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1.  The association of low socioeconomic status and the risk of having a child with Down syndrome: a report from the National Down Syndrome Project 
Advanced maternal age and altered recombination are known risk factors for Down syndrome cases due to maternal non-disjunction of chromosome 21, whereas the impact of other environmental and genetic factors is unclear. The aim of this study was to investigate an association between low maternal socioeconomic status and chromosome 21 nondisjunction.
Data from 714 case and 977 control families were used to assess chromosome 21 meiosis I and meiosis II nondisjunction errors in the presence of three low socioeconomic status factors: (i) both parents had not completed high school, (ii) both maternal grandparents had not completed high school, and (iii) an annual household income of <$25,000. We applied logistic regression models and adjusted for covariates, including maternal age and race/ethnicity.
As compared with mothers of controls (n = 977), mothers with meiosis II chromosome 21 nondisjunction (n = 182) were more likely to have a history of one low socioeconomic status factor (odds ratio = 1.81; 95% confidence interval = 1.07–3.05) and ≥2 low socioeconomic status factors (odds ratio = 2.17; 95% confidence interval = 1.02–4.63). This association was driven primarily by having a low household income (odds ratio = 1.79; 95% confidence interval = 1.14–2.73). The same statistically significant association was not detected among maternal meiosis I errors (odds ratio = 1.31; 95% confidence interval = 0.81–2.10), in spite of having a larger sample size (n = 532).
We detected a significant association between low maternal socioeconomic status and meiosis II chromosome 21 non-disjunction. Further studies are warranted to explore which aspects of low maternal socioeconomic status, such as environmental exposures or poor nutrition, may account for these results.
PMCID: PMC4122862  PMID: 23558253
chromosome nondisjunction; Down syndrome; risk factors; socioeconomic status; trisomy 21
Evaluate whether there is an association between maternal occupational exposure to polycyclic aromatic hydrocarbons (PAHs) and oral cleftsin offspring. This is the first human study of PAHs and clefts of which the authors are aware.
Case-control study.
Setting, Participants
Data for 1997–2002 from the National Birth Defects Prevention Study, a large population-based case-control study in the US, were analyzed. Maternal telephone interviews yielded information on jobs held in the month before through three months after conception. Two industrial hygienists independently assessed occupational exposure to PAHs ; all jobs rated as exposed or with rating difficulty were reviewed with a third industrial hygienist to reach consensus on all exposure parameters. Logistic regression estimated crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for cleft lip with or without cleft palate (CL±P) and cleft palate alone (CP).
There were 2989 controls( 3.5% exposed), 805 cases of CL±P (5.8% exposed) and 439 cases of CP (4.6% exposed). The odds of maternal occupational exposure to PAH (any vs none) during pregnancy was increased for CL±P cases as compared with controls (OR 1.69, 95% CI 1.18–2.40); the OR was 1.47 (95% CI 1.02–2.12) adjusted for maternal education. There was a statistically significant adjusted exposure-response relationship for CL±P (ptrend = 0.02). ORs for CP were not statistically significant.
Maternal occupational exposure to PAHs was associated with increased risk of cleft lip with or without cleft palate in offspring.
PMCID: PMC4096036  PMID: 23136939
PAHs; polycyclic aromatic hydrocarbons; occupation; malformations; oral clefts
3.  Plasma Lipids, Genetic Variants near APOA1, and the Risk of Infantile Hypertrophic Pyloric Stenosis 
JAMA  2013;310(7):714-721.
Infantile Hypertrophic Pyloric Stenosis (IHPS) is a serious condition in which hypertrophy of the pyloric sphincter muscle layer leads to gastric outlet obstruction. IHPS shows strong familial aggregation and heritability, but knowledge about specific genetic risk variants is limited.
To search the genome comprehensively for genetic associations with IHPS and validate findings in three independent sample sets.
Design, Setting, and Participants
In stage 1, we used reference data from the 1000 Genomes Project for imputation into a genome-wide dataset of 1001 Danish surgery-confirmed cases (diagnosed between 1987–2008) and 2371 disease-free controls. In stage 2, the five most significantly associated loci were tested in independent case-control sample sets from Denmark (cases diagnosed between 1983–2010), Sweden (cases diagnosed between 1958–2011), and the United States (cases diagnosed between 1998–2005) with a total of 1663 cases and 2315 controls.
Main Outcome Measure
Presence of Infantile Hypertrophic Pyloric Stenosis
We found a new genomewide significant locus for IHPS at chromosome 11q23.3. The most significant SNP at the locus, rs12721025 (odds ratio [OR], 1.59; 95% confidence interval [CI], 1.38–1.83, P = 1.9×10−10), is located 301 bases downstream of the Apolipoprotein A-I (APOA1) gene and is correlated (r2 between 0.46 and 0.80) with SNPs previously found to be associated with levels of circulating cholesterol. For these SNPs, the cholesterol lowering allele consistently conferred increased risk of IHPS.
Conclusions and Relevance
We have identified a new genomewide significant locus for IHPS. Characteristics of this locus suggest the possibility of an inverse relationship between levels of circulating cholesterol in neonates and IHPS risk which warrants further investigation.
