All Publications

  • Greenspace, Air Pollution, Neighborhood Factors, and Preeclampsia in a Population-Based Case-Control Study in California INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH Weber, K. A., Yang, W., Lyons, E., Stevenson, D. K., Padula, A. M., Shaw, G. M. 2021; 18 (10)


    To investigate preeclampsia etiologies, we examined relationships between greenspace, air pollution, and neighborhood factors. Data were from hospital records and geocoded residences of 77,406 women in San Joaquin Valley, California from 2000 to 2006. Preeclampsia was divided into mild, severe, or superimposed onto pre-existing hypertension. Greenspace within 100 and 500 m residential buffers was estimated from satellite data using normalized difference vegetation index (NDVI). Air quality data were averaged over pregnancy from daily 24-h averages of nitrogen dioxide, particulate matter <10 µm (PM10) and <2.5 µm (PM2.5), and carbon monoxide. Neighborhood socioeconomic (SES) factors included living below the federal poverty level and median annual income using 2000 US Census data. Odds of preeclampsia were estimated using logistic regression. Effect modification was assessed using Wald tests. More greenspace (500 m) was inversely associated with superimposed preeclampsia (OR = 0.57). High PM2.5 and low SES were associated with mild and severe preeclampsia. We observed differences in associations between greenspace (500 m) and superimposed preeclampsia by neighborhood income and between greenspace (500 m) and severe preeclampsia by PM10, overall and among those living in higher SES neighborhoods. Less greenspace, high particulate matter, and high-poverty/low-income neighborhoods were associated with preeclampsia, and effect modification was observed between these exposures. Further research into exposure combinations and preeclampsia is warranted.

    View details for DOI 10.3390/ijerph18105127

    View details for Web of Science ID 000654887800001

    View details for PubMedID 34066190

  • Periconceptional stressors and social support and risk for adverse birth outcomes. BMC pregnancy and childbirth Weber, K. A., Carmichael, S. L., Yang, W. n., Tinker, S. C., Shaw, G. M. 2020; 20 (1): 487


    The prevalence of preterm birth and low birth weight has been increasing slightly in recent years. A few studies have suggested that psychosocial stress during pregnancy may increase risk for these adverse birth outcomes. To extend those observations, we analyzed various major life event stressors separately and cumulatively as potential risk factors for preterm birth and low birth weight using granular categories of each outcome in a large, population-based study. Additionally, we assessed if greater social support buffered any effects.Data were from a nested prevalence study of 4395 women in the National Birth Defects Prevention Study who delivered live-born non-malformed infants (controls) between 2006 and 2011. Participants completed a standardized, computer-assisted interview between 6 weeks and 24 months after delivery that included questions on stress and social support from 3 months before pregnancy to the 3rd month of pregnancy. Cumulative stress and support indices were also calculated. Preterm birth was divided into "early preterm" (< 32 weeks), "late preterm" (32-36 weeks) and "term." Low birthweight was divided into "very low birth weight" (< 1500 g), "low birth weight" (1500-2499 g) and "normal birth weight" (≥2500 g). Relative risks and 95% confidence intervals (95% CI) were calculated using Poisson regression.For women reporting relationship difficulties, there was a suggestive risk of early preterm birth (RR: 1.9, 95%CI: 0.9-3.9) and very low birthweight (RR: 2.0, 95%CI: 0.9-4.4). For women reporting that they or someone close to them were victims of abuse, violence, or crime, there was an increased risk of low birthweight (RR: 1.8, 95%CI: 1.1-2.7) and late preterm birth (RR: 1.5, 95%CI: 1.0-2.2). There were no strong associations observed between social support questions and the various outcomes.Our results add some support to prior evidence that certain stressors may be associated with increase selected adverse birth outcomes risk. We did not find strong evidence that social support buffered the observed risks in our study.

