetic, epigenetic, and environmental risk factors. Genetic studies may identify markers, which more accurately predict preterm birth than currently known risk factors, or novel proteins and/or pathways involved in the disorder. This review summarizes epidemiological and genetic studies to date, emphasizing the complexity of genetic influences on birth timing. While several candidate genes have been reportedly associated with the disorder, inconsistency across studies has been problematic. More systematic and unbiased genetic approaches are needed for future studies to examine the genetic etiology of human birth timing thoroughly.