Polymorphisms in thrombophilia and renin-angiotensin system pathways, preterm delivery, and evidence of placental hemorrhage

Association of MTHFR C677T polymorphism with risk of preterm birth in Indian mothers: a case–control study

Background

Since MTHFR is the key enzyme in folate metabolism, its reduction can lead to hyperhomocysteinemia, which can have a negative impact on pregnancy outcome. Moreover, MTHFR polymorphism has also been linked with oxidative stress and genotoxicity. Identifying its ethnicity-specific association can help to reduce the incidence of preterm birth (PTB). Material and methods: Age-matched preterm birth mothers (< 37 weeks) and full-term mothers (> 37 weeks) were carefully selected for the study. The polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method was adopted to analyse MTHFR C677T polymorphism. Oxidative stress (OS) analysis was performed by measuring the levels of antioxidants (superoxide dismutase (SOD) and catalase (CAT)) and OS damage markers (lipid peroxidation (LPO), total protein). Genotoxicity was confirmed by the cytokinesis-block micronucleus cytome (CBMN-Cyt) assay. The statistical analysis was performed by Student’s t test, chi-square test, and one-way ANOVA. The relevant risk of premature delivery was represented by odds ratios (ORs) with 95% confidence intervals (95% CIs).

Results

The MTHFR polymorphism showed statistical significance for PTB outcome with CT and TT genotype frequencies at p < 0.01 and p < 0.05, respectively, between cases and controls. Within the PTB categories (extreme-, very-, moderate-PTB), TT genotype showed statistical significance at (p < 0.05), while CT genotype remained insignificant. Also, statistically high oxidative stress and DNA damage were observed in cases compared to controls for all genotypes. Furthermore, the T allele of the MTHFR gene was found to be linked with significantly increased OS and DNA damage on comparison within the groups.

Conclusions

This study confirms the MTHFR C677T polymorphism, oxidative stress, and genotoxicity biomarkers are associated with the PTB outcome. Analysis of these biomarkers during pregnancy can be of clinical significance.

Relationships between Maternal Gene Polymorphisms in One Carbon Metabolism and Adverse Pregnancy Outcomes: A Prospective Mother and Child Cohort Study in China

Background: To investigate relationships between five single nucleotide polymorphisms (SNP) in four maternal genes involved in one carbon metabolism and adverse pregnancy outcomes, including preterm birth (PTB), low birth weight (LBW), and small-for-gestational-age (SGA). Methods: This was a prospective mother and child cohort study in Wuqiang, China. Pregnant women (n = 939) were recruited from Jun 2016 to Oct 2018. Pregnancy outcomes (PTB, LBW, and SGA) were extracted from medical records and other information including age at childbearing, maternal education level, gravidity, parity, pre-pregnancy weight and height was collected by using a structured questionnaire. The maternal serum folate concentration was measured by using Abbott Architect i2000SR chemiluminescence analyzer in the first prenatal care visit. DNA genotyping of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G, and thymidylate synthetase (TYMS) rs3819102 was processed by Sequenom MassARRAY iPLEX Platform. Univariate and multivariate logistics regression analysis were used to test the relationships between 5 SNPs and PTB, LBW, SGA. Results: Totally, 849 dyads of women and infants were included in the analysis. The prevalence of PTD, LBW, and SGA were 3.76%, 1.58%, and 5.31% respectively. The homozygote frequencies of MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, and TYMS rs3819102 were 44.2%, 1.4%, 6.7%, 1.3%, and 3.2%, and the alt allele frequencies were 66.1%, 10.8%, 24.9%, 10.5%, and 20.5% respectively. The average serum folate concentration was 11.95 ng/mL and the folate deficiency rate was 0.47%. There were no significant associations between MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles and PTD, LBW, SGA (p > 0.05). Conclusions: In the population with adequate folate status and low prevalence of adverse pregnancy outcomes, MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles may not be related to PTD, LBW, and SGA.

Genetic variations of MTHFR gene and their association with preterm birth in Korean women

BACKGROUND AND OBJECTIVE

The MTHFR gene encodes the methylenetetrahydrofolate reductase known to be involved in the homocysteine-methionine pathway. It has been reported that the deficiency of MTHFR activity may cause hyperhomocysteinemia which results in adverse pregnancy outcomes. Previous studies reported a correlation between the MTHFR gene polymorphisms (677 T/C and 1298 A/C) and lower MTHFR activity and its association with preterm birth in various populations. Since these results were conflicting, we analyzed the genetic association of MTHFR gene 677 T/C and 1298 A/C polymorphisms with preterm birth in Korean women.