    View details for DOI 10.1186/s12884-020-03182-6

    View details for PubMedID 32831042

  • Residential proximity to green space and preeclampsia in California. Environmental epidemiology (Philadelphia, Pa.) Weber, K. A., Lyons, E. n., Yang, W. n., Stevenson, C. n., Stevenson, D. K., Shaw, G. M. 2020; 4 (6): e120


    We investigated whether residing near more green space might reduce the risk of preeclampsia.Participants were women who delivered a live, singleton birth between 1998 and 2011 in eight counties of the San Joaquin Valley in California. There were 7276 cases of preeclampsia divided into mild, severe, or superimposed on preexisting hypertension. Controls were 197,345 women who did not have a hypertensive disorder and delivered between 37 and 41 weeks. Green space was estimated from satellite data using Normalized Difference Vegetation Index (NDVI), an index calculated from surface reflectance at the visible and near-infrared wavelengths. Values closer to 1 denote a higher density of green vegetation. Average NDVI was calculated within a 50 m, 100 m, and 500 m buffer around each woman's residence. Odds ratios and 95% confidence intervals were estimated comparing the lowest and highest quartiles of mean NDVI to the interquartile range comparing each preeclampsia phenotype, divided into early (20-31 weeks) and late (32-36 weeks) preterm birth, to full-term controls.We observed an inverse association in the 500 m buffer for women in the top quartile of NDVI and a positive association for women in the lowest quartile of NDVI for women with superimposed preeclampsia. There were no associations in the 50 and 100 m buffers.Within a 500 m buffer, more green space was inversely associated with superimposed preeclampsia. Future work should explore the mechanism by which green space may protect against preeclampsia.

    View details for DOI 10.1097/EE9.0000000000000120

    View details for PubMedID 33336135

    View details for PubMedCentralID PMC7727466

  • Air Pollution, Maternal Hypertensive Disorders, and Preterm Birth. Environmental epidemiology (Philadelphia, Pa.) Weber, K. A., Yang, W., Lurmann, F., Hammond, S. K., Shaw, G. M., Padula, A. M. 2019; 3 (5)


    Background: Air pollution has been associated with hypertension and preterm birth. We examined if prenatal exposure to air pollutants was associated with gestational hypertension and if its association with preterm birth was modified by maternal hypertension.Methods: Data were from birth certificates and hospital discharge records of 252,205 women in San Joaquin Valley of California from 2000-2006. Air quality data were assigned from 24-hour averages of nitrogen dioxide (NO2), particulate matter <10mum (PM10) and <2.5mum (PM2.5), and carbon monoxide (CO) for different averaging periods over pregnancy. We estimated odds of preterm birth and multiplicative interaction between each pollutant and hypertensive disorder.Results: Among normotensive women, odds of preterm birth were slightly higher for higher exposure to all pollutants over the entire pregnancy. Patterns were similar among women with a hypertensive disorder. Among 32-36 week births there was effect modification for exposure to NO2 and CO during the first trimester with higher odds among hypertensive women, and PM2.5 and CO during the last six weeks with higher odds among normotensive women. For 28-31 week births, there was effect modification by hypertensive status for PM10 exposure for entire pregnancy, first, and second trimester with hypertensive women consistently having lower odds of preterm birth than normotensive.Conclusion: There was some evidence of effect modification in the direction counter to our hypothesis for exposure to PM10 and early preterm birth, and CO and PM2.5 at the end of pregnancy, but overall, hypertension did not modify the relationship between pollution and preterm birth.

    View details for DOI 10.1097/ee9.0000000000000062

    View details for PubMedID 32051927

  • Data-Driven Queries between Medications and Spontaneous Preterm Birth among 2.5 Million Pregnancies: Association with Genital Herpes and Antiviral Drugs. Maric, I., Borisenko, E., Winn, V. D., Weber, K. A., Wong, R. J., Aziz, N., Blumenfeld, Y. J., El-Sayed, Y. Y., Stevenson, D. K., Shaw, G. M. SAGE PUBLICATIONS INC. 2019: 389A
  • Data-driven queries between medications and spontaneous preterm birth among 2.5 million pregnancies. Birth defects research Marić, I. n., Winn, V. D., Borisenko, E. n., Weber, K. A., Wong, R. J., Aziz, N. n., Blumenfeld, Y. J., El-Sayed, Y. Y., Stevenson, D. K., Shaw, G. M. 2019


