Dataset Information

Folic Acid and Risk of Preterm Birth: A Meta-Analysis.

ABSTRACT: The results from epidemiologic studies linking blood folate concentrations, folic acid supplementation, or dietary folate to the risk of preterm birth are inconsistent. In this study, we aimed to summarize the available evidence on these associations. A systematic search of the PubMed/MEDLINE, Google Scholar, Web of Science, and Cochrane Library databases up to October 20, 2018 was performed and reference lists of retrieved articles were screened. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for the highest vs. the lowest levels of folate concentrations, folic acid supplementation, and dietary folate were calculated using random-effects models. Subgroup analyses and univariate meta-regression were performed to explore the sources of heterogeneity. Ten studies (six prospective cohort studies and four case-control studies) were included on folate concentrations, 13 cohort studies were included about folic acid supplementation, and 4 cohort studies were included regarding dietary folate intake. Higher maternal folate levels were associated with a 28% reduction in the risk of preterm birth (OR 0.72, 95% CI 0.56-0.93). Higher folic acid supplementation was associated with 10% lower risk of preterm birth (OR 0.90, 95% CI 0.85-0.95). In addition, a significant negative association was observed between dietary folate intake and the risk of preterm birth (OR 0.68, 95% CI 0.55-0.84), but no significant relation was seen between dietary folate and the risk of spontaneous preterm birth (OR 0.89, 95% CI 0.57-1.41). In the subgroup analysis, higher maternal folate levels in the third trimester were associated with a lower risk of preterm birth (OR 0.58, 95% CI 0.36-0.94). To initiate taking folic acid supplementation early before conception was adversely associated with preterm birth risk (OR 0.89, 95% CI 0.83-0.95). In conclusion, higher maternal folate levels and folic acid supplementation were significantly associated with a lower risk of preterm birth. The limited data currently available suggest that dietary folate is associated with a significantly decreased risk of preterm birth.

SUBMITTER: Li B

PROVIDER: S-EPMC6892975 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Folic Acid and Risk of Preterm Birth: A Meta-Analysis.

Li Bingbing B Zhang Xiaoli X Peng Xirui X Zhang Shan S Wang Xiaoyang X Zhu Changlian C

Frontiers in neuroscience 20191128

The results from epidemiologic studies linking blood folate concentrations, folic acid supplementation, or dietary folate to the risk of preterm birth are inconsistent. In this study, we aimed to summarize the available evidence on these associations. A systematic search of the PubMed/MEDLINE, Google Scholar, Web of Science, and Cochrane Library databases up to October 20, 2018 was performed and reference lists of retrieved articles were screened. Pooled odds ratios (ORs) and 95% confidence inte ...[more]

PMID: 31849592

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Project description:Objective To explore if there is an increased cancer risk associated with folic acid supplements given orally. Design Systematic review and meta-analysis of controlled studies of folic acid supplementation in humans reporting cancer incidence and/or cancer mortality. Studies on folic acid fortification of foods were not included. Data sources Cochrane Library, Medline, Embase and Centre of Reviews and Dissemination, clinical trial registries and hand-searching of key journals. Results From 4104 potential references, 19 studies contributed data to our meta-analyses, including 12 randomised controlled trials (RCTs). Meta-analysis of the 10 RCTs reporting overall cancer incidence (N=38?233) gave an RR of developing cancer in patients randomised to folic acid supplements of 1.07 (95% CI 1.00 to 1.14) compared to controls. Overall cancer incidence was not reported in the seven observational studies. Meta-analyses of six RCTs reporting prostate cancer incidence showed an RR of prostate cancer of 1.24 (95% CI 1.03 to 1.49) for the men receiving folic acid compared to controls. No significant difference in cancer incidence was shown between groups receiving folic acid and placebo/control group, for any other cancer type. Total cancer mortality was reported in six RCTs, and a meta-analysis of these did not show any significant difference in cancer mortality in folic acid supplemented groups compared to controls (RR 1.09, 95% CI 0.90 to 1.30). None of the observational studies addressed mortality. Conclusions A meta-analysis of 10 RCTs showed a borderline significant increase in frequency of overall cancer in the folic acid group compared to controls. Overall cancer incidence was not reported in the seven observational studies. Prostate cancer was the only cancer type found to be increased after folic acid supplementation (meta-analyses of six RCTs). Prospective studies of cancer development in populations where food is fortified with folic acid could indicate whether fortification similar to supplementation moderately increases prostate cancer risk.

