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. Author manuscript; available in PMC: 2022 Sep 1.
Published in final edited form as: Curr Addict Rep. 2021 Jul 13;8(3):347–365. doi: 10.1007/s40429-021-00380-w

TABLE 1.

ENDS USE & TRANSITIONS IN ENDS USE DURING PREGNANCY

Citation, Dataset, and Sample Pregnancy Groups and/or Timepoints ENDS and other TP Use Groups and/or Timepoints Summary of Findings Relevant to ENDS and/or Pregnancy: prevalence reported as %; odds ratios (OR) or adjusted OR (aOR) or relative risk (RR) always followed by [95% Confidence Intervals (CI)]
SECTION A. TRANSITIONS IN ENDS USE ACROSS PREGNANCY
Cardenas et al 2020 [61]
Dataset: PRAMS; Phase 8 of the Arkansas PRAMS (2016–2017)
Sample: Arkansan women who had a live singleton birth during the Phase 8 cycle time frame and had complete information on TP use and SGA (N=1,594)
Location: United States (Arkansas)		 Examined use/change in use for tobacco products during:

  1. Pre-pregnancy: 3mo before pregnancy

  2. Late pregnancy: Last 3mo of pregnancy

 TP Use Groups based on Pre-pregnancy and/or Late pregnancy timepoints:

  1. CC Only (n=372):

  2. ENDS Only (n=18)

  3. Dual Uses (n=100)

  4. Other TP Only (n=42): other=hookah, tobacco chew, snuff, snus, dip, cigars, cigarillos, or little filtered cigars

  5. No TP Use (n=1,062)


Considered to be ENDS user if reported ENDS use “one day a week or less” or “more than once a day”.		 Among Those With Dual Use At Pre and/or Late Pregnancy:

  1. 13% did not use ENDS at pre-pregnancy

  2. 54% stopped using ENDS at pre-pregnancy or late pregnancy.

Among Those With Dual Use at Pre-pregnancy:

  1. 44.8% reduced the number of CCs they smoked;

  2. 5% stopped smoking CCS (but continued using ENDS);

  3. 24.1% stopped all TP use.

Among subjects who started using ENDS during pregnancy: 85.4% decreased the number of CCs they smoked; but none completely stopped CC smoking by late pregnancy. No participants switched from CC only at pre-pregnancy to ENDS only use at late pregnancy.
Chiang et al 2019 [57]
Dataset: Quit4baby Trial, within individuals enrolled in Text4baby text service (2015–2016)
Sample: Pregnant women; age 14 or older; smoked at least 1 puff of a cigarette in the 2-weeks prior to enrollment, completed a follow-up and were still pregnant at follow-up (N=428); enrolled in text service for pregnant women “Text4Baby”.
Location: United States (national sample)		 All participants were currently pregnant at the time of enrollment.

Sample limited to women who completed a 1-month follow up assessment, and were still currently pregnant at follow-up.		 Primary focus of the trial was to measure CC cessation in those randomized to continue Text4baby standard text messages vs. a Text4baby plus Quit4baby text message system. Separate prior paper reporting on main RCT results reported limited efficacy of the intervention for CC smoking (Abroms et al. 2017)). Focus of this secondary analysis paper is to consider ENDS use as the main exposure variable of interest. Analyses run with and without Quit4baby treatment group allocation in the model: did not affect ENDS use transitions.

ENDS Use transition groups based on reports of any ENDS use in past 7 days, measured at baseline (T1) and at 1-month follow-up assessment (T2). CC quit status at T2 defined as no use in past 7 days at T2 (i.e., 7 day point prevalence abstinence).		 Prevalence ENDS Use: 8.4% T1, 7.0% T2.
Stopped ENDS: Among those using ENDS at T1, 55.56% did not use ENDS at T2.
Started ENDS: Among those not using ENDS at T1, 3.57% at T2.
CC Quit Rate per ENDS Trajectory Group: Continued using ENDS: 12.50% (2/16) Stopped using ENDS: 25.0% (5/20) Started using ENDS: 7.14% (1/14). Continued Not Using ENDS: 26.4% (99/375)