    Our goal was to develop an approach that can systematically identify potential associations between medication prescribed in pregnancy and spontaneous preterm birth (sPTB) by mining large administrative "claims" databases containing hundreds of medications. One such association that we illustrate emerged with antiviral medications used for herpes treatment.IBM MarketScan® databases (2007-2016) were used. A pregnancy cohort was established using International Classification of Diseases (ICD-9/10) codes. Multiple hypothesis testing and the Benjamini-Hochberg procedure that limited false discovery rate at 5% revealed, among 863 medications, five that showed odds ratios (ORs) <1. The statistically strongest was an association between antivirals and sPTB that we illustrate as a real example of our approach, specifically for treatment of genital herpes (GH). Three groups of women were identified based on diagnosis of GH and treatment during the first 36 weeks of pregnancy: (a) GH without treatment; (b) GH treated with antivirals; (c) no GH or treatment.We identified 2,538,255 deliveries. 0.98% women had a diagnosis of GH. Among them, 60.0% received antiviral treatment. Women with treated GH had OR < 1, (OR [95% CI] = 0.91 [0.85, 0.98]). In contrast, women with untreated GH had a small increased risk of sPTB (OR [95% CI] =1.22 [1.14, 1.32]).Data-driven approaches can effectively generate new hypotheses on associations between medications and sPTB. This analysis led us to examine the association with GH treatment. While unknown confounders may impact these findings, our results indicate that women with untreated GH have a modest increased risk of sPTB.

    View details for DOI 10.1002/bdr2.1580

    View details for PubMedID 31433567

  • A machine learning approach to investigate potential risk factors for gastroschisis in California. Birth defects research Weber, K. A., Yang, W., Carmichael, S. L., Padula, A. M., Shaw, G. M. 2018


    BACKGROUND: To generate new leads about risk factors for gastroschisis, a birth defect that has been increasing in prevalence over time, we performed an untargeted data mining statistical approach.METHODS: Using data exclusively from the California Center of the National Birth Defects Prevention Study, we compared 286 cases of gastroschisis and 1,263 non-malformed, live-born controls. All infants had delivery dates between October 1997 and December 2011 and were stratified by maternal age at birth (<20 and ≥ 20years). Cases and controls were compared by maternal responses to 183 questions (219 variables) using random forest, a data mining procedure. Variables deemed important by random forest were included in logistic regression models to estimate odds ratios and 95% confidence intervals.RESULTS: Among women younger than 20, of variables deemed important, there were higher odds observed for higher consumption of chocolate, low intake of iron, acetaminophen use, and urinary tract infections during the beginning of pregnancy. After adjustment, the higher odds remained for low iron intake and a urinary tract infection in the first month of pregnancy. Among women aged 20 or older, of variables deemed important, higher odds were observed for US-born women of Hispanic ethnicity and for parental substance abuse. There were lower odds observed for obese women, women who ate any cereal the month before pregnancy, and those with higher parity.CONCLUSIONS: We did not discover many previously unreported associations, despite our novel approach to generate new hypotheses. However, our results do add evidence to some previously proposed risk factors.

    View details for PubMedID 30588769

  • An application of data mining to identify potential risk factors for anophthalmia and microphthalmia. Paediatric and perinatal epidemiology Weber, K. A., Yang, W., Carmichael, S. L., Lupo, P. J., Dukhovny, S., Yazdy, M. M., Lin, A. E., Van Bennekom, C. M., Mitchell, A. A., Shaw, G. M., National Birth Defects Prevention Study 2018