MATERIALS AND METHODS

The subjects for case-control study were collected a total of 226 Korean women (98 preterm-birth patients and 128 controls). Genotype frequency differences between the case and the control were assessed using chi-square tests. Mann-Whitney t-test was used to estimate the effects of 1298 A/C genotype on clinicopathological characteristics (systolic blood pressure, diastolic blood pressure, birth weight, and gestational age at delivery) in preterm-birth patients.

RESULTS

Our results showed that the MTHFR 677 C/T polymorphism was significantly associated with preterm-birth patients in the analysis of genotype frequency (P=0.044) and the over-dominant model (OR=0.54; 95% CI, 0.320-0.920; P=0.023). The recessive model showed a marginal trend toward significance (OR=0.47; 95% CI, 0.220-1.010; P=0.046). The 1298 A/C polymorphism was also associated with reduced preterm-birth risk in the recessive model (P=0.032). In the correlation analysis, the 1298 C allele was significantly associated with increasing of gestational age at delivery in preterm-birth patients (P=0.034).

CONCLUSIONS

Our findings suggested that the MTHFR gene 677 C/T and 1298 A/C polymorphisms might have protective effects for preterm birth in the Korean women.

Abruptio placentae risk and genetic variations in mitochondrial biogenesis and oxidative phosphorylation: replication of a candidate gene association study

BACKGROUND

Abruptio placentae is a complex multifactorial disease that is associated with maternal and neonatal death and morbidity. Abruptio placentae's high recurrence rate, high prevalence of heritable thrombophilia among women with abruptio placentae, and aggregation of cases in families of women with the disease support the possibility of a genetic predisposition. Previous genome-wide and candidate gene association studies have identified single nucleotide polymorphisms in mitochondrial biogenesis and oxidative phosphorylation genes that potentially are associated with abruptio placentae risk. Perturbations in mitochondrial biogenesis and oxidative phosphorylation, which results in mitochondrial dysfunction, can lead to the impairment of differentiation and invasion of the trophoblast and to several obstetrics complications that include abruptio placentae.

OBJECTIVE

The purpose of this study was to determine whether the results of a candidate genetic association study that indicated a link between DNA variants (implicated in mitochondrial biogenesis and oxidative phosphorylation) and abruptio placentae could be replicated.

STUDY DESIGN

The study was conducted among participants (507 abruptio placentae cases and 1090 control subjects) of the Placental Abruption Genetic Epidemiology study. Weighted genetic risk scores were calculated with the use of abruptio placentae risk-increasing alleles of 11 single nucleotide polymorphisms in 9 mitochondrial biogenesis and oxidative phosphorylation genes (CAMK2B, NR1H3, PPARG, PRKCA, THRB, COX5A, NDUFA10, NDUFA12, and NDUFC2), which previously was reported in the Peruvian Abruptio Placentae Epidemiology study, a study with similar design and study population to the Placental Abruption Genetic Epidemiology study. Logistic regression models were fit to examine associations of weighted genetic risk scores (quartile 1, <25th percentile; quartile 2, 25-50th percentile; quartile 3, 50-70th percentile, and quartile 4, >75th percentile) with risk of abruptio placentae, adjusted for population admixture (the first 4 principal components), maternal age, infant sex, and preeclampsia. The weighted genetic risk score was also modeled as a continuous predictor. To assess potential effect modification, analyses were repeated among strata that were defined by preeclampsia status, maternal age (≥35 vs 18-34 years), and infant sex.