Top reason cited for ENDS use was to help quit smoking CC. But odds quitting CC were non-significantly lower among ENDS use vs. non-ENDS use groups (OR= 0.70 (0.30, 1.64)).
Kapaya et al 2019 [50]
Dataset: PRAMS; Oklahoma and Texas PRAMS datasets (2015)
Sample: Population-based (stratified, random) sample of women with a recent live birth (surveyed 2–6 months post-delivery); identified by birth certificate records (N=3,277)
Location: United States (Oklahoma and Texas)		 Retrospective self-report of ENDS use during following time frames:

  1. Before pregnancy: >3 months before pregnancy

  2. Around the time of pregnancy: any time during the 3 months before pregnancy, the last 3 months of pregnancy, or 2–6 months after delivery

 Any ENDS Use during specific time periods:

  1. >3 months before pregnancy (n=459; 10.4%)

  2. Around the time of pregnancy (n=285; 7.0%)

  3. During 3 months before pregnancy (n=223; 5.8%)

  4. During last 3 months of pregnancy (n=70; 1.4%)

  5. 2–6 months after delivery (n=96; 2.1%)

  6. None (n=2,533; 82.6%)


Also assessed ENDS use within those who smoked CC within past 2 years (Past CC) vs. those who did not smoke CC within past 2 years (No Past CC).		 Among those who used ENDS during last 3 months of pregnancy, 38.4% used ENDS containing nicotine, 35.2% used ENDS that did not contain nicotine, and 26.4% reported not knowing if the ENDS they used contained nicotine.

ENDS Use within Past CC vs. No Past CC: Higher rates ENDS in Past CC vs. No Past CC at >3 mo before pregnancy (29.8% vs 6.0%) and around the time of pregnancy (25.1% vs 2.9%).

Among Past CC who ever used ENDS, prevalence of Dual use was 38.0% at >3mo before pregnancy, 7.7% during last 3 mo pregnancy, 11.8% at 2–6mo after delivery; ENDS only use highest in 2–6 months after delivery (3.8%); no TP use highest during the last 3 months of pregnancy(61.9%).

Top reported reasons for ENDS use among women using ENDS >3mo & those who used ENDS around the time of pregnancy: 1) curiosity (78.6%, 54.0%), 2) perception ENDS help with quitting or reducing CC (27.4%, 45.2%); 3) perception ENDS less harmful than CC (24.6%, 45.2%); 4) availability of flavors (24.5%, 42.3%); 5) ability to get ENDS without nicotine (16.9%, 41.4%).
Kim 2020 [45]
Dataset: PATH; Waves 1–4 (2013–2017)
Sample: Adult women (age 18+) with complete data from any 2 consecutive Waves (T1 and T2); who were pregnant at T2, but NOT pregnant at T1 (N=864)
Location: United States (nationally representative sample)		 Examined TP use in participants at 2 timepoints during pregnancy (T1 and T2):

  1. Pre-Pregnancy: Wave prior to current pregnancy (T1)

  2. Pregnancy: Wave of current pregnancy (T2).


Data was not time-locked with specific gestational period, but information on gestational trimester was collected.		 TP use definition: Ever used (product category) regularly, and currently using it every day or some days.

Compared factors differing between those who quit all TP (n=162) vs. persistent ENDS users (n=29) or persistent CC users (n=159) at T2.		 Rates of ENDS use decreased from pre-pregnancy (6.1%) to pregnancy (2.8%).

ENDS cessation rate (T1 vs. T2) = 76.2%

Complete TP abstainers vs. persistent ENDS users did not differ in pregnancy trimester at time of T2 survey [persistent ENDS users 25.9% first, 42.0% second, 32.1% third trimester].

Persistent ENDS users (vs. complete TP quitters): more likely to be White, have non-private or no medical insurance.
Kurti et al 2017 [49]
Dataset: PATH Wave 1 (2013–2014)
Sample: Women (aged ≥18) who reported being pregnant at the time of survey completion (N=388)
Location: United States (nationally representative sample)		 Analyses included currently pregnant persons.