PMCID: PMC4031654  PMID: 23989729
4.  Preconception folic acid supplementation and risk for chromosome 21 nondisjunction: A report from the National Down Syndrome Project 
Both a lack of maternal folic acid supplementation and the presence of genetic variants that reduce enzyme activity in folate pathway genes have been linked to meiotic nondisjunction of chromosome 21; however, the findings in this area of research have been inconsistent. To better understand these inconsistencies, we asked whether maternal use of a folic acid-containing supplement before conception reduces risk for chromosome 21 nondisjunction. Using questionnaire data from the National Down Syndrome Project, a population-based case-control study, we compared the use of folic acid-containing supplements among mothers of infants with full trisomy 21 due to maternal nondisjunction (n=702) and mothers of infants born with no major birth defects (n=983). Using logistic regression, adjusting for maternal age, race/ethnicity, and infant age at maternal interview, we found no evidence of an association between lack of folic acid supplementation and maternal nondisjunction among all case mothers (OR=1.16; 95% CI: 0.90–1.48). In analyses stratified by meiotic stage and maternal age (<35 years or ≥ 35 years), we found an association among older mothers experiencing meiosis II nondisjunction errors (OR=2.00; 95% CI: 1.08–3.71). These data suggest that lack of folic acid supplementation may be associated specifically with MII errors in the aging oocyte. If confirmed, these results could account for inconsistencies among previous studies, as each study sample may vary by maternal age structure and proportion of meiotic errors.
PMCID: PMC3607196  PMID: 23401135
Down syndrome; Trisomy 21; Aneuploidy; Nondisjunction; Chromosome segregation; Folic acid; Meiosis
5.  Anorectal atresia and variants at predicted regulatory sites in candidate genes 
Annals of human genetics  2012;77(1):31-46.
Anorectal atresia is a serious birth defect of largely unknown etiology but candidate genes have been identified in animal studies and human syndromes. Because alterations in the activity of these genes might lead to anorectal atresia, we selected 71 common variants predicted to be in transcription factor binding sites, CpG windows, splice sites, and miRNA target sites of 25 candidate genes, and tested for their association with anorectal atresia. The study population comprised 150 anorectal atresia cases and 623 control infants without major malformations. Variants predicted to affect transcription factor binding, splicing, and DNA methylation in WNT3A, PCSK5, TCF4, MKKS, GLI2, HOXD12, and BMP4 were associated with anorectal atresia based on a nominal P value <0.05. The GLI2 and BMP4 variants are reported to be moderately associated with gene expression changes (Spearman’s rank correlation coefficients between −0.260 and 0.226). We did not find evidence for interaction between maternal pre-pregnancy obesity and variants in MKKS, a gene previously associated with obesity, on the risk of anorectal atresia. Our results for MKKS support previously suggested associations with anorectal malformations. Our findings suggest that more research is needed to determine whether altered GLI2 and BMP4 expression is important in anorectal atresia in humans.
PMCID: PMC3535506  PMID: 23127126
anorectal malformations; imperforate anus; hindgut; congenital abnormalities
6.  Evaluation of Genes Involved in Limb Development, Angiogenesis, and Coagulation as Risk Factors for Congenital Limb Deficiencies 
We conducted a population-based case-control study of single nucleotide polymorphisms (SNPs) in selected genes to find common variants that play a role in the etiology of limb deficiencies (LD)s. Included in the study were 389 infants with LDs of unknown cause and 980 unaffected controls selected from all births in New York State (NYS) for the years 1998 to 2005. We used cases identified from the NYS Department of Health (DOH) Congenital Malformations Registry. Genotypes were obtained for 132 SNPs in genes involved in limb development (SHH, WNT7A, FGF4, FGF8, FGF10, TBX3, TBX5, SALL4, GREM1, GDF5, CTNNB1, EN1, CYP26A1, CYP26B1), angiogenesis (VEGFA, HIF1A, NOS3), and coagulation (F2, F5, MTHFR). Genotype call rates were >97% and SNPs were tested for departure from Hardy-Weinberg expectations by race/ethnic subgroups. For each SNP, odds ratios (OR)s and confidence intervals (CI)s were estimated and corrected for multiple comparisons for all LDs combined and for LD subtypes. Among non-Hispanic white infants, associations between FGF10 SNPs rs10805683 and rs13170645 and all LDs combined were statistically significant following correction for multiple testing (OR=1.99; 95% CI=1.43-2.77; uncorrected p=0.000043 for rs10805683 heterozygous genotype, and OR=2.37; 95% CI=1.48-3.78; uncorrected p=0.00032 for rs13170645 homozygous minor genotype). We also observed suggestive evidence for associations with SNPs in other genes including CYP26B1 and WNT7A. Animal studies have shown that FGF10 induces formation of the apical ectodermal ridge and is necessary for limb development. Our data suggest that common variants in FGF10 increase the risk for a wide range of non-syndromic limb deficiencies.
PMCID: PMC3448837  PMID: 22965740
limb deficiencies; polymorphisms; FGF10
7.  Nitrosatable drug exposure during the first trimester of pregnancy and selected congenital malformations 
Nitrosatable drugs can react with nitrite in the stomach to form N-nitroso compounds, and results from animal studies suggest that N-nitroso compounds are teratogens. With data from the National Birth Defects Prevention Study, the relation between prenatal exposure to nitrosatable drugs and limb deficiencies, oral cleft, and heart malformations in offspring was examined.
