Author + information
- Charlotte A. Hobbs, MD, PhD⁎ (, )
- Sadia Malik, MD, MPH,
- Weizhi Zhao, MS,
- S. Jill James, PhD,
- Stepan Melnyk, PhD and
- Mario A. Cleves, PhD
- ↵⁎Arkansas Center for Birth Defects Research and Prevention, 11219 Financial Centre Parkway, Suite 250, Little Rock, Arkansas 72212
To the Editor:An estimated 80% of congenital heart defects result from an interaction between susceptibilities in parental and fetal genomes and environmental exposures including maternal lifestyle factors (1). We and others have recently reported that women who have congenital heart defect-affected pregnancies have alterations in folate metabolism (2). This population-based case-control study was undertaken to determine whether these alterations are associated with specific cardiac phenotypes in their children. The study population, eligibility criteria, and methods have been previously published (2).
Case women had delivered a live-born infant with a non-syndromic septal, conotruncal, or right- or left-sided obstructive defect confirmed by echocardiogram, or surgical or autopsy report reviewed by a pediatric cardiologist. Cases were classified into five defect categories based on anatomical lesion: 1) conotruncal—including transposition of the great arteries, tetralogy of Fallot, truncus arteriosus, double outlet right ventricle, malaligned ventricular septal defect, and interrupted aortic arch type B; 2) septal—including atrial, ventricular, and atrioventricular septal defects; 3) right-sided obstructive—including pulmonary valve stenosis, and pulmonary and tricuspid atresia; 4) left-sided obstructive—including aortic valve stenosis, hypoplastic left heart syndrome and variants, coarctation, and interrupted aortic arch types A and C lesions; and 5) complex cases—combination of three or more of the above cardiac defects.
Control women had delivered infants unaffected by any birth defects. Cases and control patients had completed participation in the National Birth Defects Prevention Study, an ongoing multi-site case-control study investigating the etiology of non-syndromic congenital malformations, including congenital heart defects (3).
During home visits, a nurse obtained written informed consent and a fasting blood sample by routine venipuncture. Plasma biomarker concentrations of homocysteine, methionine, and folate were measured as described elsewhere (2). Case and control women were excluded if pregnant, if taking any known folate-antagonist medications, or if the pregnancy had ended <6 weeks from venipuncture.
Information about the current use of multivitamins, cigarettes, alcohol, dietary and caffeine intake, and lactation status was obtained during home visits. Daily energy and dietary micronutrient intake, including methionine, folate, vitamin B6, and vitamin B12 were estimated using a food-frequency questionnaire (4). The protocol and provisions for informed consent were reviewed and approved by the Institutional Review Board at the University of Arkansas for Medical Sciences.
Plasma biomarker data were log-transformed before analysis. Case and control biomarker concentrations were compared using a Student ttest. Linear regression was used to adjust these comparisons for covariates. Adjusted odds ratios (OR) and corresponding 95% confidence intervals (CI) for the association between plasma biomarkers and cardiac phenotypes status were computed using logistic regression. For each biomarker, quartile cut-points were computed based on the distribution of biomarkers among control patients. Data analyses were performed using the SAS statistical package (version 9.1, SAS Institute, Cary, North Carolina).
A total of 285 congenital heart defect cases and 157 control patients had plasma biomarkers measured. The participation rate was 91.5% for cases and 78.0% for control patients. The most prevalent congenital heart defect phenotype was septal heart defects (43.9%), followed by right-sided obstructive defects (19.3%), and left-sided obstructive defects (14.0%). Only 35 (12.3%) of the case children had conotruncal defects. There were 30 (10.5%) cases that had three or more of the above cardiac defects (complex).
The sample consisted primarily of Caucasian women; 63% of the cases were younger than age 30 years; and <40% reported regular multivitamin use. Nearly 48% of cases consumed alcohol. Smoking was more prevalent among cases than control patients (28.8% vs. 15.3% respectively, p = 0.0016). There were no significant differences between cases and control patients in median dietary and total micronutrient intake from diet plus supplements, including methionine, folate, vitamin B6, and vitamin B12.
Plasma concentrations for homocysteine, methionine, and folate are summarized in Table 1.After controlling for covariates, including maternal age, race, education, smoking, multivitamin supplement intake, alcohol consumption, lactation status, caffeine intake, energy-adjusted dietary folate intake, and the interval between the end of pregnancy and venipuncture, plasma homocysteine levels were significantly elevated in all phenotypes compared with control patients. Women who had children with septal, right-sided, and left-sided obstructive lesions had significantly lower methionine than control patients. Folate levels in women who had pregnancies affected by right-sided obstructive lesions were significantly lower than control patients.
Table 2shows adjusted odds ratios for the association between each biomarker and selected cardiac phenotypes. Among women who had homocysteine concentrations in the highest quartile, the odds of being a case were significantly greater than the odds of being a control. The ORs ranged from 3.69 (95% CI 2.10 to 6.49) for women with children with septal defects to 9.11 (95% CI 3.24 to 25.60) for those with a child with conotruncal defects. For those in the lowest quartile of methionine, the highest OR was observed for women who had a child affected by a left-sided obstructive lesion (OR 3.42; 95% CI 1.55 to 7.55). For women in the lowest quartile of plasma folate distribution, all odds ratios had corresponding 95% CIs that included one.
Our findings indicate that women who had children with congenital heart defects had higher plasma homocysteine concentrations than women without such a history. Among most congenital heart defects, folate intake from diet and supplements was similar between cases and control patients, as was mean plasma folate concentration. Following mandatory food fortification with folic acid, homocysteine may be a more salient marker of increased risk than folate intake or plasma folate concentrations. The mean plasma methionine concentrations were significantly different from control patients among women who had children affected by septal and obstructive defects, but not among those who had children with conotruncal or complex defects.
Important methodologic limitations of our study should be considered. Our intent was to compare plasma biomarker concentrations in women who had a specific congenital heart defect-affected pregnancy compared with control women. Because of limitations in sample sizes for some congenital heart defect phenotypes, we had limited statistical power to detect a difference in plasma biomarker concentration distributions across cardiac phenotypes. Cases had higher participation rates than control patients, and thus factors that determined participation rates may be differentially distributed between cases and control patients. Although plasma biomarkers were not measured at organogenesis, our findings support the hypothesis that imbalances in homocysteine metabolism exist in women with congenital heart defect-affected pregnancies.
Please note: This research is supported by grants from the National Institute of Child Health and Human Development (5R01 HD39054) and the National Center for Research Resources (1C06 RR16517-01 and 3C06 RR16517-01S1), the Centers for Disease Control and Prevention (Cooperative Agreement No. U50/CCU613236), and by the Arkansas Biosciences Institute, the major research component of the Tobacco Settlement Proceeds Act of 2000. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention, the National Institutes of Health, or the Arkansas Biosciences Institute.
- American College of Cardiology Foundation
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- Block Dietary Data Systems