Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents

Key Points Question What are the trends, determinants, and association with small-for-gestational-age (SGA) birth of e-cigarette use among pregnant adolescents? Findings This cohort study using 2016-2021 data on 10 428 adolescents from the Pregnancy Risk Assessment Monitoring System in the US found that pregnant adolescents have increasingly used e-cigarettes, with the highest use among White adolescents. Adolescent use of cigarettes during pregnancy was a risk factor for SGA birth; however, adolescent use of e-cigarettes or dual use of e-cigarettes and cigarettes was not associated with SGA birth. Meaning This study suggests that e-cigarette use during late pregnancy among adolescents was not statistically significantly associated with a high risk of SGA birth.


Introduction
Cigarette smoking sometimes occurs among pregnant adolescents; 4.5% of people who gave birth in the US in 2021 smoked cigarettes during pregnancy, with the highest prevalence among young adults aged 20 to 24 years (5.8%) or 25 to 29 years (5.1%), followed by adolescents aged 15 to 19 years (4.3%). 1 E-cigarettes are another major tobacco or nicotine product used by US adolescents. 2,3cording to the 2022 National Youth Tobacco Survey, 3.3% of middle school students and 14.1% of high school students used e-cigarettes that year, 2 although it is unclear how common e-cigarette use is among pregnant adolescents.
Nicotine, carbon monoxide, and other chemicals in combustible cigarettes may contribute to the maternal smoking-related risk to the fetus. 4,5E-cigarettes are noncombustible and do not generate some of the toxic chemicals present in tobacco smoke, including carbon monoxide. 6For this reason, some pregnant people who smoke cigarettes before pregnancy use e-cigarettes as a smoking cessation aid to reduce nicotine intake and/or to reduce harm to the fetus. 7However, average nicotine delivery from e-cigarettes is comparable to that of combustible cigarettes. 8In addition, despite being 1 to 2 orders of magnitude lower than levels from combustible cigarette products, trace levels of certain toxicants, including formaldehyde, acetaldehyde, nickel, and lead, are present in e-cigarettes. 9The presence of those toxicants in emissions from e-cigarettes may explain, at least in part, why e-cigarette use during pregnancy is associated with adverse birth outcomes, such as low birth weight, preterm birth, and small-for-gestational-age (SGA) birth among people who gave birth, including adolescents and adults 10 and adults aged 18 years or older. 113][14][15] Between 2012 and 2016, the prevalence of SGA birth was as high as 12.1% in the US. 16SGA infants are at an increased risk for adverse health outcomes, including postnatal growth failure, 17 neurodevelopmental impairment, 18 short stature, 19 and type 2 diabetes. 20e study showed that infants of adolescents who smoked were 3.1 times more likely to be SGA compared with infants of adolescents who did not smoke cigarettes. 21Compared with adults who have given birth, adolescents may be more vulnerable to smoking-related health risks due to the biological and psychosocial factors pertaining to adolescent pregnancies.One prior study showed that infants of adolescents (aged 12-18 years) who smoked during pregnancy had a greater reduction in birth weight than infants of adults who smoked during pregnancy (−202 g vs −158 g per pack per day). 22Despite existing findings on the adverse health effects of cigarette smoking among pregnant adolescents, little is known about e-cigarette use among this population with increased health vulnerability.
Therefore, using a large US national pregnancy monitoring system, we aimed to fill the aforementioned research gaps by examining exclusive e-cigarette use, exclusive cigarette use, and dual use of e-cigarettes and cigarettes during pregnancy among adolescents.We focused on yearly trends in use from 2016 to 2021, sociodemographic and pregnancy-related determinants, and a potential health outcome of pregnancy (SGA birth).

Population and Sample
In this cohort study, we conducted a secondary data analysis using Phase 8 of the US Pregnancy Risk Assessment Monitoring System (PRAMS; 2016-2021).The PRAMS is an ongoing state-level, population-based surveillance system first administered in 1987. 23It applies a mixed-mode approach of birth certificates, mailed surveys, and telephone surveys to collect information on maternal behaviors, attitudes, and experiences before, during, and shortly after (2-6 months) pregnancy.This information is all collected retrospectively after live birth and documentation of SGA status is available.Approximately 83% of all US births are covered by the PRAMS, including 47 states, the