RESULTS

Abruptio placentae cases were more likely to have preeclampsia, shorter gestational age, and lower infant birthweight. Participants in quartile 2 (score, 12.6-13.8), quartile 3 (score, 13.9-15.0) and quartile 4 (score, ≥15.1) had a genetic risk score of 1.45-fold (95% confidence interval, 1.04-2.02; P=.03), a 1.42-fold (95% confidence interval, 1.02-1.98; P=.04), and a 1.75-fold (95% confidence interval, 1.27-2.42; P=7.0E-04) higher odds of abruptio placentae, respectively, compared with those in quartile 1 (score,<12.6; P-for trend=.0003). The risk of abruptio placentae was 1.12-fold (95% confidence interval, 1.05-1.19; P=3.0×10⁰⁴) higher per 1-unit increase in the score. Among women with preeclampsia, those in quartile 4 had a 3.92-fold (95% confidence interval, 1.48-10.36; P=.01) higher odds of abruptio placentae compared with women in quartile 1. Among normotensive women, women in quartile 4 had a 1.57-fold (95% confidence interval, 1.11-2.21; P=.01) higher odds of abruptio placentae compared with those in quartile 1 (P-for interaction=.12). We did not observe differences in associations among strata defined by maternal age or infant sex.

CONCLUSION

In this study, we replicated previous findings and provide strong evidence for DNA variants that encode for genes that are involved in mitochondrial biogenesis and oxidative phosphorylation pathways, which confers risk for abruptio placentae. These results shed light on the mechanisms that implicate DNA variants that encode for proteins in mitochondrial function that are responsible for abruptio placentae risk. Therapeutic efforts to reduce risk of abruptio placentae can be enhanced by improved biologic understanding of maternal mitochondrial biogenesis/oxidative phosphorylation pathways and identification of women who would be at high risk for abruptio placentae.

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.

Association Between Factor V Leiden Mutation, Small for Gestational Age, and Preterm Birth: A Systematic Review and Meta-Analysis

OBJECTIVE

To estimate the association of a maternal factor V Leiden (FVL) mutation with SGA and preterm birth.

DATA SOURCES

We performed a search of PubMed, Embase, Scopus, CINAHL, and the Cochrane Library from inception to April 2016 for cohort and case-control studies of women with FVL mutation and associated outcomes of SGA and preterm birth that included a reference group without FVL mutation. Additional studies were identified from reference lists of relevant research and review articles.

STUDY SELECTION

Two authors (JKB, AMO) independently examined the abstracts of the potentially eligible studies, and full texts of eligible studies were retrieved for further evaluation. Disagreements were resolved by consensus. We identified 42 studies suitable for inclusion in the meta-analysis.

DATA EXTRACTION

Thirty-two studies evaluated SGA, and 18 studies assessed preterm birth. Study quality was assessed using the Newcastle Ottawa Scale. A random effects model with inverse variance weighting was used to calculate pooled ORs and 95% CIs. Subgroup analyses were performed by study design.

DATA SYNTHESIS

The overall OR associating FVL mutation with SGA was significant (OR 1.40, 95% CI 1.18 to 1.67). Analysis of 13 cohort studies resulted in an OR of 1.20 (95% CI 1.03 to 1.41), and data from 19 case-control studies yielded an OR of 1.86 (95% CI 1.35 to 2.56). There was no significant association between FVL mutation and preterm birth (OR 1.17, 95% CI 1.00 to 1.37) when all groups were studied, but the association was significant for case-control studies alone (OR 1.40, 95% CI 1.05 to 1.86).

CONCLUSION

There is an increased risk for SGA in pregnancies complicated by FVL mutation in both cohort and case-control study designs. The risk of preterm birth with FVL mutation is less clear, although there is conflicting evidence from cohort and case-control studies regarding the risk of preterm birth associated with FVL mutation.

Systematic review and meta-analysis of the associations between maternal methylenetetrahydrofolate reductase polymorphisms and preterm delivery

AIM

To date, reported associations between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and preterm delivery are conflicting. The present meta-analysis summarized the existing evidence and evaluated these associations.

METHODS

Eligible studies were retrieved from Medline (PubMed), EMBASE, the Chinese Biomedical Literature Database and the Cochrane Library. We calculated pooled odds ratios (ORs) and 95% confidence interval (CIs) within five genetic models using either random-effects or fixed-effects models dependent on study heterogeneity. Potential publication bias was assessed using a Begg's test. Sensitivity analysis was performed to evaluate the stability of the results.

