Adverse Birth Outcomes Associated With Prepregnancy and Prenatal Electronic Cigarette Use
E-cigarette solutions usually contain nicotine, flavourings and additives, of which some convert to known toxicants (eg. formaldehyde).
Previous animal studies showed that the offspring of mothers exposed to e-cigarettes were adversely affected with reduced birth weights, short-term memory loss, reduced anxiety, increased brain DNA methylation, oxidative stress and inflammation.
On the other hand, human studies so far have identified an increased risk of lung injury linked to vaping, with only a small number of studies on adverse birth outcomes carried out to date.
To assess the proportion of adults who used e-cigarettes before and during pregnancy and whether e-cigarette use during pregnancy, either exclusively or in combination with combustible cigarette smoking, was associated with an increased prevalence of adverse birth outcomes.
Data from the Pregnancy Risk Assessment Monitoring System (PRAMS) in the U.S. between 2016 to 2018, covering 37 states, was analysed for this study.
The PRAMS questionnaire is linked to birth certificates which includes information such as birth weight, gestational age, size, parity and any prenatal care.
Only women singleton pregnancies, with birth weights ≥ 400g, and information regarding e-cigarette use plus all potential covariates was included in this study.
Women were then classified into 3 main categories;
- E-cigarette use in the 3 months before pregnancy, but not in the last 3 months of pregnancy
- E-cigarette use in the last 3 months of pregnancy
- No e-cigarette use in the 3 months before pregnancy, or the last 3 months of pregnancy
E-cigarette users were also further classified according to combustible cigarette use;
- Both e-cigarette and combustible cigarette use, in the last 3 months of pregnancy
- Only e-cigarette use, in the last 3 months of pregnancy
The frequency of e-cigarette use before pregnancy, and during the last 3 months of pregnancy, was recorded as: once or more per day, less than once a day, and no use.
Adverse outcomes included preterm birth, low birth weight (LBW) and small-for-gestational age (SGA). Preterm birth was defined as a newborn child less than 37 weeks gestation, LBW less than 2,500g, while SGA is a birth weight in the lowest 10th percentile for gestational age.
A variety of covariates was defined including age, pre-pregnancy BMI, education, marital status, ethnicity, residence, parity, special supplemental nutrition pack, multivitamin use, prenatal care and obstetric risk factors (diabetes or gestational diabetes, hypertension or gestational hypertension, preeclampsia, previous preterm birth, infertility treatment, use of assisted reproductive technology and previous caesarean) to better interpret any findings.
A total of 79,176 respondents to the PRAMS questionnaire satisfied this study’s inclusion criteria.
Among the 79,176 respondents, 2.7% reported using e-cigarettes use in the 3 months before pregnancy, but not in the last 3 months of pregnancy, while 1.1% reported e-cigarette use in the last 3 months of pregnancy.
Of those women who used e-cigarettes in the last 3 months of pregnancy, 63.7% also smoked combustible cigarettes.
Initial analysis of participants characteristics revealed e-cigarette use was more likely in women: non-Hispanic white, aged 18-24 years, single, less than 16 years of education, living rural, with public health insurance, 2 or more prior births, with inadequate prenatal care, who accessed the special supplemental nutrition pack, and were combustible cigarette smokers.
Adverse outcomes analysis, revealed the overall rates for preterm, SGA and LBW was 7.6%, 9.7% and 6.1% respectively among all participants.
Comparing the prevalence of adverse outcomes between nonusers and e-cigarette users, in the 3 months before pregnancy only, revealed no statistically significant differences in this study.
However, comparing the prevalence of adverse outcomes between nonusers and e-cigarette users, in the last 3 months of pregnancy, revealed a significantly higher prevalence of LBW among e-cigarette users (adjusted prevalence ratio 1.33).
Next, comparing the prevalence of adverse outcomes between nonusers and e-cigarette users, who specifically did not smoke any combustible cigarettes, in the last 3 months of pregnancy, revealed a statistically higher prevalence of preterm birth (adjusted prevalence ratio 1.69) and LBW (adjusted prevalence ratio 1.88).
Interestingly this result was significantly greater than those who smoked combustible cigarettes together with e-cigarettes (adjusted prevalence ratio 1.10) compared to nonusers.
Next analysing the frequency of e-cigarette use, again between nonusers and daily e-cigarette users, who specifically did not smoke any combustible cigarettes, in the last 3 months of pregnancy, revealed an even higher prevalence of preterm birth (adjusted prevalence ratio 1.94) and LBW (adjusted prevalence ratio 2.00).
Not surprisingly, comparing nonusers to nondaily e-cigarette users, who specifically did not smoke any combustible cigarettes, in the last 3 months of pregnancy, reduced the risk of preterm birth (adjusted prevalence ratio 1.26) and LBW (adjusted prevalence ratio 1.76) mildly.
SUMMARY: VAPING WHILE PREGNANT
In this study, vaping daily while pregnant, particularly in the last 3 months of foetus development, increased the prevalence of adverse outcomes, essentially doubling the risk of preterm birth (adjusted prevalence ratio 1.94) and low birth weight (adjusted prevalence ratio 2.00).
- Other adverse events, different e-cigarette constituents and use during the first 6 months of pregnancy not collected by the PRAMS questionnaire.
- Total number of e-cigarette users limited the potential to detect smaller statistically significant differences between subgroups.
No external funding was declared for this study.
Variables, i.e. participant characteristics, that may affect the result.
The addition of a methyl group to a nucleotide base of your DNA.
Wang X, et al. (2020). Smoking and use of electronic cigarettes (vaping) in relation to preterm birth and small-for-gestational-age in a 2016 U.S. national sample. https://doi.org/10.1016/j.ypmed.2020.106041
Cardenas V M, et al. (2019). Use of electronic nicotine delivery systems (ENDS) by pregnant women I: risk of small-for-gestational-age birth. https://doi.org/10.18332/tid/106089
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