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Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents District of Columbia, New York City, Puerto Rico, and the Great Plains Tribal Chairman's Health Board. 23The deidentified PRAMS data were provided by the Centers for Disease Control and Prevention.This secondary data analysis was approved as non-human participants research by the University at Buffalo institutional review board and did not require informed consent from study participants.This report followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
The total sample size of the Phase 8 PRAMS from 2016 to 2021 was 242 573 (eFigure in Supplement 1).First, given the significantly distinct developmental and health outcomes associated with multiple births, we excluded these data and focused solely on singleton births.Then we applied the age criterion for adolescence (10-19 years) defined by the World Health Organization. 24,25Among these adolescents, we included only those with complete data on e-cigarette and cigarette use during the last 3 months of pregnancy (late pregnancy).Furthermore, we restricted the analytic sample to adolescents who had complete data on SGA birth.

Exposure Measures
For e-cigarette use during late pregnancy, participants were asked the following question, "During the last 3 months of your pregnancy, on average, how often did you use e-cigarettes or other electronic nicotine products?"with response options of (1) more than once a day, (2) once a day, (3) 2 to 6 days a week, (4) 1 day a week or less, and (5) did not use e-cigarettes or other electronic nicotine products then.The questionnaire included a note that defined e-cigarettes as follows: "E-cigarettes (electronic cigarettes) and other electronic nicotine vaping products (such as vape pens, e-hookahs, hookah pens, e-cigars, e-pipes) are battery-powered devices that use nicotine liquid rather than tobacco leaves, and produce vapor instead of smoke."We dichotomized responses into e-cigarette use (options 1, 2, 3, or 4) or nonuse (option 5) during late pregnancy to ensure sufficient statistical power for further analyses on determinants of e-cigarette use as well as its association with SGA birth.For cigarette use during late pregnancy, participants were asked the following question, "In the last 3 months of your pregnancy, how many cigarettes did you smoke on an average day?" with response options of (1) 41 cigarettes or more, (2) 21 to 40 cigarettes, (3) 11 to 20 cigarettes, (4) 6 to 10 cigarettes, (5) 1 to 5 cigarettes, (6) less than 1 cigarette, and (7) did not smoke then.Similar to e-cigarette use, we dichotomized responses into cigarette use (options 1-6) or nonuse (option 7) during late pregnancy for further analyses.
Based on e-cigarette and cigarette use status during late pregnancy, we further categorized participants into 4 mutually exclusive groups: adolescents who did not use either e-cigarettes or cigarettes, those who exclusively used e-cigarettes, those who exclusively used cigarettes, and those who used both e-cigarettes and cigarettes (dual use).

Outcome Measures
Using data from birth certificates, the percentiles of birth weight by sex and gestational duration were calculated using the natality files for singleton births from the National Center for Health Statistics. 26We defined SGA birth as birth weight below the 10th percentile for the same sex and gestational duration, according to the cutoff point proposed by the World Health Organization. 27,28is definition of SGA has been applied in previous research using the PRAMS data. 29

Potential Determinants of E-Cigarette Use and Confounders
Based on the relevant literature, [30][31][32][33] we considered the following sociodemographic and pregnancyrelated characteristics as potential determinants of e-cigarette use during late pregnancy: age (10-17 years and 18 or 19 years), race (American Indian or Alaska Native, Asian or other race [no further information was provided for the category of "other race"], Black, multiracial, White), ethnicity (Hispanic or non-Hispanic), marital status (unmarried or married), type of health insurance (Medicaid, private insurance, self-pay, or other), prepregnancy hypertension (yes or no), prepregnancy diabetes (yes or no), prepregnancy body mass index (BMI; calculated as weight in

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Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents kilograms divided by height in meters squared), and the child's birth year (2016-2021).[36][37] Race and ethnicity were included due to known disparities in the prevalence of nicotine product use 30,33 and adverse birth outcomes. 37,38Race and ethnicity were obtained from birth certificates.
Due to small sample sizes, we combined the American Indian and Alaska Native categories into a single category.Similarly, the Asian and other race categories were combined into a separate single category.Additional information on selection of potential determinants can be found in the eMethods in Supplement 1.