RESULTS

Thirteen studies involving 4816 mothers who experienced preterm delivery and 34 506 normal controls were finally included. Significant associations between MTHFR C677T polymorphism and the risk of preterm delivery were detected overall (OR_T/C  = 1.34, 95% CI 1.12-1.61; OR_TT/CC  = 1.60, 95% CI 1.21-2.11; OR_CT/CC  = 1.33, 95% CI 1.07-1.65; OR_{TT/(CC + CT)}  = 1.41, 95% CI 1.11-1.78; OR_{(TT + CT)/CC}  = 1.36, 95% CI 1.11-1.66) and in an Asian population (OR_T/C  = 1.80, 95% CI 1.24-2.62; OR_TT/CC  = 2.13, 95% CI 1.27-3.57; OR_CT/CC  = 1.93, 95% CI 1.37-2.71; OR_{(TT + CT)/CC}  = 2.03, 95% CI 1.49-2.77). Negative associations of the A1298C polymorphism were only observed among Asian pregnant women (OR_C/A  = 0.66, 95% CI 0.50-0.88; OR_CC/AA  = 0.10, 95% CI 0.02-0.53; OR_{CC/(AA + AC)}  = 0.11, 95% CI 0.02-0.57; OR_{(CC + AC)/AA}  = 0.68, 95% CI 0.49-0.94).

CONCLUSIONS

MTHFR 677 T may play a significant role in regard to the risk of preterm delivery, especially in the Asian population.

Spontaneous preterm birth and single nucleotide gene polymorphisms: a recent update

Background

Preterm birth (PTB), birth at <37 weeks of gestation, is a significant global public health problem. World-wide, about 15 million babies are born preterm each year resulting in more than a million deaths of children. Preterm neonates are more prone to problems and need intensive care hospitalization. Health issues may persist through early adulthood and even be carried on to the next generation. Majority (70 %) of PTBs are spontaneous with about a half without any apparent cause and the other half associated with a number of risk factors. Genetic factors are one of the significant risks for PTB. The focus of this review is on single nucleotide gene polymorphisms (SNPs) that are reported to be associated with PTB.

Results

A comprehensive evaluation of studies on SNPs known to confer potential risk of PTB was done by performing a targeted PubMed search for the years 2007–2015 and systematically reviewing all relevant studies. Evaluation of 92 studies identified 119 candidate genes with SNPs that had potential association with PTB. The genes were associated with functions of a wide spectrum of tissue and cell types such as endocrine, tissue remodeling, vascular, metabolic, and immune and inflammatory systems.

Conclusions

A number of potential functional candidate gene variants have been reported that predispose women for PTB. Understanding the complex genomic landscape of PTB needs high-throughput genome sequencing methods such as whole-exome sequencing and whole-genome sequencing approaches that will significantly enhance the understanding of PTB. Identification of high risk women, avoidance of possible risk factors, and provision of personalized health care are important to manage PTB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3089-0) contains supplementary material, which is available to authorized users.

Placental genome and maternal-placental genetic interactions: a genome-wide and candidate gene association study of placental abruption

While available evidence supports the role of genetics in the pathogenesis of placental abruption (PA), PA-related placental genome variations and maternal-placental genetic interactions have not been investigated. Maternal blood and placental samples collected from participants in the Peruvian Abruptio Placentae Epidemiology study were genotyped using Illumina's Cardio-Metabochip platform. We examined 118,782 genome-wide SNPs and 333 SNPs in 32 candidate genes from mitochondrial biogenesis and oxidative phosphorylation pathways in placental DNA from 280 PA cases and 244 controls. We assessed maternal-placental interactions in the candidate gene SNPS and two imprinted regions (IGF2/H19 and C19MC). Univariate and penalized logistic regression models were fit to estimate odds ratios. We examined the combined effect of multiple SNPs on PA risk using weighted genetic risk scores (WGRS) with repeated ten-fold cross-validations. A multinomial model was used to investigate maternal-placental genetic interactions. In placental genome-wide and candidate gene analyses, no SNP was significant after false discovery rate correction. The top genome-wide association study (GWAS) hits were rs544201, rs1484464 (CTNNA2), rs4149570 (TNFRSF1A) and rs13055470 (ZNRF3) (p-values: 1.11e-05 to 3.54e-05). The top 200 SNPs of the GWAS overrepresented genes involved in cell cycle, growth and proliferation. The top candidate gene hits were rs16949118 (COX10) and rs7609948 (THRB) (p-values: 6.00e-03 and 8.19e-03). Participants in the highest quartile of WGRS based on cross-validations using SNPs selected from the GWAS and candidate gene analyses had a 8.40-fold (95% CI: 5.8-12.56) and a 4.46-fold (95% CI: 2.94-6.72) higher odds of PA compared to participants in the lowest quartile. We found maternal-placental genetic interactions on PA risk for two SNPs in PPARG (chr3:12313450 and chr3:12412978) and maternal imprinting effects for multiple SNPs in the C19MC and IGF2/H19 regions. Variations in the placental genome and interactions between maternal-placental genetic variations may contribute to PA risk. Larger studies may help advance our understanding of PA pathogenesis.

