Jennita Reefhuis

The wide variety of jobs encountered in population-based studies makes retrospective exposure assessment challenging in occupational epidemiology. In this analysis, two methods for estimating exposure intensity to chlorinated solvents are compared: rated (assigned by an expert rater) and modeled (assigned using statistical models). Estimates of rated and modeled intensities were compared for jobs held by mothers participating in the National Birth Defects Prevention Study with possible exposure to six chlorinated solvents: carbon tetrachloride, chloroform, methylene chloride, perchloroethylene, 1,1,1-trichloroethane, and trichloroethylene. For each possibly exposed job, an industrial hygienist assigned (1) an exposure intensity (rated intensity) and (2) determinants of exposure to be used in a statistical model of exposure intensity (modeled intensity). Of 12,326 reported jobs, between 31 (0.3%) and 746 (6%) jobs were rated as possibly exposed to each of the six solvents. Agreement between rated and modeled intensities was low overall (Spearman correlation coefficient range: −0.09 to 0.28; kappa range: −0.23 to 0.43). Although no air measurements were available to determine if rated or modeled estimates were more accurate, review of participants' job titles showed that modeled estimates were often unexpectedly high given the low-exposure tasks found in these jobs. Differences between the high-exposure jobs used to create the statistical models (obtained from air measurements in the published literature) and the low-exposure jobs in the actual study population is a potential explanation for the disagreement between the two methods. Investigators should be aware that statistical models estimating exposure intensity using existing data from one type of worker population might not be generalizable to all populations of workers.

Although birth defects affect 3% of births, causes are not known for about 66% of cases. Both younger and older maternal age may increase risks for well-known birth defects. The aim of this study was to use current data obtained across the United States to assess the association between maternal age and the risk for birth defects of unknown etiology. The National Birth Defects Prevention Study (NBDPS) is a population-based, case-control study that includes case infants identified through birth defect surveillance systems. Case infants have at least 1 of more than 30 types of major structural birth defects. Control infants have no major birth defects. Mothers were contacted 6 weeks to 24 months after their estimated delivery date (EDD). A standardized telephone interview was conducted to ascertain exposures and behaviors 3 months before and during pregnancy and to obtain information on demographic and lifestyle factors and pregnancy history. Maternal age at EDD was categorized as less than 20, 20 to 24, 25 to 29, 30 to 34, 35 to 39, and 40 years or older. Logistic regression models adjusted for maternal race/ethnicity, education, body mass index, folic acid use, smoking, gravidity, and parental age difference were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) relative to the 25- to 29-year age group. The NBDPS contains interviews from mothers of 23,333 case infants and 8494 control infants for 1997 to 2007. The final sample included 20,377 case and 8169 control infants. The mean and median maternal ages at EDD for case and control mothers were the same at 27.5 years and at 27 years, respectively. Case and control mothers were demographically similar within each age category. The proportion of smokers was 2.5 times higher in mothers younger than 20 years compared with mothers 40 years old; the use of folic acid–containing supplements increased with increasing maternal age. For maternal age younger than 20 years, positive associations were observed for total anomalous pulmonary venous return (aOR, 2.3), amniotic band sequence (aOR, 2.4), and gastroschisis (aOR, 6.1). For the group of mothers 40 years or older, positive associations were observed for tetralogy of Fallot (aOR, 2.2), perimembranous ventricular septal defect (aOR 2.5), atrial septal defect not otherwise specified (aOR, 2.5), and ventricular septal defect plus atrial septal defect association (aOR, 2.9). Noncardiac defects observed in group of mothers 40 years or older were esophageal atresia (aOR, 2.9; 95% CI, 1.7–4.9), hypospadias (aOR, 2.0; 95% CI, 1.4–3.0), and craniosynostosis (aOR, 1.6). For those younger than 20 years, birth defects associated with reduced aORs were cataracts and lens defects (aOR, 0.5), perimembranous ventricular septal defect (aOR, 0.7), left ventricular outflow tract obstruction (aOR, 0.6), coarctation of the aorta (aOR, 0.5), hypospadias (aOR, 0.6), and craniosynostosis (aOR, 0.6). The only birth defect with a reduced aOR seen with increasing maternal age was gastroschisis. For the 30- to 34-year and 35- to 39-year age groups, the aORs were 0.5 and 0.2, respectively; this defect did not appear in the group of mothers 40 years or older. Modifications in lifestyle factors can help to improve infant outcomes. Regardless of age, women who optimize their health before conception and are aware of information on all risks and potential preventions can reduce their risks for birth defects.