Statistical Analysis
Information on the descriptive analysis can be found in the eMethods in Supplement 1.We used logistic regression models to examine whether the prevalence of e-cigarette and/or cigarette use significantly varied between 2016 and 2021.We used χ 2 tests for categorical variables (eg, race) and a linear regression model for BMI, a continuous variable, to identify significant sociodemographic and pregnancy-related determinants of e-cigarette and/or cigarette use.Similarly, χ 2 tests were used to compare the risk of SGA birth by categorical sociodemographic and pregnancy-related characteristics.For prepregnancy BMI (continuous), we compared its mean between SGA birth and non-SGA births using a linear regression model.We also used χ 2 tests to compare the risk of SGA birth across the 4 tobacco use groups.Then, we fitted multivariable binary logistic regression models to estimate the associations between e-cigarette and/or cigarette use with the risk of SGA birth.We calculated crude odds ratios (ORs) and confounder-adjusted ORs (AORs) and 95% CIs of SGA birth for adolescents who exclusively used e-cigarettes, exclusively used cigarettes, or used both cigarettes and e-cigarettes compared with adolescents who did not use either product (reference group).[32][33][34][35][36][37] To study the possible effect modification of prepregnancy BMI or the child's birth year in the association of e-cigarette and/or cigarette use with the risk of SGA birth, we added interaction terms between prepregnancy BMI or the child's birth year and e-cigarette or cigarette use to subsequent regression models.We focused on these 2 potential effect modifiers because previous research showed that the magnitude of the association between cigarette smoking during pregnancy and risk of SGA birth among pregnant adolescents who were underweight or normal weight was more striking than among those who were overweight or obese 39 and because e-cigarette devices have substantially changed through the recent years and thus the potential association of maternal use of e-cigarette products during pregnancy with fetal growth may have been changing with the child's birth year as well.In a sensitivity analysis to evaluate the robustness of our analytic results, we additionally excluded 36 adolescents (0.4%) who initiated the use of e-cigarettes (n = 25) or cigarettes (n = 11) during pregnancy so that the results could be interpreted as continuous use during pregnancy.
All data analyses were performed using SAS, version 9.4 (SAS Institute Inc).We defined statistical significance as 2-sided P < .05.Sampling weights were used in the statistical analysis to reduce potential selection bias due to nonrandom sampling, noncoverage, and nonresponse. 23

Sample Characteristics
In the original PRAMS sample of 242 573 births, 229 176 were singletons (eFigure in Supplement 1).Among these singletons, 10 746 were birthed by adolescents aged 10 to 19 years.Among these

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Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents adolescents, 10 451 had complete data on e-cigarette and cigarette use during late pregnancy and 10 428 of these had complete data on SGA birth (the final analytic sample).Table 1 shows the sociodemographic and pregnancy-related characteristics of the 10 428 pregnant adolescents in the analytic sample.Among them, 27.3% were aged 10 to 17 years and 72.7% were aged 18 or 19 years, a Sum of categories may not be equal to the total due to missing data.
b No additional information was provided about the races included in the "other race" category.

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Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents 58.9% self-identified as White and 23.3% as Black, 69.8% were non-Hispanic, 91.6% were unmarried, and 78.5% had Medicaid insurance.The children's birth years were evenly distributed from 2016 to 2021, with approximately 17% of the sample occurring each year.

Prevalence of E-Cigarette and/or Cigarette Use During Late Pregnancy
As shown in Table 2, 1.5% of the total sample exclusively used e-cigarettes, 7.3% exclusively used cigarettes, 1.2% used cigarettes and e-cigarettes, and the remaining 90.1% did not use either product during late pregnancy.Among those who reported exclusive e-cigarette use, 34.9% used e-cigarettes 1 day per week or less and 29.9% used e-cigarettes more than once a day (Table 1).Among those who The prevalence of dual use of cigarettes and e-cigarettes varied across the years, with a range from 0.6% to 1.6% (P = .38for the trend test).There were no significant pairwise comparisons for dual use between any 2 years.

Associations Between E-Cigarette and/or Cigarette Use During Late Pregnancy and SGA
In the total sample, 13.9% of children were born SGA ( Prepregnancy BMI was inversely associated with the risk of SGA birth, with a higher BMI associated with a lower risk of SGA birth (AOR, 0.96 [95% CI 0.94-0.98]per kg/m 2 increment) (Table 4).However, prepregnancy BMI did not modify the associations between e-cigarette and/or cigarette use and SGA.Similarly, the child's birth year was not a significant effect modifier.Finally, results did not change meaningfully in our sensitivity analysis by excluding the 36 adolescents who initiated the use of e-cigarettes or cigarettes during pregnancy.

