Association Of Maternal Pyrethroid Insecticide Exposure During Pregnancy and Neonatal Birth Outcomes in the SAWASDEE Birth Cohort Study Open Access

Abstract

Background: Synthetic pyrethroids (PYRs) are ubiquitously used insecticides in agricultural and household settings, especially in low- and middle-income countries. Given the uncertainty around the human health implications of PYR exposure, understanding the effects among vulnerable populations such as pregnant people, children, and occupational workers is crucial. The Study of Asian Women and their Offspring’s Development and Environmental Exposures (SAWASDEE) was established between 2017 and 2019 in northern Thailand to understand the links between trimester-specific organophosphate and pyrethroid exposures and neurodevelopmental trajectories of children born to agricultural workers.

 

Objective: To elucidate the impact of trimester-specific and pregnancy average maternal PYR exposure, as assessed using urinary 3-phenoxybenzoic acid (3-PBA) levels, on neonatal birth weight.

 

Methods: Three PYR metabolites were measured in 333 participants’ composite urine samples collected from each trimester and over 6-8 visits. Trimester-specific surveys collected demographics, medical history, occupational and exposure scenario information; and birth records provided birth weight and health data. Associative multivariable linear regression models for each trimester and pregnancy average were built to ascertain the association.

 

Results: Mean neonatal birth weight was 2.98kg (SD = 0.42kg) and the geometric mean maternal urinary 3-PBA measurement was 0.475ng/mL (GSD = 1.870ng/mL) for mothers who were followed throughout pregnancy. Effects were differential based on trimester and location, sensitive to extreme exposure and outcome, and not statistically significant. Overall, in Chom Thong district, neonatal birth weight increased by 0.44g (95%CI –0.19g, 1.06g) for a 1% increase in 3-PBA (ng/mL) whereas in Fang district, it decreased by 0.021g (95%CI –1.652g, 1.611g). Regardless of location and effect directionality, 1% increase in maternal urinary 3-PBA during Trimester 1 may have a lesser impact on neonatal birth weight than that of Trimester 2 which appeared to be similar to that of Trimester 3.

 

Conclusion: Our results indicate a positive association between maternal PYR exposure and birth weight in Chom Thong district and a negative association in Fang during this study period. There may be differential impact based on exposure dose and duration. Future evaluations incorporating mixture analyses, specific PYR metabolites, and pregnancy periods are warranted.

Table of Contents

Introduction. 1

Methodology. 4

SAWASDEE Cohort. 4

Study Population. 4

Maternal Urine Collection and PYR Urinalysis. 5

Questionnaire & Case Records Data Collection. 7

Statistical Analysis for Birth Weight And PYR. 8

Results. 13

Study Population Characteristics. 13

PYR Exposure Measurements In The SAWASDEE Cohort. 14

Neonatal Birth Weight In The SAWASDEE Study. 17

Association Of Birth Weight And PYR Exposure. 18

Unadjusted Association of Birth Weight and Maternal Urinary 3-PBA. 18

Comparison Of Associative Models. 18

Results From Final Model. 20

Sensitivity Analysis. 23

Discussion. 28

Summary Of Findings And Comparison To Literature. 28

Study Strengths. 31

Study Limitations. 32

Future Recommendations. 34

Conclusion. 35

Conflict Of Interest. 35

References. 36

Appendix A: Quality Control For Exposure Analysis Methodology. 41

Appendix B: Descriptive Statistics And Model Summary Tables. 41

Appendix C: Summary Of Sensitivity Analyses With Pregnancy Average Period. 51

Appendix D: Comparison Of Effect Estimates Of PYR Metabolite On Birth Weight Reported In Literature. 56

About this Master's Thesis

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School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Environmental Health
Keyword	Thailand synthetic pyrethroids birth outcomes SAWASDEE Study pregnant people agricultural farm workers
Committee Chair / Thesis Advisor	Barr, Dana Boyd , Emory University

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