    BACKGROUND: We examined a large number of variables to generate new hypotheses regarding a wider range of risk factors for anophthalmia/microphthalmia using data mining.METHODS: Data were from the National Birth Defects Prevention Study, a multicentre, case-control study from 10 centres in the United States. There were 134 cases of "isolated" and 87 "nonisolated" (with other major birth defects) of anophthalmia/microphthalmia and 11052 nonmalformed controls with delivery dates October 1997-December 2011. Using random forest, a data mining procedure, we compared the two case types with controls for 201 variables. Variables considered important ranked by random forest were included in a multivariable logistic regression model to estimate odds ratios and 95% confidence intervals.RESULTS: Predictors for isolated cases included paternal race/ethnicity, maternal intake of certain nutrients and foods, and childhood health problems in relatives. Using regression, inverse associations were observed with greater maternal education and with increasing intake of folate and potatoes. Odds were slightly higher with greater paternal education, for increased intake of carbohydrates and beans, and if relatives had a childhood health problem. For nonisolated cases, predictors included paternal race/ethnicity, maternal intake of certain nutrients, and smoking in the home the month before conception. Odds were higher for Hispanic fathers and smoking in the home and NSAID use the month before conception.CONCLUSIONS: Results appear to support previously hypothesised risk factors, socio-economic status, NSAID use, and inadequate folate intake, and potentially provide new areas such as passive smoking pre-pregnancy, and paternal education and ethnicity, to explore for further understanding of anophthalmia/microphthalmia.

    View details for PubMedID 30300919

  • Epidemiology of anophthalmia and microphthalmia: Prevalence and patterns in Texas, 1999-2009 AMERICAN JOURNAL OF MEDICAL GENETICS PART A Chambers, T. M., Agopian, A. J., Lewis, R. A., Langlois, P. H., Danysh, H. E., Weber, K. A., Shaw, G. M., Mitchell, L. E., Lupo, P. J. 2018; 176 (9): 1810–18


    Anophthalmia and microphthalmia are a set of rare, yet severe, birth defects considered to be part of a spectrum of developmental ocular malformations ranging from smaller than average to completely absent eyes. Despite their clinical significance, little is known about the etiologies of these conditions. The goal of this study was to expand our understanding of the epidemiology of anophthalmia and microphthalmia. Data for this population-based assessment were obtained from the Texas Birth Defects Registry (TBDR) and Center for Health Statistics for the period 1999-2009. Descriptive analyses and estimates of birth prevalence and prevalence ratios (PR) were determined for this defect. There were 1,262 definite anophthalmia and microphthalmia patients identified in the TBDR, with an overall combined prevalence of 3.0 per 10,000 live births. More than half (55.7%) of the patients had at least one chromosome abnormality or syndrome. In addition, 92.4% of nonsyndromic patients (i.e., have no recorded chromosome abnormalities or syndromes) had at least one additional birth defect. After adjustment for multiple factors, the prevalence of nonsyndromic anophthalmia and microphthalmia was higher among mothers who had ≥2 previous fetal deaths (PR = 1.43, 95% confidence interval [CI]: 1.03-1.97) and among mothers with any reported diabetes (PR = 2.08, 95% CI: 1.49-2.90). Our results confirm that children with anophthalmia and microphthalmia frequently have genetic syndromes or are born with other major birth defects. Our findings add to the limited body of literature on anophthalmia and microphthalmia as well as help define subgroups of women who are more likely to have children with this malformation.

    View details for PubMedID 30070760

  • Residential agricultural pesticide exposures and risks of preeclampsia. Environmental research Shaw, G. M., Yang, W., Roberts, E. M., Aghaeepour, N., Mayo, J. A., Weber, K. A., Maric, I., Carmichael, S. L., Winn, V. D., Stevenson, D. K., English, P. B. 2018; 164: 546–55


    We investigated risks of preeclampsia phenotypes from potential residential pesticide exposures, including 543 individual chemicals and 69 physicochemical groupings that were applied in the San Joaquin Valley of California during the study period, 1998-2011. The study population was derived from birth certificate data linked with Office of Statewide Health Planning and Development maternal and infant hospital discharge data. The following numbers of women with preeclampsia phenotypes were identified: 1045 with superimposed (pre-existing hypertension with preeclampsia) preeclampsia (265 with gestational weeks 20-31 and 780 with gestational weeks 32-36); 3471 with severe preeclampsia (824 with gestational weeks 20-31 and 2647 with gestational weeks 32-36); and 2780 with mild preeclampsia (207 with gestational weeks 20-31 and 2573 with gestational weeks 32-36). The reference population for these groups was 197,461 women who did not have diabetes (gestational or pre-existing), did not have any hypertensive disorder, and who delivered at 37 weeks or later. The frequency of any exposure was lower or about the same in each preeclampsia case group (further delineated by gestational age), and month time period, relative to the frequency in reference population controls. Nearly all odds ratios were below 1.0 for these any vs no exposure comparisons. This study showed a general lack of increased risks between a range of agriculture pesticide exposures near women's residences and various preeclampsia phenotypes.