Discussion
We found that the prevalence of e-cigarette use among US pregnant adolescents increased steadily from 2016 to 2021.This trend paralleled the increasing prevalence of e-cigarette use among all adolescents across similar years. 40,41Our finding that White adolescents were more likely than other racial groups to use e-cigarettes and cigarettes during late pregnancy was consistent with previous research in the general adolescent population. 42Another risk factor for cigarette use and dual use in our study sample was having Medicaid insurance (an indicator of low household income).This finding adds to the existing evidence on the high prevalence of smoking among adolescents with low socioeconomic status. 43In addition, we found that married adolescents were less likely than unmarried adolescents to exclusively use cigarettes or use both cigarettes and e-cigarettes, which was supported by the literature showing that being married was a protective factor against cigarette use and dual use during pregnancy among adults. 11 found that the risk of SGA birth was more than 2-fold higher among adolescents who exclusively used cigarettes during late pregnancy than those who did not.This finding was consistent with previous research showing that maternal cigarette use during pregnancy was a risk factor for SGA birth. 44Nicotine, carbon monoxide, other harmful chemicals in cigarettes may contribute to this association. 4For instance, carbon monoxide, which is present in cigarettes but not in most e-cigarettes, can cause fetal hypoxia and thus lead to fetal growth restriction. 5novel finding from our analysis was the statistically nonsignificant association between adolescent e-cigarette use during late pregnancy and the risk of SGA birth.This finding might be associated with the fact that e-cigarettes contain little carbon monoxide and potentially lower nicotine concentrations compared with cigarettes.Cigarettes produce 0.8 to 1.7 mg of carbon monoxide and 81.5 to 187.7 μg of nicotine per puff.[45][46][47][48] However, e-cigarettes usually do not produce carbon monoxide above the limit of detection, 49 and the estimated amount of nicotine is 0 to 52 mg/mL.50 Still, previous studies indicated that e-cigarette use during pregnancy may be a risk factor for SGA birth among adults (aged Ն18 years) 51 and among adolescents and adults.29 For example, Cardenas et al 51 found that adult mothers who used e-cigarettes during pregnancy had a several times higher risk of SGA birth than mothers who did not use e-cigarettes.The reasons for the seeming inconsistency with our observed nonsignificant association among adolescents are unknown, but there are several plausible explanations.First, adolescents may have a shorter duration and a lower cumulative amount of e-cigarette use than older adults.It has been reported that most US adolescents begin using e-cigarettes in middle school and high school, [52][53][54] so it is possible that the adolescents in our sample had not been using e-cigarettes for very long.As a result, their exposure to e-cigarettes might influence them and their offspring less, compared with adults.
Second, our statistical power might have been insufficient to detect significant associations due to the relatively small number of adolescents in the PRAMS sample who exclusively used e-cigarettes or used both e-cigarettes and cigarettes.

Limitations
This study has some limitations.First, self-reported e-cigarette and cigarette use measures were subject to recall bias, and the prevalence might have gone underreported due to social stigma, especially given that respondents completed the surveys retrospectively during the 2-to 6-month postpartum period.Second, the sample sizes for adolescents who used e-cigarettes (n = 152 [1.5%, weighted]) or both e-cigarettes and cigarettes (n = 125 [1.2%, weighted]) during pregnancy were relatively small, which might widen the 95% CIs in our estimated risk of SGA birth among them; therefore, caution is needed to interpret those results.Third, information on e-cigarette and cigarette use during the first and second trimesters of pregnancy was not available in the PRAMS; thus, we could not examine the potential association of the timing of exposure during pregnancy with SGA births. 55,56This limitation also did not allow us to distinguish individuals who used e-cigarettes and/or cigarettes throughout pregnancy from individuals who used these products only