Maternal reports of drugs taken during the first trimester of pregnancy were classified with respect to nitrosatability for mothers of 741 babies with limb deficiencies, 2,774 with oral cleft malformations, 8,091 with congenital heart malformations, and 6,807 without major congenital malformations. Nitrite intake was estimated from maternal responses to a food frequency questionnaire.
Isolated transverse limb deficiencies and atrioventricular septal defects were associated with secondary amine drug exposures (adjusted odds ratios [aOR] 1.51, 95% confidence limit [CI] 1.11, 2.06 and aOR 1.97, 95% CI 1.19, 3.26, respectively). Tertiary amines were associated with hypoplastic left heart syndrome (aOR 1.50, 95% CI 1.10, 2.04) and single ventricle (aOR 1.61, 95% CI 1.06, 2.45). These two malformations were also significantly associated with amide drugs. For several malformations, the strongest associations with nitrosatable drug use occurred among mothers with the highest estimated dietary nitrite intake, especially for secondary amines and atrioventricular septal defects (highest tertile of nitrite, aOR 3.30, 95% CI 1.44, 7.58).
Prenatal exposure to nitrosatable drugs may be associated with several congenital malformations, especially with higher nitrite intake. The possible interaction between nitrosatable drugs and dietary nitrite on risk of congenital malformations warrants further attention.
PMCID: PMC3488451  PMID: 22903972
congenital heart defects; congenital limb deficiency; nitrosatable drug; oral clefts; nitrites
8.  Prenatal Nitrate Intake from Drinking Water and Selected Birth Defects in Offspring of Participants in the National Birth Defects Prevention Study 
Environmental Health Perspectives  2013;121(9):1083-1089.
Background: Previous studies of prenatal exposure to drinking-water nitrate and birth defects in offspring have not accounted for water consumption patterns or potential interaction with nitrosatable drugs.
Objectives: We examined the relation between prenatal exposure to drinking-water nitrate and selected birth defects, accounting for maternal water consumption patterns and nitrosatable drug exposure.
Methods: With data from the National Birth Defects Prevention Study, we linked addresses of 3,300 case mothers and 1,121 control mothers from the Iowa and Texas sites to public water supplies and respective nitrate measurements. We assigned nitrate levels for bottled water from collection of representative samples and standard laboratory testing. Daily nitrate consumption was estimated from self-reported water consumption at home and work.
Results: With the lowest tertile of nitrate intake around conception as the referent group, mothers of babies with spina bifida were 2.0 times more likely (95% CI: 1.3, 3.2) to ingest ≥ 5 mg nitrate daily from drinking water (vs. < 0.91 mg) than control mothers. During 1 month preconception through the first trimester, mothers of limb deficiency, cleft palate, and cleft lip cases were, respectively, 1.8 (95% CI: 1.1, 3.1), 1.9 (95% CI: 1.2, 3.1), and 1.8 (95% CI: 1.1, 3.1) times more likely than control mothers to ingest ≥ 5.42 mg of nitrate daily (vs. < 1.0 mg). Higher water nitrate intake did not increase associations between prenatal nitrosatable drug use and birth defects.
Conclusions: Higher water nitrate intake was associated with several birth defects in offspring, but did not strengthen associations between nitrosatable drugs and birth defects.
Citation: Brender JD, Weyer PJ, Romitti PA, Mohanty BP, Shinde MU, Vuong AM, Sharkey JR, Dwivedi D, Horel SA, Kantamneni J, Huber JC Jr., Zheng Q, Werler MM, Kelley KE, Griesenbeck JS, Zhan FB, Langlois PH, Suarez L, Canfield MA, and the National Birth Defects Prevention Study. 2013. Prenatal nitrate intake from drinking water and selected birth defects in offspring of participants in the National Birth Defects Prevention Study. Environ Health Perspect 121:1083–1089;
PMCID: PMC3764078  PMID: 23771435
9.  A genome-wide association study identifies susceptibility loci for non-syndromic sagittal craniosynostosis near BMP2 and within BBS9 
Nature genetics  2012;44(12):1360-1364.
Sagittal craniosynostosis is the most common form of craniosynostosis, affecting approximately one of 5,000 newborns. We conducted the first genome-wide association study (GWAS) for non-syndromic sagittal craniosynostosis (sNSC) using 130 non-Hispanic white (NHW) case-parent trios. Robust associations were observed in a 120 kb region downstream of BMP2, flanked by rs1884302 (P = 1.13 × 10−14; odds ratio [OR] = 4.58) and rs6140226 (P = 3.40 × 10−11; OR = 0.24) and within a 167 kb region of BBS9 between rs10262453 (P = 1.61 × 10−10; OR=0.19) and rs17724206 (P = 1.50 × 10−8; OR = 0.22). We replicated the associations to both loci [rs1884302 (P = 4.39 × 10−31); rs10262453 (P = 3.50 × 10−14)] in an independent NHW population of 172 unrelated sNSC probands and 548 controls. Both BMP2 and BBS9 are genes with a role in skeletal development warranting functional studies to further understand the etiology of sNSC.