Survey was not time-locked with specific gestational age. Average gestational age at time of data collection was 21 weeks.		 ENDS and CC use classified as Current, Former, or Never Users.

Current ENDS use=using some days or every day (either established (EST) or experimental (EXP) use); Former ENDS use= previously using some days or every day (EST or EXP) and no current use; Never use = no lifetime use.
CC use categories: same definitions as ENDS but required 100+ CC in lifetime to count as a current or former CC smoker.		 Prevalence of Current ENDS use:
Among current CC smokers: 28.5%.
Among former CC smokers: 2.3%.
Among never CC smokers:0%
Among Current ENDS users, mean # of days of ENDS use in the past 30 days=13.1.

Odds of Current ENDS use significantly higher among current vs former CC smokers (aOR=28.02 (9.95–78.92)); and among those who did vs. did not use illicit drugs in the past year (aOR=3.84 (1.49–9.90).
Kurti et al 2018 [13]
Dataset: PATH; Waves 1–2 (2013–2015)
Sample: Adult women (18–44) who had complete data for Waves 1–2 and were NOT pregnant at Wave 1 (N=7,814)
Location: United States (nationally representative sample)		 Pregnancy groups defined by self-reported ‘currently pregnant’ (y/n) at T2 (none pregnant at T1):

  1. Pregnant (n=332)

  2. Not Pregnant (n=7,482)


Average gestational age of the sample at T2 was 20.7 weeks.		 Tobacco product use: Current established (EST) or experimental (EXP) use of CCs, ENDS, hookah, and any cigar (traditional cigars, filtered cigars, and cigarillos).
T1 ENDS Use
Pregnant: 5.2% (2.8% EST, 2.4% EXP) Not Pregnant: 6.2% (2.7% EST, 3.5% EXP)
No information on ENDS characteristics.
Definition of Quit tobacco product at T2: Current user at T1, former user of same product category at T2.		 Quit Rates for ENDS at T2:
Pregnant: 81.3% (71.2% of EST, 100.0% of EXP).
Not Pregnant: 45.0% (32.8% of EST, 55.1% of EXP).

Pregnancy was the strongest predictor of quitting ENDS (aOR=20.99(2.6, 170.3)). Results suggest this relationship may vary by ENDS use status (EST vs. EXP). Absence of pregnant EXP users at T2 (n=0) prevented the authors from calculating
ORs.
Kurti et al 2020 [44]
Dataset: Population Assessment of Tobacco and Health (PATH);
Waves 1–3 (2013–2016)
Sample: Adult women (18–49) who completed 2 consecutive waves of data (T1, T2); were not pregnant at T1; and used combustible TP at T1 (N=3,767)
Location: United States (nationally representative sample)		 Pregnancy groups defined by self-reported ‘currently pregnant’ (y/n) at T2 (none were pregnant at T1):

  1. Pregnant (n=197; 4.5%)

  2. Not Pregnant (n=3,570; 95.5%)


Pregnant at T2 was considered as predictor variable in analysis of tobacco transitions.

Average gestational age of the pregnant sample at T2 was 21.7 weeks.		 TP Use Transition Groups, Defined by T2 (all had Combustible TP Use at T1, none were pregnant at T1):

  1. T1 Combustible TP (cTP) Use → T2 cTP Use (“Harm Maintaining”*). Continued use of cTP (CC, hookah, pipes, cigars); with or without ENDS. n=3,156; 2.8% pregnant at T2)

  2. T1 cTP Use→ T2 ENDS Only (“Harm-Reducing”*) n=87; 1.2% of whom were pregnant at T2)

  3. T1 cTP Use→ T2 No TP Use (“Harm-Eliminating”*) n=524; 14.5% of whom were pregnant at T2)

*Harm labels from TP Use groups assigned in paper based on presumed risk; no adverse health outcomes measured in these groups.