Placental lesions associated with acute atherosis

OBJECTIVE

Acute atherosis is a lesion of the spiral arteries characterized by fibrinoid necrosis of the vessel wall, an accumulation of fat-containing macrophages, and a mononuclear perivascular infiltrate, which can be found in patients with preeclampsia, fetal death, small-for-gestational age, spontaneous preterm labor/premature prelabor rupture of membrane, and spontaneous mid-trimester abortion. This lesion is thought to decrease blood flow to the intervillous space which may lead to other vascular lesions of the placenta. The objective of this study was to test whether there is an association between acute atherosis and placental lesions that are consistent with maternal vascular underperfusion (MVU), amniotic fluid infection (AFI), fetal vascular thrombo-occlusive disease (FVTOD) or chronic inflammation.

MATERIAL AND METHODS

A retrospective cohort study of pregnant women who delivered between July 1998 and July 2014 at Hutzel Women's Hospital/Detroit Medical Center was conducted examine 16 457 placentas. The frequency of placenta lesions (diagnosed using the criteria of the Perinatal Section of the Society for Pediatric Pathology) was compared between pregnancies with and without acute atherosis.

RESULTS

Among 16 457 women who were enrolled, 10.2% (1671/16 457) were excluded, leaving 14 786 women who contributed data for analysis. Among them, the prevalence of acute atherosis was 2.2% (326/14 786). Women with acute atherosis were more than six times as likely as those without to have placental lesions consistent with maternal underperfusion (adjusted odds ratio - aOR: 6.7; 95% CI 5.2-8.6). To a lesser degree, acute atherosis was also associated with greater risks of having either lesions consistent with FVTOD (aOR 1.7; 95% CI 1.2-2.3) or chronic chorioamnionitis (aOR 1.9; 95% CI 1.3-3), but not with other chronic inflammatory lesions, after adjusting for gestational age at delivery. In contrast, women with acute atherosis were 60% less likely to have lesions consistent with AFI, adjusting for gestational age at delivery (aOR 0.4; 95% CI 0.3-0.5).

CONCLUSIONS

Acute atherosis is associated with increased risks of having placental lesions consistent with MVU, and to a lesser extent, chronic chorioamnionitis and those consistent with FVTOD.

Biological indicators of the in-utero environment and their association with birth weight for gestational age

Birth weight for gestational age (BW/GA) has been associated with a risk of adverse health outcomes. Biological indices of pregnancy complications, maternal mid-pregnancy serum biomarkers and placental pathology may shed light on these associations, but at present, they are most often examined as single entities and offer little insight about overlap. In addition, these indices are typically assessed in relation to the extremes of the BW/GA distribution, leaving open the question of how they relate to the entire BW/GA distribution. Addressing issues such as these may help elucidate why postnatal health outcomes vary across the BW/GA continuum. In this study, we focused on a subset of women who participated in the Pregnancy Outcomes and Community Health Study (n = 1371). We examined BW/GA (i.e. gestational age and sex-referenced z-scores) in relation to obstetric complications, second trimester maternal serum screening results and histologic evidence of placental pathology along with maternal demographics, anthropometrics and substance use. In adjusted models, mean reductions in BW/GA z-scores were associated with preeclampsia (β = -0.70, 95% CI -1.04, -0.36), high maternal serum alpha fetoprotein (β = -0.28, 95% CI -0.43, -0.13), unconjugated estriol (β = -0.31/0.5 multiples of the median decrease, 95% CI -0.41, -0.21) and high levels of maternal obstructive vascular pathology in the placenta (β = -0.46, 95% CI -0.67, -0.25). The findings were similar when preterm infants, small-for-gestational age or large-for-gestational age infants were excluded. More research is needed to examine how the factors studied here might directly mediate or mark risk when evaluating the associations between BW/GA and postnatal health outcomes.