Project description:BackgroundUterine fibroids may cause preterm birth. This meta-analysis evaluates the effect of uterine fibroids on the risk of preterm birth and other obstetric outcomes.MethodsUsing the literature review method, the databases PubMed, Medline, Embase and Central were retrieved to obtain relevant research literature. The selected studies were analyzed and evaluated. The literature was a cohort study or a case-control study of pregnant women as the research object and uterine fibroids as the exposure factor to observe adverse events during pregnancy. The chi-square test was used to test for heterogeneity. Subgroup analyses were used to explore sources of heterogeneity. Publication bias was assessed using Egger's test. Enumeration data were described by odds ratio (OR). Measurement data were described by mean difference (MD). Calculate the confidence interval (CI).ResultsA total of 11 studies were included in this study, including 7 cohort studies and 4 case-control studies, with a total of 313,913 women. The probability of uterine fibroids among women was 3.99%. The results of meta-analysis showed that women with uterine fibroids experienced preterm birth <37 weeks (OR =1.43, 95% CI: 1.25 to 1.64, P<0.00001), preterm birth <34 weeks (OR =1.73, 95% CI: 1.34 to 2.25, P<0.0001), premature rupture of membranes (OR =1.38, 95% CI: 1.08 to 1.75, P=0.009), placental abruption (OR =1.60, 95% CI: 1.20 to 2.14, P=0.001), cesarean section (OR =2.09, 95% CI: 1.69 to 2.58, P<0.00001), and postpartum hemorrhage (OR =2.95, 95% CI: 1.86 to 4.66, P<0.00001) were all at higher risk, and the mean gestational age at delivery [mean difference (MD) =-0.58, 95% CI: -0.66 to -0.51, P<0.00001] and birth weight (MD =-117.82, 95% CI: -155.19 to -80.45, P<0.00001) were lower. Egger's test indicated that there was no publication bias among the included studies (P>0.05).ConclusionsPregnant women with uterine fibroids are at higher risk for preterm birth and other adverse obstetric outcomes and require closer monitoring.

Project description:Because of the role of inflammation in preterm birth (PTB), polymorphisms in and near the interleukin-6 gene (IL6) have been association study targets. Several previous studies have assessed the association between PTB and a single nucleotide polymorphism (SNP), rs1800795, located in the IL6 gene promoter region. Their results have been inconsistent and SNP frequencies have varied strikingly among different populations. We therefore conducted a meta-analysis with subgroup analysis by population strata to: (1) reduce the confounding effect of population structure, (2) increase sample size and statistical power, and (3) elucidate the association between rs1800975 and PTB.We reviewed all published papers for PTB phenotype and SNP rs1800795 genotype. Maternal genotype and fetal genotype were analyzed separately and the analyses were stratified by population. The PTB phenotype was defined as gestational age (GA) < 37 weeks, but results from earlier GA were selected when available. All studies were compared by genotype (CC versus CG+GG), based on functional studies.For the maternal genotype analysis, 1,165 PTBs and 3,830 term controls were evaluated. Populations were stratified into women of European descent (for whom the most data were available) and women of heterogeneous origin or admixed populations. All ancestry was self-reported. Women of European descent had a summary odds ratio (OR) of 0.68, (95% confidence interval (CI) 0.51 - 0.91), indicating that the CC genotype is protective against PTB. The result for non-European women was not statistically significant (OR 1.01, 95% CI 0.59 - 1.75). For the fetal genotype analysis, four studies were included; there was no significant association with PTB (OR 0.98, 95% CI 0.72 - 1.33). Sensitivity analysis showed that preterm premature rupture of membrane (PPROM) may be a confounding factor contributing to phenotype heterogeneity.IL6 SNP rs1800795 genotype CC is protective against PTB in women of European descent. It is not significant in other heterogeneous or admixed populations, or in fetal genotype analysis.Population structure is an important confounding factor that should be controlled for in studies of PTB.

Dataset Information

Folic Acid and Risk of Preterm Birth: A Meta-Analysis.

Publications

Folic Acid and Risk of Preterm Birth: A Meta-Analysis.

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