ENDS use at T1 considered as prediction variable, but not considered in definition of transition groups.

ENDS Use defined as using regularly (“current established”) or at least some days (“experimental”).		 ENDS use Prevalence at T1
Overall (total sample) = 22.4%
T1 cTP Use → T2 cTP Use = 23.4%
T1 cTP Use→ T2 ENDS Only = 37.9%
T1 cTP Use→ T2 No TP Use = 14.6%

Predictors of TP Use Transition Groups
→T2 No Combustible TP Use (“Harm-Eliminating”)
Pregnancy at T2 increased odds (aOR=5.97 (3.92–9.10))
**ENDS use at T1 decreased odds (aOR=0.56 (0.42–0.76))

→ T2 ENDS Only (“Harm-Reducing”) Pregnancy at T2: not a significant predictor.
**ENDS use at T1 increased odds (aOR=1.92 (1.04–3.55))

**ENDS use at T1 predictor results includes pregnant and non-pregnant women in sample.
Schilling et al 2020 [46]
Dataset: STudy on E-cigarettes and Pregnancy (STEP)
Sample: Pregnant women, aged 17+, who registered for birth at a clinic (Asklepios Klinik Barmbek) between April 4th, 2018, and January 11th, 2019, provided informed consent and complete CC & ENDS data (N=540)
Location: Germany (Hamburg)		 All participants completed the survey only once after giving birth; survey included questions about CC or ENDS use during three prior time periods: 1) Pre-Pregnancy: year before pregnancy; 2) Early Pregnancy: First 3mo of pregnancy; 3) Late Pregnancy: Remainder of pregnancy (month 4 to birth) Before pregnancy: CC only (n=108; 20%), ENDS only (n=7; 1.3%), Dual users (n=35; 6.5%)
Early pregnancy: CC only (n=47; 8.7%), ENDS only (n=2; 0.4%), Dual users (n=0)
Late pregnancy: CC only (n=15; 2.8%), ENDS only (n=0), Dual users (n=0) Use definition: Any use of CC and/or ENDS during the time period.		 Transitions from Pre to Early Pregnancy:
97.1% of Dual Users stopped using ENDS
57.1% of Dual Users stopped smoking CCs
0% of CC smokers switched to ENDS

Individuals with low or medium (vs high) education attainment more likely to be dual users.
Stroud et al 2019 [66]
Dataset: Data drawn from larger study of smoking during pregnancy and fetal development (study not named)
Sample: Adult pregnant women (ages 18–40) no current/prior involvement with child protective services, and no history of serious gestational medical conditions; recruited from obstetric clinics, health centers and the surrounding community. (N=100; 50% reported CC smoking at least once during pregnancy (oversampled for CC smoking during pregnancy))
Location: United States (Southern New England)		 Timeframe captured by the ENDS use surveys covered 3mo pre-conception, through pregnancy, and 1mo post-partum.
4 interview sessions held at 2nd & 3rd trimesters and 1mo post-partum.
TP use data collected at each interview. ENDS flavor preference & perception surveys completed at one interview session in 3rd trimester.

Gestational age at enrollment: mean= 21 weeks (SD=1).
Interview sessions took place at 21±1, 27±1, and 33±1 weeks gestation and at 31±1 days postpartum.		 Prevalence ENDS use (full sample N=100):

Any use in lifetime: 45%

Any use in peripartum period: 16%

  • 3mo before pregnancy: 9%

  • During pregnancy: 9%

  • 1 mo post-partum: 3%

 Those reporting any lifetime use ENDS more likely (than never users) to smoke CC during pregnancy.