Prevalence of 1691G>A FV mutation in females from Bosnia and Herzegovina--a preliminary report

Factor V is the liver-synthesized multidomain glycoprotein encoded by a gene localised on chromosome 1q23. The point mutation 1691G>A in this gene results in formation of an altered protein of V Factor resistant to activated protein C (APC) cleavage. This mutation alone is the most frequent cause of inborn thrombophilia and the most widely acknowledged genetic risk factor for venous thrombosis in a Caucasian population. This study was designed to provide the first estimate of the frequency of the allele 1691A FV in the Bosnian female population. The 1691G>A FV mutation was examined by polymerase chain reaction-restriction fragment length polymorphism, in a group of 67 women, mean age of 58.6 years with no history of cardiovascular incident. Our findings revealed an absence of the mutated allele 1691A FV in the studied group. This is the first report on the 1691G>A FV mutation in a population from Bosnia and Herzegovina. Further research is needed to establish prevalence of the mutated allele in the population from Bosnia and Herzegovina.

Maternal lipids at mid-pregnancy and the risk of preterm delivery

OBJECTIVE

This study examined associations between maternal lipid levels at mid-pregnancy and preterm delivery, medically indicated or spontaneous.

DESIGN

Prospective cohort study.

SETTING

Women were recruited from 52 clinics in five Michigan, USA communities (1998-2004).

POPULATION

Pregnant women were enrolled at 15-27 weeks' gestation and followed to delivery (n=3019).

METHODS

A single blood sample was obtained at study enrollment. Blood lipids, i.e. total cholesterol (TC), high-density lipoprotein (HDLc), low-density lipoprotein (LDLc) cholesterol, and triglycerides (TG), were measured on a sub-cohort (n=1309).

MAIN OUTCOME MEASURES

There were 221 spontaneous, 100 medically indicated preterm deliveries and 988 term deliveries. Polytomous logistic regression models examined relationships among cholesterol levels (Low: <10(th) percentile, Referent: 10(th) -<70(th) percentile, High: ≥70(th) percentile), quartiles of TG (Referent: first quartile) and delivery outcome (Referent: term).

RESULTS

Odds of medically indicated preterm delivery were increased among women with low TC (adjusted odds ratio (aOR)=2.04, 95% confidence interval (CI): 1.12, 3.72), low HDLc (aOR=1.89, 95%CI: 1.04, 3.42) or low LDLc (aOR=1.96, 95%CI: 1.09, 3.54). Odds of spontaneous preterm delivery were increased among women with high TC (aOR=1.51, 95%CI: 1.06, 2.15), high LDLc (aOR=1.42, 95%CI: 0.99, 2.04) or high TG (aOR=1.90, 95%CI: 1.21, 2.97 and aOR=1.72, 95%CI: 1.06, 2.78 for third and fourth quartiles, respectively).

CONCLUSIONS

Extremely low TC, HDLc, and LDLc were associated with a modest increase in risk of medically indicated preterm delivery, whereas high TC, LDLc and TG modestly increased the risk of spontaneous preterm delivery. Further research is needed to uncover explanations for these associations and to identify optimal ranges for maternal lipids.

Late-preterm birth by delivery circumstance and its association with parent-reported attention problems in childhood

OBJECTIVE

Late-preterm birth (LPB, 34-36 wk) has been associated with an increased risk of attention problems in childhood relative to full-term birth (FTB, ≥37 wk), but little is known about factors contributing to this risk. The authors investigated the contributions of clinical circumstances surrounding delivery using follow-up data from the Pregnancy Outcomes and Community Health (POUCH) Study.

METHODS

Women who delivered late preterm or full term and completed the sex- and age-referenced Conners' Parent Rating Scales-Short Form: Revised were included in the present analysis (N = 762; children's age, 3-9 y). The Conners' Parent Rating Scales-Short Form: Revised measures dimensions of behavior linked to attention problems, including oppositionality, inattention, hyperactivity, and a global attention problem index. Using general linear models, the authors evaluated whether LPB subtype (medically indicated [MI] or spontaneous) was associated with these dimensions relative to FTB.