    View details for PubMedID 29614386

  • Nutrient intake in women before conception and risks of anophthalmia and microphthalmia in their offspring. Birth defects research Weber, K. A., Yang, W., Carmichael, S. L., Shaw, G. M., National Birth Defects Prevention Study 2018; 110 (10): 863–70


    BACKGROUND: We previously explored associations between nutrients including folate and other macro and micronutrients and risks of anophthalmia or microphthalmia in the National Birth Defects Prevention Study. In the current study, we expand those previous results with larger sample sizes and conduct analyses with an additional diet quality index using more recent data.METHODS: The National Birth Defects Prevention Study is a population-based, multicenter case-control study of over 30 major birth defects, with estimated due dates from October 1997 to December 2011. Cases were 224 infants diagnosed with anophthalmia or microphthalmia. Controls were 11,109 live-born, nonmalformed infants randomly selected by each study center. Mothers completed a standardized, computer-assisted telephone interview between 6 weeks and 24 months after delivery. Mothers responded to a shortened food frequency questionnaire, assessing their nutrient intake for the year before pregnancy, and questions about periconceptional (2 months before to 2 months after conception) vitamin supplement use. Nutrient intake quartiles were based on the intake among controls.RESULTS: Among vitamin supplement users, odds of anophthalmia/microphthalmia were decreased for women with intake levels in the highest quartile of folate (0.56, 95% confidence interval [CI] 0.32-0.98), magnesium (0.42, 95% CI 0.22-0.82), and vitamin E (0.50, 95% CI 0.29-0.89). Among women not reporting vitamin supplement use, the odds were significantly increased for beta-carotene (2.5, 95% CI 1.10-5.68) and decreased for retinol (0.37, 95% CI 0.19-0.73).CONCLUSIONS: In this expanded analysis, we observed associations for a few nutrients, specifically forms of vitamin A. However, the heterogeneity of results by form and vitamin use necessitates further inquiry.

    View details for PubMedID 29504274

  • Occurrence of Selected Structural Birth Defects Among Women With Preeclampsia and Other Hypertensive Disorders AMERICAN JOURNAL OF EPIDEMIOLOGY Weber, K. A., Mayo, J. A., Carmichael, S. L., Stevenson, D. K., Winn, V. D., Shaw, G. M. 2018; 187 (4): 668–76


    To explore a potential association between preeclampsia and selected birth defects, we examined the prevalence of certain birth defects among women with hypertensive disorders including preeclampsia. We analyzed data from 2,499,536 singleton live births in California from 2007 to 2011, including maternal and infant demographics from birth certificates as well as clinical details from delivery hospitalization records. We examined defect groups that were recognizable at birth (e.g., spina bifida and cleft lip). Hypertensive disorders included preexisting hypertension, gestational hypertension, mild preeclampsia, severe preeclampsia/eclampsia, and preeclampsia superimposed on preexisting hypertension. Relative risk values with 95% confidence intervals for each birth defect were calculated by hypertensive group, as well as independent and joint associations of hypertensive and diabetic disorders. Risks of each type of birth defect were higher among offspring of women with hypertensive disorders compared with those without. The risks of birth defects among offspring of women with only a hypertensive disorder were significantly higher than that among women with neither hypertensive nor diabetic disorders (relative risks ranged from 1.37 to 2.77). Risks of birth defects were highest among those born to women with both hypertensive and diabetic disorders compared with those with neither (relative risks ranged from 1.80 to 6.22). These findings support the existence of an association between preeclampsia and certain birth defects and suggest that diabetes may be a contributing factor.

    View details for PubMedID 29020134

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