Among the 16% endorsing any ENDS use in peripartum period:
63% used ENDS more than one-time Flavors: 69% fruit, 19% candy, 19% mind, 13% tobacco, 6% spice, 6% coffee; 25% multiple flavors.
Pregnant persons endorsed greater preference and intention to use sweet flavors (fruit, candy) vs. tobacco flavors. -Perceived risk of ENDS use on general, pregnancy, and fetal health was high (but lower than perceived risk from CC smoking), and did not significantly differ by flavor.
Wang et al 2020 [47]
Dataset: PRAMS; 2016
Sample: Adult women who gave birth to singletons and provided complete information on CC and ENDS use (N=31,973)
Location: United States (nationally representative sample)		 Examined nicotine exposure in at 2 timepoints during pregnancy:

  1. Pre-pregnancy: 3mo before pregnancy

Late-pregnancy: last 3mo of pregnancy		 Pre-pregnancy TP Use (N=31,793):

  1. ENDS only (n=267; 1%)

  2. CC only (n=5,029; 14%)

  3. Dual users (n=976; 3%)

  4. No TP (n=25,521; 82%)

Late-pregnancy TP Use (N=31,793):

  1. ENDS only (n=126; 0.4%)

  2. CC only (n=2,632; 7%)

  3. Dual users (n=265; 0.6%)

  4. No TP (n=28,770; 92%)

 Transition Groups: Pre → Late Pregnancy:
Pre-pregnancy No TP (n=25,521)
No TP → No TP use (n=25,501; 99.9%)
No TP → CC only (n=17; 0.1%)
No TP → ENDS only (n=3; 0%)
No TP → Dual (n=0; 0%)
Pre-pregnancy ENDS only (n=267)
ENDS only → No TP (n=215; 81.7%)
ENDS only → CC only (n=3; 0.7%)
ENDS only → ENDS only (n=49; 17.6%)
ENDS only → Dual (n=0; 0%)
Pre-pregnancy CC only (n=5,029)
CC only → No TP (n=2,622; 55.1%)
CC only → CC only (n=2,342; 43.6%)
CC only → ENDS only (n=18; 0.3%)
CC only → Dual (n=47; 1.0%)
Pre-pregnancy Dual Users (n=976) Dual → No TP (n=432; 48.9%)
Dual → CC only (n=270; 25.9%)
Dual → ENDS only (n=56; 6.8%)
Dual → Dual (n=218; 18.4%)
Characteristics of Transition Groups:
CC only → ENDS only or Dual (vs. CC only → No TP use): younger, less educated, non-Hispanic white, unmarried
CC only → ENDS only or Dual (vs. CC only → CC only): younger, less educated, unmarried
Dual → No TP use (vs. Dual → Dual): more educated, nulliparous, received adequate prenatal care
Dual → ENDS only (vs. Dual → Dual or CC only): received adequate prenatal care
SECTION B. DESCRIPTION OF ENDS USE
Ashford et al 2016 [51]
Dataset: Cross-sectional dataset recruited from clinics in Kentucky.
Sample: Adult women (18–45) who currently use TP or used TP within the past 12 months; English-speaking; pregnant (recruited from prenatal clinic) or non-pregnant (recruited from women’s clinic) (N=194)
Location: United States (Kentucky)		 Categorized sample by pregnancy status:

  1. Pregnant (n=101)

  2. Non-pregnant (n=99)


No restrictions on timing within pregnancy or information on gestational age.		 Categorized participants by ENDS use status:

  1. Current ENDS Use (n=49; 25%)

  2. Former ENDS Use (n=77; 40%)

  3. Never ENDS Use (n=68; 35%)


To be eligible for study, participants needed to have used some form of TP within past 12 months.

Questions on reasons for using ENDS only given to those who ever used ENDS. Perceived risk ENDS questions asked of full sample.		 88% of current ENDS use group also reported current CC use; 46.9% of current ENDS use group were currently pregnant.

Pregnant (vs. non-pregnant) persons 51% less likely to be more frequent ENDS users (p=0.03).

Most common reasons for ENDS use: 1) To help quit CC smoking, 2) ENDS are cheaper than CC, 3) Can use ENDS where CC are prohibited, 4) ENDS are less harmful than CC.

Perception of ENDS as ‘serious’ (10.9%), ‘moderate’ (30.6%); ‘minor’ (38.3%); ‘no’ (20.2%) health risk.