PMCID: PMC3736322  PMID: 23160099
genome-wide association study; non-syndromic sagittal craniosynostosis; BMP2; BBS9; meta-analysis; nonsyndromic
10.  Hirschsprung’s disease and variants in genes that regulate enteric neural crest cell proliferation, migration and differentiation 
Journal of human genetics  2012;57(8):485-493.
Hirschsprung’s disease (HSCR) results from failed colonization of the embryonic gut by enteric neural crest cells (ENCCs); colonization requires RET proto-oncogene (RET) signaling. We sequenced RET to identify coding and splice-site variants in a population-based case group and we tested for associations between HSCR and common variants in RET and candidate genes (ASCL1, HOXB5, L1CAM, PHOX2B, PROK1, PROKR1) chosen because they are involved in ENCC proliferation, migration, and differentiation in animal models. We conducted a nested case-control study of 304 HSCR cases and 1 215 controls. Among 38 (12.5%) cases with 34 RET coding and splice-site variants, 18 variants were previously unreported. We confirmed associations with common variants in HOXB5 and PHOX2B but the associations with variants in ASCL1, L1CAM, and PROK1 were not significant after multiple comparisons adjustment. RET variants were strongly associated with HSCR (P values between 10−3 and 10−31) but this differed by race/ethnicity: associations were absent in African-Americans. Our population-based study not only identified novel RET variants in HSCR cases, it showed that common RET variants may not contribute to HSCR in all race/ethnic groups. The findings for HOXB5 and PHOX2B provide supportive evidence that genes regulating ENCC proliferation, migration, and differentiation could be risk factors for HSCR.
PMCID: PMC3503526  PMID: 22648184
congenital abnormalities; enteric nervous system; Hirschsprung disease; RET
11.  Maternal occupational exposure to organic solvents during early pregnancy and risks of neural tube defects and orofacial clefts 
Though toxicological experiments demonstrate the teratogenicity of organic solvents in animal models, epidemiologic studies have reported inconsistent results. Using data from the population-based National Birth Defects Prevention Study, we examined the relation between maternal occupational exposure to aromatic solvents, chlorinated solvents and Stoddard solvent during early pregnancy and neural tube defects (NTDs) and orofacial clefts (OFCs).
Cases of NTDs (anencephaly, spina bifida and encephalocele) and OFCs (cleft lip ± cleft palate and cleft palate alone) delivered between 1997 and 2002 were identified by birth defect surveillance registries in 8 states; non-malformed control infants were selected using birth certificates or hospital records. Maternal solvent exposure was estimated by industrial hygienist review of self-reported occupational histories in combination with a literature-derived exposure database. Odds ratios (OR) and 95% confidence intervals (CI) for the association between solvent class and each birth defect group and component phenotype were estimated using multivariable logistic regression, adjusting for maternal age, race/ethnicity, education, pre-pregnancy body mass index, folic acid supplement use and smoking.
The prevalence of exposure to any solvent among mothers of NTD cases (n=511), OFC cases (n=1163) and controls (n=2977) was 13.1%, 9.6% and 8.2%, respectively. Exposure to chlorinated solvents was associated with increased odds of NTDs (OR=1.96; CI=1.34, 2.87), especially spina bifida (OR=2.26; CI=1.44, 3.53). No solvent class was strongly associated with OFCs in these data.
Our findings suggest that maternal occupational exposure to chlorinated solvents during early pregnancy is positively associated with the prevalence of NTDs in offspring.
PMCID: PMC3719396  PMID: 22447643
congenital abnormalities; occupational exposure; solvents
12.  Cancer Risk in Children and Adolescents with Birth Defects: A Population-Based Cohort Study 
PLoS ONE  2013;8(7):e69077.
Birth defects are an increasing health priority worldwide, and the subject of a major 2010 World Health Assembly Resolution. Excess cancer risk may be an added burden in this vulnerable group of children, but studies to date have provided inconsistent findings. This study assessed the risk for cancer in children and young adolescents with major birth defects.
Methods and Findings
This retrospective, statewide, population-based, cohort study was conducted in three US states (Utah, Arizona, Iowa). A cohort of 44,151 children and young adolescents (0 through 14 years of age) with selected major, non-chromosomal birth defects or chromosomal anomalies was compared to a reference cohort of 147,940 children without birth defects randomly sampled from each state’s births and frequency matched by year of birth. The primary outcome was rate of cancer prior to age 15 years, by type of cancer and type of birth defect. The incidence of cancer was increased 2.9-fold (95% CI, 2.3 to 3.7) in children with birth defects (123 cases of cancer) compared to the reference cohort; the incidence rates were 33.8 and 11.7 per 100,000 person-years, respectively. However, the excess risk varied markedly by type of birth defect. Increased risks were seen in children with microcephaly, cleft palate, and selected eye, cardiac, and renal defects. Cancer risk was not increased with many common birth defects, including hypospadias, cleft lip with or without cleft palate, or hydrocephalus.
Children with some structural, non-chromosomal birth defects, but not others, have a moderately increased risk for childhood cancer. Information on such selective risk can promote more effective clinical evaluation, counseling, and research.
PMCID: PMC3714243  PMID: 23874873
13.  Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet): Case Definition in Surveillance for Childhood-Onset Duchenne/Becker Muscular Dystrophy 
Journal of child neurology  2010;25(9):1098-1102.
The Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet) is a multisite collaboration to determine the prevalence of childhood-onset Duchenne/Becker muscular dystrophy and to characterize health care and health outcomes in this population. MD STARnet uses medical record abstraction to identify patients with Duchenne/Becker muscular dystrophy born January 1, 1982 or later who resided in one of the participating sites. Critical diagnostic elements of each abstracted record are reviewed independently by ≥4 clinicians and assigned to 1 of 6 case definition categories (definite, probable, possible, asymptomatic, female, not Duchenne/Becker muscular dystrophy) by consensus. As of November 2009, 815 potential cases were reviewed. Of the cases included in analysis, 674 (82%) were either “definite” or “probable” Duchenne/Becker muscular dystrophy. These data reflect a change in diagnostic testing, as case assignment based on genetic testing increased from 67% in the oldest cohort (born 1982–1987) to 94% in the cohort born 2004–2009.
PMCID: PMC3674568  PMID: 20817884
Duchenne muscular dystrophy; Becker muscular dystrophy; diagnostic testing; dystrophin
14.  Maternal dietary intake of nitrates, nitrites and nitrosamines and selected birth defects in offspring: a case-control study 
Nutrition Journal  2013;12:34.
Dietary intake of nitrates, nitrites, and nitrosamines can increase the endogenous formation of N-nitroso compounds in the stomach. Results from animal studies suggest that these compounds might be teratogenic. We examined the relationship between maternal dietary intake of nitrates, nitrites (including plant and animal sources as separate groups), and nitrosamines and several types of birth defects in offspring.
For this population-based case–control study, data from a 58-question food frequency questionnaire, adapted from the short Willett Food Frequency Questionnaire and administered as part of the National Birth Defects Prevention Study (NBDPS), were used to estimate daily intake of dietary nitrates, nitrites, and nitrosamines in a sample of 6544 mothers of infants with neural tube defects (NTD)s, oral clefts (OC)s, or limb deficiencies (LD)s and 6807 mothers of unaffected control infants. Total daily intake of these compounds was divided into quartiles based on the control mother distributions. Odds ratios (OR)s and 95% confidence intervals (CI)s were estimated using logistic regression; estimates were adjusted for maternal daily caloric intake, maternal race-ethnicity, education, dietary folate intake, high fat diet (> 30% of calories from fat), and state of residence.
While some unadjusted ORs for NTDS had 95% (CI)s that excluded the null value, none remained significant after adjustment for covariates, and the effect sizes were small (adjusted odds ratios [aOR] <1.12). Similar results were found for OCs and LDs with the exception of animal nitrites and cleft lip with/without cleft palate (aORs and CIs for quartile 4 compared to quartile 1 =1.24; CI=1.05-1.48), animal nitrites and cleft lip (4th quartile aOR=1.32; CI=1.01-1.72), and total nitrite and intercalary LD (4th quartile aOR=4.70; CI=1.23-17.93).
Overall, odds of NTDs, OCs or LDs did not appear to be significantly associated with estimated dietary intake of nitrate, nitrite, and nitrosamines.
PMCID: PMC3607976  PMID: 23514444
Congenital malformation; Diet; Nitrate; Nitrite; Nitrosamine; Pregnancy
15.  Oral Clefts and Behavioral Health of Young Children 
Oral diseases  2011;18(1):74-84.
This study examined the behavioral health of young children with oral clefts, and effects of satisfaction with facial appearance, cleft-team care, number of cleft-related surgeries and socioeconomic status.
Subjects and Methods
The study included a population-based sample of 104 children ages 2–12 years with isolated oral clefts from the state of Iowa. Behavior was evaluated with the Child Behavior Checklist or the Pediatric Behavior Scale 30, depending on age, compared to normative samples.
Risks of behavioral problems were not significantly different from normative samples except for higher inattention/hyperactivity risks at age 6–12 years. Low satisfaction with facial appearance was associated with behavioral problems in all domains, except aggression. Team-care effects were not associated with behavioral problems. Number of cleft-related surgeries was associated with increased anxiety/depression and somatic symptom risks. Higher socioeconomic status was associated with reduced inattention/hyperactivity, aggressive/oppositional behavior, and somatic symptoms.
Most children with oral clefts may have similar behavioral health outcomes to unaffected children, except for increased inattention/hyperactivity risks at older ages. However, low satisfaction with facial appearance, increased exposure to surgeries and lower socioeconomic status may significantly increase behavioral problems. Also, the findings emphasize the need to study the representation of behavioral health professionals on cleft teams and access to behavioral healthcare.
PMCID: PMC3243788  PMID: 21883709
Oral clefts; cleft lip; cleft palate; behavioral health; child development; cleft team care; socioeconomic status; disparities
16.  Nitrosatable Drug Exposure During Early Pregnancy and Neural Tube Defects in Offspring 
American Journal of Epidemiology  2011;174(11):1286-1295.
