Original Article

Open Access: Mediation Analysis of Maternal Smoking, Gestational Age, and Birth Weight on the Texas–Mexico Border

Authors: Chinodebem Ogbutor, MA, Stephanie M. Mishaw, MD, MPH, Zuber D. Mulla, PhD

Abstract

Objectives: Published data on the indirect effect of maternal smoking on birth weight as mediated by gestational age in Hispanic populations are lacking. Our goal was to conduct such a mediation analysis using data from El Paso County, Texas.

Methods: El Paso County is located on the US−Mexico border. A simple mediation analysis was conducted using year 2010 El Paso County birth certificate data. The SAS macro PROCESS 3.5.3 was used to estimate the direct and indirect effects of active maternal smoking (by trimester) on birth weight (in grams) in the setting of linear regression. The single mediator was gestational age in weeks. A direct or indirect effect was deemed to be present if the 95% confidence limits (CLs) excluded 0. Analyses were adjusted for multiple variables, including maternal prepregnancy body mass index. The indirect effect was reported along with a 95% bootstrap CL.

Results: A total of 16,654 singleton births were included in the cohort. The majority of the mothers were White Hispanic (87.2%). The mean (standard deviation) birth weight was 3198.6 g (517.2). A direct effect of maternal smoking during each trimester on birth weight was detected. An indirect effect of maternal smoking on birth weight was not detected in any of the trimesters. In adjusted analyses for the third trimester, the indirect effect for every 1-U increase in the mean number of cigarettes smoked per day was −4.18 (95% bootstrap CL −10.64 to 1.99).

Conclusions: In our large, predominantly Hispanic cohort, it appears that gestational age is not a mediator of the effect of maternal smoking on birth weight. Future studies in our population should explore other possible mediators of this association.
Posted in: Pregnancy32 Family Planning & Reproductive Health14

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References

1. March of Dimes. Peristats. Quick facts: preterm birth. 2019. Available at: https://www.marchofdimes.org/peristats/reports/united-states/report-card. Accessed March 29, 2023.
 
2. March of Dimes. Peristats. Low birthweight: United States, 2009–2019. Available at: https://stacks.cdc.gov/view/cdc/100472https://stacks.cdc.gov/view/cdc/100472. Accessed March 29, 2023.
 
3. Azagba S, Manzione L, Shan L, et al. Trends in smoking during pregnancy by socioeconomic characteristics in the United States, 2010–2017. BMC Pregnancy Childbirth 2020;20:52.
 
4. Soneji S, Beltrán-Sánchez H. Association of maternal cigarette smoking and smoking cessation with preterm birth. JAMA Netw Open 2019;2:e192514.
 
5. Perez da Silva Pereira P, Da Mata FAF, et al. Maternal active smoking during pregnancy and low birth weight in the Americas: a systematic review and meta-analysis. Nicotine Tob Res 2017;19:497–505.
 
6. Singleton EG, Harrell JP, Kelly LM. Racial differentials in the impact of maternal cigarette smoking during pregnancy on fetal development and mortality: concerns for black psychologists. J Black Psychol 1986;12:71–83.
 
7. US Census Bureau. QuickFacts. El Paso County, Texas. https://www.census.gov/quickfacts/elpasocountytexas. Accessed May 22, 2021.
 
8. Hayes AF. Introduction to Mediation, Moderation, and Conditional Process Analysis, Second Edition: A Regression-Based Approach. New York: The Guilford Press; 2018.
 
9. Bandoli G, Palmsten K, Flores KF, et al. Constructing causal diagrams for common perinatal outcomes: benefits, limitations and motivating examples with maternal antidepressant use in pregnancy. Paediatr Perinat Epidemiol 2016;30:521–528.
 
10. Northam S, Polancich S, Restrepo E. Birth certificate methods in five hospitals. Public Health Nurs 2003;20:318–327.
 
11. Texas Department of State Health Services. Birth registrars. https://www.dshs.texas.gov/vital-statistics/vital-statistics-partners/birth-registrars?terms=birth%20registrar%20training. Accessed April 5, 2022.
 
12. Grant A, Morgan M, Gallagher D, et al. Smoking during pregnancy, stigma and secrets: visual methods exploration in the UK. Women Birth 2020;33:70–76.
 
13. Vartiainen E, Seppälä T, Lillsunde P, et al. Validation of self reported smoking by serum cotinine measurement in a community-based study. J Epidemiol Community Health 2002;56:167–170.
 
14. Kim S. Overview of cotinine cutoff values for smoking status classification. Int J Environ Res Public Health 2016;13:1236.
 
15. Jung SJ. Introduction to mediation analysis and examples of its application to real-world data. J Prev Med Public Health 2021;54:166–172.