In multivariate model, not-pregnant, younger age, White/Non-Hispanic race/ethnicity were associated with ENDS use; education, CC use status and perceived harm were not significantly related to ENDS use in the model.
Bhandari et al 2018 [28]
Dataset: Cross-sectional survey (2015)
Sample: Adult (>18 years old) pregnant women recruited from a women’s clinic; excluded women who had not heard of ENDS from the analysis (N=18) or incomplete data. (N=409, final analyses N=382)
Location: United States (Arkansas)		 All subjects were pregnant or post-partum at the time of survey completion: third trimester (55%); second trimester (26.3%); first trimester (11.0%); postpartum (7.2%).

ENDS use status groups did not differ in average gestational age (i.e., trimester).		 Participants were categorized into groups based on ENDS use status, then separately categorized based on ENDS and/or CC use status:
ENDS use status during pregnancy:

  1. Current ENDS Use (n=44; 11.9%)

  2. Former ENDS Use (n=71; 19.1%)

  3. Never ENDS Use (n=256; 69.0%)


ENDS and/or CC use status during pregnancy:

  1. ENDS and/or CC Use (n=230; 62.7%)

  2. Neither ENDS nor CC (n=137; 37.3%)

 Group Differences in ENDS Perceptions Beneficial in quitting smoking:
Current ENDS Use > Never ENDS Perceived risk of ENDS:
Never ENDS > Current ENDS Use
Never ENDS > Former ENDS Use

71% of current ENDS use group endorsed ever using ENDS to try to quit smoking CC.

74.6% of sample had adequate (i.e., score of ≥4) knowledge related to the facts and safety of ENDS, and this did not differ across ENDS use status.

Fewer participants reported being asked by their healthcare provider about their use of ENDS than their use of CC during pregnancy. This pattern was true regardless of ENDS and/or CC status of the participant.
Dobbs et al 2020 [69]
Dataset: Online survey; May-Dec 2017
Sample: Convenience sample of gestational women (currently pregnant, had been pregnant in past or planned to be pregnant in future); Ages 18–45; Recruited through social media (e.g., Facebook, Reddit). (N=218)
Location: United States		 Participants were categorized based on pregnancy status:

  1. Currently Pregnant (n=51)

  2. Previously (but not currently) Pregnant (n=103)

  3. Future Pregnant (n=64): Women who had never been pregnant, but planned to be pregnant in the future

No restrictions on timing within pregnancy or timeframe of plan for future pregnancy.		 Ever use of CCs and ENDS: any self-reported use in a subject’s lifetime (y/n).

Current use of CCs and ENDS: smoking or vaping “every day or some days” (y/n).		 37.7% of participants had ever tried ENDS; 19% of the Ever ENDS use group had used ENDS in the past 30 days.

Prevalence reporting Current ENDS Use significantly higher in the group who planned to be pregnant in the future (17.2%) compared to currently pregnant (5.9%), pregnant in the past (4.9%) groups.

Prevalence of lifetime ENDS use did not significantly differ by pregnancy status.

The full sample perceived risk of ENDS lower than risk of CC during pregnancy for a broad range of postnatal health outcomes. Ratings of perceived risk of ENDS or CC use during pregnancy were higher among the planned to be pregnant vs. currently pregnant group.

Reported healthcare providers less likely to ask about use or talk about risks (general or during pregnancy) of ENDS than to ask/talk about CC use and risks.
Fallin et al 2016 [55]
Dataset: Focus group interviews
Sample: Pregnant or recently postpartum women who reported using CCs and/or ENDS in the 3 months before their pregnancy or during their pregnancy (N=12).
Location: United States (Kentucky)		 Currently pregnant (n=8)

Recently Postpartum (n=4)		 Sample included persons who smoked CCs and/or used ENDS in the 3 months prior to pregnancy or during pregnancy. 4 focus group themes emerged:

  1. Attraction to ENDS as a harm reduction strategy (i.e., for smoking cessation and/or CC replacement)

  2. Uncertainty regarding the health effects of ENDS

  3. Ambivalence regarding novel product characteristics of ENDS

  4. Behaviors reflected dual use and often complete relapse to CCs
Hawkins et al 2020 [62]
Dataset: PRAMS restricted to state with ≥60% response rate.(2015–2016)
Sample: Women who gave birth to singletons; with complete information relevant to analysis (N=33, 964)
Location: United States (29 states and New York City)		 All women in the sample were pregnant at the time of survey completion.