RESULTS

After adjustment for parity, sociodemographics, child age, and maternal symptoms of depression and serious mental illness during pregnancy and at the child survey, only MI LPB was associated with higher hyperactivity and global index scores (mean difference from FTB = 3.8 [95% confidence interval {CI}: 0.5, 7.0] and 3.1 [95% CI 0.0, 6.2]). These findings were largely driven by children between 6 and 9 years. Removal of women with hypertensive disorders during pregnancy (N = 85) or placental findings related to hypertensive conditions (obstruction, decreased maternal spiral artery conversion; N = 134) reduced the differences below significance thresholds.

CONCLUSIONS

Among LPBs, only MI LPB was associated with higher levels of parent-reported childhood attention problems, suggesting that complications motivating medical intervention during the late-preterm period mark increased risk for such problems. Hypertensive disorders seem to play a role in these associations.

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.

Factor V Leiden as a risk factor for preterm birth--a population-based nested case-control study

BACKGROUND

Preterm birth is a major cause of neonatal morbidity and mortality, occurring in 5-13% of deliveries in developed countries. Genetic thrombophilia can theoretically contribute to the induction of preterm delivery, but the role of thrombophilia as risk factor is unclear.

OBJECTIVES

To assess factor V Leiden, FII G20210A and other selected inherited and acquired variables as risk factors for preterm birth.

PATIENTS/METHODS

We performed a population-based nested case-control study of 100,000 consecutive pregnancies in Finland. Cases and controls were identified by combining national registers. Clinical data were obtained from medical records and standardized questionnaires. We studied 324 cases with preterm delivery at or after 22 and before 37 completed weeks of gestation, and 752 controls.

RESULTS

FV Leiden was associated with a 2.4-fold risk (95% confidence interval [CI] 1.3-4.6) of preterm birth in all pregnancies, and a 2.6-fold risk (95% CI 1.4-5.1) in singleton pregnancies. FV Leiden was especially associated with late preterm birth at or after 32 weeks of pregnancy, with an odds ratio (OR) of 2.9 (95% CI 1.5-5.6) in all pregnancies and an OR of 3.1 (95% CI 1.6-6.2) in singleton pregnancies. FII G20210A was not associated with preterm birth. Twin pregnancy (OR 12.0, 95% CI 6.0-24.1) and a history of venous thrombosis (OR 3.8, 95% CI 1.4-9.8) were associated with increased risk. High educational level and modest overweight (body mass index 25-29.9 kg m(-2) ) had protective effects.

CONCLUSIONS

Maternal carriage of FV Leiden was associated with increased risk of late but not early preterm birth. FII G20120A was not associated with preterm birth.

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.

Evidence of placental haemorrhage and preterm delivery

OBJECTIVE

To evaluate evidence of placental haemorrhage (PH) obtained through maternal interviews, patient charts and placental pathology examinations as potential indicators of a 'bleeding pathway' to preterm delivery (PTD).

DESIGN

Prospective cohort.

SETTING

Fifty-two clinics in five communities in Michigan, USA (1998-2004).

POPULATION

A subset (n = 996) of cohort participants with complete placental pathology data.

METHODS

First-trimester bleeding and placental abruption were ascertained by mid-trimester interviews and chart review, respectively. Disc-impacting blood clot was defined as a gross placental examination finding of a blood clot impacting adjacent tissue. Microscopic haemorrhage was defined as 'high' (top quintile) scores on an aggregate measure of placental pathology findings suggestive of atypical maternal vessel haemorrhage. These four PH indicators were compared with one another and with risk of PTD assessed by logistic regression analyses.

MAIN OUTCOME MEASURES

Preterm delivery and PTD subtypes (i.e. <35 weeks, 35-36 weeks; spontaneous, medically indicated) compared with term deliveries.

RESULTS

Placental abruption cases had 2.3-fold to 5.5-fold increased odds of the other three PH indicators. Disc-impacting blood clots and microscopic haemorrhage were associated with one another (odds ratio [OR] = 4.6), but not with first-trimester bleeding. In a multivariable model that included all four PH indicators and confounders, risk of PTD < 35 weeks was elevated with first-trimester bleeding (OR = 1.9 [1.0, 3.4]), placental abruption (OR = 5.2 [1.7, 16.2]), disc-impacting blood clots (OR = 2.3 [1.0, 5.0]) and microscopic haemorrhage (OR = 2.4 [1.4, 4.2]).

CONCLUSIONS

Multiple clinical and subclinical PH indicators are associated with PTD, particularly early PTD.