Nitrosatable drugs, such as secondary or tertiary amines and amides, form N-nitroso compounds in the presence of nitrite. Various N-nitroso compounds have been associated with neural tube defects in animal models. Using data from the National Birth Defects Prevention Study, the authors examined nitrosatable drug exposure 1 month before and 1 month after conception in 1,223 case mothers with neural tube defect-affected pregnancies and 6,807 control mothers who delivered babies without major congenital anomalies from 1997 to 2005. Nitrite intakes were estimated from mothers’ responses to a food frequency questionnaire. After adjustment for maternal race/ethnicity, educational level, and folic acid supplementation, case women were more likely than were control women to have taken tertiary amines (odds ratio = 1.60, 95% confidence interval (CI): 1.31, 1.95). This association was strongest with anencephalic births (odds ratio = 1.96, 95% CI: 1.40, 2.73); odds ratios associated with tertiary amines from the lowest tertile of nitrite intake to the highest tertile were 1.16 (95% CI: 0.59, 2.29), 2.19 (95% CI: 1.25, 3.86), and 2.51 (95% CI: 1.45, 4.37), respectively. Odds ratios for anencephaly with nitrosatable drug exposure were reduced among women who also took daily vitamin supplements that contained vitamin C. Prenatal exposure to nitrosatable drugs may increase the risk of neural tube defects, especially in conjunction with a mother’s higher dietary intake of nitrites, but vitamin C might modulate this association.
PMCID: PMC3254159  PMID: 22047825
anencephaly; ascorbic acid; neural tube defects; nitrites; nitrosation; pharmaceutical preparations; spinal dysraphism
17.  Lack of maternal folic acid supplementation is associated with heart defects in Down syndrome: a report from the National Down Syndrome Project 
Maternal folic acid supplementation has been associated with a reduced risk for neural tube defects, and may be associated with a reduced risk for congenital heart defects, and other birth defects. Individuals with Down syndrome are at high risk for congenital heart defects and have been shown to have abnormal folate metabolism.
As part of the population-based case-control National Down Syndrome Project, 1011 mothers of infants with Down syndrome reported their use of folic acid-containing supplements. These data were used to determine whether lack of periconceptional maternal folic acid supplementation is associated with congenital heart defects in Down syndrome. We used logistic regression to test the relationship between maternal folic acid supplementation and the frequency of specific heart defects correcting for maternal race/ethnicity, proband sex, maternal use of alcohol and cigarettes, and maternal age at conception.
Lack of maternal folic acid supplementation was more frequent among infants with Down syndrome and atrioventricular septal defects (OR=1.69; 95% CI, 1.08–2.63; P=0.011) or atrial septal defects (OR=1.69; 95% CI, 1.11–2.58; P=0.007) than among infants with Down syndrome and no heart defect. Preliminary evidence suggests that the patterns of association differ by race/ethnicity and sex of the proband. There was no statistically significant association with ventricular septal defects (OR=1.26; 95% CI, 0.85–1.87; P=0.124).
Our results suggest that lack of maternal folic acid supplementation is associated with septal defects in infants with Down syndrome.
PMCID: PMC3233972  PMID: 21987466
Atrial septal defect; Atrioventricular septal defect; Congenital heart defect; Down syndrome; Folic acid
18.  Effect of survey instrument on participation in a follow-up study: a randomization study of a mailed questionnaire versus a computer-assisted telephone interview 
BMC Public Health  2012;12:579.
Many epidemiological and public health surveys report increasing difficulty obtaining high participation rates. We conducted a pilot follow-up study to determine whether a mailed or telephone survey would better facilitate data collection in a subset of respondents to an earlier telephone survey conducted as part of the National Birth Defects Prevention Study.
We randomly assigned 392 eligible mothers to receive a self-administered, mailed questionnaire (MQ) or a computer-assisted telephone interview (CATI) using similar recruitment protocols. If mothers gave permission to contact the fathers, fathers were recruited to complete the same instrument (MQ or CATI) as mothers.
Mothers contacted for the MQ, within all demographic strata examined, were more likely to participate than those contacted for the CATI (86.6% vs. 70.6%). The median response time for mothers completing the MQ was 17 days, compared to 29 days for mothers completing the CATI. Mothers completing the MQ also required fewer reminder calls or letters to finish participation versus those assigned to the CATI (median 3 versus 6), though they were less likely to give permission to contact the father (75.0% vs. 85.8%). Fathers contacted for the MQ, however, had higher participation compared to fathers contacted for the CATI (85.2% vs. 54.5%). Fathers recruited to the MQ also had a shorter response time (median 17 days) and required fewer reminder calls and letters (median 3 reminders) than those completing the CATI (medians 28 days and 6 reminders).
We concluded that offering a MQ substantially improved participation rates and reduced recruitment effort compared to a CATI in this study. While a CATI has the advantage of being able to clarify answers to complex questions or eligibility requirements, our experience suggests that a MQ might be a good survey option for some studies.
PMCID: PMC3506531  PMID: 22849754
19.  Folate and Vitamin B12 Related Genes and Risk for Omphalocele 
Human Genetics  2011;131(5):739-746.