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Use of E-Cigarettes and Cigarettes During Late Pregnancy Among Adolescents during the third trimester.Fourth, there was a lack of information on secondhand smoke exposure during pregnancy, which also could have a negative association with fetal growth and might have been an unmeasured confounder. 57Fifth, information on specific e-cigarette devices used by the participants was not available in the PRAMS.Given the changes in the tobacco product market, it could be difficult to draw conclusions on specific products over time.Sixth, we did not control for use of other substances, such as cannabis, due to a large amount of missing data.Thus, we could not distinguish whether individuals used electronic delivery devices to vape nicotine, cannabis, or both substances.Use of all these products can occur among adolescents 58 and potentially have different associations with fetal growth. 59This limitation is particularly important in interpreting the results for individuals who use both nicotine and cannabis.Our estimated OR for cigarette use might be overestimated, given the reported associations of cannabis use with SGA and low birth weight. 60,61venth, we dichotomized e-cigarette and cigarette use (use vs nonuse) due to limited sample sizes of the original frequency categories.This simplified approach created a heterogeneous use group with considerable variability in use frequency and did not allow us to examine the potential doseresponse association with risk of SGA birth.Eighth, maternal diet quality could have a substantial association with fetal growth, 62,63 but it was not considered in our analysis due to lack of information.

Conclusions
In this cohort study of US pregnant adolescents, there was an increase in e-cigarette use and a decrease in cigarette use during late pregnancy from 2016 to 2021.In this population with a potentially higher risk of SGA birth, exclusive cigarette use was a risk factor for SGA birth.Exclusive e-cigarette use and dual use of cigarettes and e-cigarettes did not seem to be statistically significantly associated with SGA birth in our analysis, but this finding should be interpreted with caution given the low prevalence of use and the limited sample size.Considering the uncertainty of this nonsignificant association, future research using a larger sample size may be beneficial.

Table 2 .
Determinants of EC and/or CC Use During Late Pregnancy Among Adolescents, and Their Risk of Small-for-Gestational-Age Birth Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); CC, combustible cigarette; EC, e-cigarette; NA, not applicable.aCalculatedfromχ 2 tests for categorical determinants or from a linear regression model for the continuous determinant (prepregnancy BMI).Statistical significance was defined as a 2-sided P < .05.bNo additional information was provided about the races included in the "other race" category.cThemean (SE) prepregnancy BMI for adolescents with non-SGA birth was 25.2 (0.1).

Table 2
). White adolescents had the highest prevalence of exclusive e-cigarette use (2.7%) and exclusive cigarette use (9.8%), whereas Black adolescents had the lowest prevalence of exclusive e-cigarette use (0.6%) and Asian or other race adolescents had the lowest prevalence of exclusive cigarette use (1.2%).Compared with Hispanic adolescents, non-Hispanic adolescents had a higher prevalence of exclusive e-cigarette use (2.2% vs 1.1%), exclusive cigarette use (8.9% vs 1.9%), and dual use (1.6% vs 0.2%).Compared with unmarried adolescents, married adolescents were less likely to exclusively use e-cigarettes (1.4% vs 1.9%) or cigarettes (6.3% vs 6.8%).Adolescents with Medicaid insurance were more likely than adolescents with other health insurance to exclusively use cigarettes (7.1% vs 5.2%) and use both e-cigarettes and cigarettes (1.4% vs 0.6%).
). Being unmarried (14.0%vs 10.7% being married) and a lower prepregnancy BMI were significant risk factors for SGA.Compared with adolescents who did not use either product, those who exclusively used e-cigarettes appeared to have no significantly different odds of SGA birth (16.8% vs 12.9%; crude OR, 1.37 [95% CI, 0.73-2.56];AOR,1.68 [95% CI, 0.89-3.18])(Table3).Similarly, those who used both e-cigarettes and cigarettes appeared to have no significant difference in the odds of SGA birth from those who did not use either The trend test P values were P < .001for exclusive e-cigarette use from 2016 to 2021, P < .001for exclusive cigarette use from 2017 to 2021, and P = .38for dual use from 2016 to 2021.Error bars indicate 95% CIs.product

Table 3 .
Crude and Adjusted Associations Between EC and/or CC Use During Late Pregnancy and Small-for-Gestational-Age Birth Among Adolescents Abbreviations: CC, combustible cigarette; EC, e-cigarette; NA, not applicable; OR, odds ratio.aAdjusted for maternal age, race, ethnicity, marital status, health insurance, prepregnancy body mass index, prepregnancy diabetes, prepregnancy hypertension, and the child's birth year.

Table 4 .
Interactions Between Prepregnancy BMI or Child's Birth Year and EC and/or CC Use During Late Pregnancy in the Risk of Small-for-Gestational-Age Birth Among Adolescents a Adjusted for maternal age, race, ethnicity, marital status, health insurance, prepregnancy diabetes, prepregnancy hypertension, and the child's birth year.bPrepregnancy BMI was centered at 25.0.