BACKGROUND: Birth defects affect 3% of babies born, and are one of the leading causes of infant mortality. Both younger and older maternal age may pose increased risks for certain birth defects. This study assessed the relationship between maternal age at the estimated delivery date and the risk for birth defects. METHODS: Data were obtained from the National Birth Defects Prevention Study, a population‐based case‐control study including mothers across 10 states. Maternal age was stratified into six categories: <20, 20 to 24, 25 to 29, 30 to 34, 35 to 39, and ≥40 years, and also analyzed as a continuous variable. Logistic regression models adjusted formaternal race/ethnicity, education, body mass index (BMI), folic acid use, smoking, gravidity, and parental age difference were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). RESULTS: For maternal age <20 years, associations with total anomalous pulmonary venous return (aOR, 2.3; 95% CI, 1.3–4.0), amniotic band sequence (aOR, 2.4; 95% CI, 1.5–3.8), and gastroschisis (aOR, 6.1; 95% CI, 4.8–8.0) were observed. For the ≥40 year age group, associations with several cardiac defects, esophageal atresia (aOR, 2.9; 95% CI, 1.7–4.9), hypospadias (aOR, 2.0; 95% CI, 1.4–3.0), and craniosynostosis (aOR, 1.6; 95% CI, 1.1–2.4) were observed. Results using maternal age as a continuous variable were consistent with those that used categorized maternal age. CONCLUSION: Elucidating risk factors specific to women ateither extreme of maternal age may offer prevention opportunities. All women should be made aware of prevention opportunities, such as folic acid supplementation, to reduce the occurrence of birth defects. Birth Defects Research (Part A), 2012.

The New Hampshire Birth Conditions Program (NHBCP) is a population-based, active case ascertainment surveillance system that monitors the occurrence of 45 birth defects across the state. A 2008 law requires a new opt-out procedure whereby legal guardians can choose whether or not to have identifiable information retained in the NHBCP database. The purpose of this study was to determine the effects of implementing this opt-out legislation on data collection and surveillance of birth defects by the NHBCP. Using surveillance data collected following implementation of the opt out legislation for the period January 1, 2007, through December 31, 2009, 2 opt-out groups were created: the identifiable information retained (IIR) group, consisting of families who did not choose to opt out, and the de-identified information retained group (DIIR), consisting of those who either chose to opt out or were treated as opt-out birth defect cases because their opt-out package was undeliverable. Descriptive statistics were calculated for each group, and chi-square or Fisher's exact tests were used to compare the proportion of select sociodemographic and medical characteristics between the 2 opt-out groups. Of 776 infants, 120 (15.5%) fell into the DIIR group. Differences were observed by race/ethnicity (among non-Hispanic whites, 15% were in the DIIR group and among Hispanics, 33% were in the DIIR group; p=0.01) and by maternal age (among women 30-34 years of age, 11% were in the DIIR group, and among those 25 years of age or younger, 22% were in the DIIR group; p=0.05). Birth outcomes, payer source, county of residence, and common birth defect diagnoses did not differ between the opt-out groups. This study demonstrated that there were significant differences in race/ethnicity and maternal age between parents who had de-identified information included in the NHBCP compared with those who did not choose to opt out. Although the surveillance of birth defects is not affected, the opportunities for certain types of research will be limited.

Background: In 2004, the Survey on Drug Use and Health showed that 5% of American women reported use of an illicit drug during pregnancy. The results of studies determining the association between periconceptional illicit drug use and birth defects have been inconsistent. Methods: We analyzed data from the National Birth Defects Prevention Study, a case-control study of major birth defects, and assessed all birth defects categories in which there were at least 250 interviewed case mothers. We included 10,241 infants with major congenital malformations (case infants) and 4,967 infants without major congenital malformations (control infants) born between 1997 and 2003 for whom there was a completed maternal interview with detailed information on prenatal illicit drug use and potential confounders. We used multivariable logistic regression to estimate the associations between cannabis, cocaine, and stimulant use in the month before pregnancy or during the first trimester (periconceptional period) and the occurrence of selected birth defects. Results: In the periconceptional period, 5% of the 15,208 mothers reported any use of illicit drugs. We did not find associations between illicit drug use and most of the 20 eligible categories of congenital malformations. Periconceptional cannabis use seemed to be associated with an increased risk of anencephaly (adjusted odds ratio = 1.7; 95% confidence interval = 0.9–3.4), whereas cocaine use in the periconceptional period was associated with the risk of cleft palate (2.5; 1.1–5.4). Conclusions: There were very few suggestions of positive associations between periconceptional illicit drug use and the 20 birth defects categories.

Information regarding the safety of selective serotonin-reuptake inhibitors (SSRIs) in human pregnancy is sparse. Concern has been raised about the risk of congenital heart defects associated with the use of SSRIs in pregnancy.