Both taking folic acid-containing vitamins around conception and consuming food fortified with folic acid have been reported to reduce omphalocele rates. Genetic factors are etiologically important in omphalocele as well; our pilot study showed a relationship with the folate metabolic enzyme gene methylenetetrahydrofolate reductase (MTHFR). We studied 169 non-aneuploid omphalocele cases and 761 unaffected, matched controls from all New York State births occurring between 1998 and 2005 to look for associations with single nucleotide polymorphisms (SNPs) known to be important in folate, vitamin B12, or choline metabolism. In the total study population, variants in the transcobalamin receptor gene (TCblR), rs2232775 (Q8R), and the MTHFR gene, rs1801131 (1298A>C), were significantly associated with omphalocele. In African-Americans significant associations were found with SNPs in genes for the vitamin B12 transporter (TCN2) and the vitamin B12 receptor (TCblR). A SNP in the homocysteine-related gene, betaine-homocysteine S-methyltransferase (BHMT), rs3733890 (R239Q), was significantly associated with omphalocele in both African-Americans and Asians. Only the TCblR association in the total population remained statistically significant if Bonferroni correction was applied. The finding that transcobalamin receptor (TCblR) and transporter (TCN2) SNPs and a BHMT SNP were associated with omphalocele suggests that disruption of methylation reactions, in which folate, vitamin B12, and homocysteine play critical parts, may be a risk factor for omphalocele. Our data, if confirmed, suggest that supplements containing both folic acid and vitamin B12 may be beneficial in preventing omphaloceles.
PMCID: PMC3374579  PMID: 22116453
omphalocele; folate; vitamin B12; homocysteine; transcobalamin; transcobalamin receptor
20.  Maternal Occupational Exposure to Polycyclic Aromatic Hydrocarbons: Effects on Gastroschisis among Offspring in the National Birth Defects Prevention Study 
Environmental Health Perspectives  2012;120(6):910-915.
Background: Exposure to polycyclic aromatic hydrocarbons (PAHs) occurs in many occupational settings. There is evidence in animal models that maternal exposure to PAHs during pregnancy is associated with gastroschisis in offspring; however, to our knowledge, no human studies examining this association have been conducted.
Objective: Our goal was to conduct a case–control study assessing the association between estimated maternal occupational exposure to PAHs and gastroschisis in offspring.
Methods: Data from gastroschisis cases and control infants were obtained from the population-based National Birth Defects Prevention Study for the period 1997–2002. Exposure to PAHs was assigned by industrial hygienist consensus, based on self-reported maternal occupational histories from 1 month before conception through the third month of pregnancy. Logistic regression was used to determine the association between estimated occupational PAH exposure and gastroschisis among children whose mothers were employed for at least 1 month during the month before conception through the third month of pregnancy.
Results: The prevalence of estimated occupational PAH exposure was 9.0% in case mothers (27 of 299) and 3.6% in control mothers (107 of 2,993). Logistic regression analyses indicated a significant association between occupational PAHs and gastroschisis among mothers ≥ 20 years of age [odds ratio (OR) = 2.53; 95% confidence interval (CI): 1.27, 5.04] after adjusting for maternal body mass index, education, gestational diabetes, and smoking. This association was not seen in mothers < 20 years (OR = 1.14; 95% CI: 0.55, 2.33), which is notable because although young maternal age is the strongest known risk factor for gastroschisis, most cases are born to mothers ≥ 20 years.
Conclusion: Our findings indicate an association between occupational exposure to PAHs among mothers who are ≥ 20 years and gastroschisis. These results contribute to a body of evidence that PAHs may be teratogenic.
PMCID: PMC3385431  PMID: 22330681
birth defects; gastroschisis; maternal exposure; occupation; PAHs
21.  Descriptive Epidemiology of Clubfoot in Vietnam: A Clinic-Based Study 
The Iowa Orthopaedic Journal  2012;32:120-124.
The prevalence of congenital talipes equinovarus (clubfoot) in Vietnam is estimated to be approximately one in 1000 births. To date, no epidemiological studies have been conducted in this country to assess risk factors associated with this deformity. The purpose of this study was to evaluate specific environmental and socioeconomic factors that may increase the risk of an infant being born with clubfoot. A descriptive clinic-based study was conducted using structured questionnaires given to biological mothers of clinically confirmed clubfoot subjects (n=99) and biological mothers of children between ages 0–18 with no first or second degree family history of clubfoot as controls (n=97). Phenotypic data from clubfoot subjects was also collected. We found that males were twice as likely to have clubfoot and half of clubfoot subjects were affected bilaterally. There was no significant difference in the rate of left versus right clubfoot. Infant and maternal characteristics showing a strong association with clubfoot included breech presentation at birth (p=0.026) and young maternal age (p=0.033). Although there were no strong correlations with any sociodemographic paternal characteristics, a higher percentage of case fathers were younger at the age of conception compared to control fathers. The information from this preliminary study provides a framework for future epidemiologic studies in this population. An understanding of the risk factors associated with clubfoot will play an important role in understanding the pathophysiology of this disabling deformity.
PMCID: PMC3565392  PMID: 23576932
22.  Caffeine, Selected Metabolic Gene Variants, and Risk for Neural Tube Defects 
Investigations of maternal caffeine intake and neural tube defects (NTDs) have not considered genetic influences. Caffeine metabolism gene effects were examined in the National Birth Defects Prevention Study.
Average daily caffeine was summed from self-reported coffee, tea, soda, and chocolate intake for mothers of 768 NTD cases and 4143 controls delivered from 1997–2002. A subset of 306 NTD and 669 control infants and their parents were genotyped for CYP1A2*1F, NAT2 481C>T and NAT2 590G>A. CYP1A2*1F was classified by fast or slow oxidation status and NAT2 variants were categorized into rapid or slow acetylation status. Case-control logistic regression analyses, family-based transmission/disequilibrium tests and log-linear analyses, and hybrid log-linear analyses were conducted to produce odds ratios (OR) or relative risks (RR) and 95% confidence intervals (CI) for caffeine intake and maternal and infant gene variants, and to examine interaction effects.
NTDs were independently associated with infant slow NAT2 acetylator status (RR: 2.00, 95% CI: 1.10–3.64) and maternal CYP1A2*1F fast oxidation status (OR: 1.49 95% CI: 1.10–2.03). Caffeine-consuming mothers who were CYP1A2*1F fast oxidizers and NAT2 slow acetylators had non-significantly elevated estimated risk for an NTD-affected pregnancy (OR: 3.10 95% CI: 0.86–11.21). Multiplicative interaction effects were observed between maternal caffeine and infant CYP1A2*1F fast oxidizer status (pinteraction = 0.03).
The association identified between maternal CYP1A2*1F fast oxidation status and NTDs should be examined further in the context of CYP1A2’s other substrates. Maternal caffeine and its metabolites may be associated with increased risk for NTD-affected pregnancies in genetically susceptible subgroups.
PMCID: PMC2917796  PMID: 20641098
Caffeine; Gene-environment Interaction, Effect Modification; Cytochrome P450 CYP1A2; N-Acetyltransferase NAT2; Embryo, Mammalian; Metabolism; Maternal Exposure/*adverse effects; Neural Tube Defects; Spinal Dysraphism; Encephalocele
23.  Identification of Iowa Live Births in the Agricultural Health Study 
In the Agricultural Health Study, information on participant live births was largely provided by female partners of male private applicators. At the Iowa site, such information was available for 13,599 (42.9%) of 31,707 applicators. To improve identification of live births among Iowa participants, we used a probabilistic and deterministic approach to link available demographic data from 31,707 households and information on live births from 13,599 households with 1,014,916 Iowa birth certificates. Record linkage identified 16,611 (93.7%) of 17,719 reported live births and 17,883 additional live births, most (14,411 or 80.6%) not identified due to non-participation by female partners. This record linkage produced an expanded cohort of live born children among Iowa participants, which will facilitate improved study of the effects of agricultural exposures, including pesticides, on selected birth outcomes and childhood disease.
PMCID: PMC2936500  PMID: 20705576
children; occupational exposures; pesticides; pregnancy; prospective cohort
24.  Challenges and Priorities for Surveillance of Stillbirths: A Report on Two Workshops 
Public Health Reports  2009;124(5):652-659.
Stillbirths, those with and without birth defects, are an important public health topic. The National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention conducted two workshops during April and July 2005. Both workshops explored the challenges of conducting surveillance of stillbirths. Workshop participants considered an approach that added the surveillance of stillbirths, those with and without birth defects, as part of existing population-based birth defects surveillance programs in Iowa and Atlanta. The workshops addressed three key aspects for expanding birth defects programs to conduct active, population-based surveillance on stillbirths: (1) case identification and ascertainment, (2) data collection, and (3) data use and project evaluation. Participants included experts in pediatrics, obstetrics, epidemiology, maternal-fetal medicine, perinatology and pediatric pathology, midwifery, as well as practicing clinicians and pathologists. Expanding existing birth defects surveillance programs to include information of stillbirths could potentially enhance the data available on fetal death reports and also could benefit such programs by improving the ascertainment of birth defects.
PMCID: PMC2728657  PMID: 19753943
25.  Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down Syndrome Projects 
Human genetics  2008;125(1):41-52.
We examined the association between maternal age and chromosome 21 nondisjunction by origin of the meiotic error. We analyzed data from two population-based, case–control studies: Atlanta Down Syndrome Project (1989–1999) and National Down Syndrome Project (2001–2004). Cases were live born infants with trisomy 21 and controls were infants without trisomy 21 delivered in the same geographical regions. We enrolled 1,215 of 1,881 eligible case families and 1,375 of 2,293 controls. We report four primary findings. First, the significant association between advanced maternal age and chromosome 21 nondisjunction was restricted to meiotic errors in the egg; the association was not observed in sperm or in post-zygotic mitotic errors. Second, advanced maternal age was significantly associated with both meiosis I (MI) and meiosis II (MII). For example, compared to mothers of controls, mothers of infants with trisomy 21 due to MI nondisjunction were 8.5 times more likely to be ≥40 years old than 20–24 years old at the birth of the index case (95% CI = 5.6–12.9). Where nondisjunction occurred in MII, mothers were 15.1 times more likely to be ≥40 years (95% CI = 8.4–27.3). Third, the ratio of MI to MII errors differed by maternal age. The ratio was lower among women <19 years of age and those ≥40 years (2.1, 2.3, respectively) and higher in the middle age group (3.6). Lastly, we found no effect of grand-maternal age on the risk for maternal nondisjunction. This study emphasizes the complex association between advanced maternal age and nondisjunction of chromosome 21 during oogenesis.
PMCID: PMC2833410  PMID: 19050929

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