Data on ENDS use and CC smoking relates to use during the last 3 months of pregnancy.		 Categorized into (Non-Exclusive) Categories Based on Use in Last 3 Mo Pregnancy:
Any ENDS Use (n=408; 1.2%)
 ENDS Only Use (n=170; 0.5%)

Any CC Use (n=2,615; 7.7%)
 CC Only Use (n=2,378; 7.0%)

Dual Use (n=272; 0.8%)		 Among ENDS use group:
43.2% used ENDS ≤1 day/week
10.4% used ENDS 2–6 days/week
16.0% used ENDS once/day,
30.5% used ENDS more than once/day ENDS use group more likely to be White or Other/Mixed Race/Ethnicity, have less years of education, and use CCs during pregnancy.

9.7% of those who smoke CCs and 0.5% of those who do not smoke CCs used ENDS prenatally.
Liu et al 2019 [52]
Dataset: National Health Interview Survey (NHIS); 2014–2017
Sample: Pregnant and non-pregnant adult women of reproductive age (18–44) enrolled in the NHIS (N=27,920)
Location: United States (nationally representative sample)		 Currently pregnant (n=1,071)

Non-pregnant (n=26,849)

No restrictions on timing within pregnancy or information on gestational age.		 Ever use of CCs and ENDS: any self-reported use in a subject’s lifetime (y/n).

Current use of CCs and ENDS: smoking or vaping “every day or some days” (y/n).		 Overall ENDS use:
Prevalence of current ENDS use did not significantly differ between pregnant (3.6%) and non-pregnant women (3.3%).
ENDS use by CC smoking status: Among pregnant persons: Prevalence of current ENDS use was higher among those who currently (38.9%) vs. formerly (1.3%) and never (0.3%) smoked CCs.
Among non-pregnant women: Prevalence of current ENDS use was higher among those who currently (13.5%) vs. formerly (8.8%) and never (0.7%) smoked CCs.
Mark et al 2015 [59]
Dataset: Cross-sectional survey; June-July 2014
Sample: All English-speaking women presenting to a university-based outpatient clinic for prenatal care June 2014-July 2014 (N=326 approached for inclusion; N=316 completed the survey)
Location: United States (Maryland)		 All participants were pregnant at the time of survey completion. No restrictions on timing in pregnancy.

Average gestational age at survey completion was 28 weeks.		 Participants were categorized into 2 groups based on ‘ever use’ of ENDS:

  1. ENDS Ever Use (n=42; 13%): any prior or current (past 30 day) use of ENDS

  2. ENDS Never Use (n=274; 87%)


Also asked about other TP use: current CC smoker defined as any CC smoking in past 30 days.

Asked to complete full survey on ENDS perceptions and motivations of use, even if in the Never ENDS Use group.		 0.6% (n=2) of ENDS Ever Users reported current daily ENDS daily. ENDS Ever (vs. Never ENDS) Use Groups:

  • More likely to be a current CC smoker (43% vs. 14%)

  • More likely to have tried pharmacological agent to quit CC, rated seriousness about quitting CC higher, but did not differ in likelihood or number of prior CC quit attempts

  • More likely to believe ENDS less harmful to self and baby, and cheaper, than CC

  • Groups did not differ in knowledge of harm of CC use during pregnancy

  • Slightly older, more likely to be White

Among Ever Use Group, perceived benefits of ENDS: Not as bad for my health (74%), may help quit smoking (73%), make easier to cut down on number CC (72%), use in places CC banned (55%), taste better (54%)
McCubbin et al 2020 [56]
Dataset: Cross-sectional data from a larger multi-center study of pregnant women (2016–2019)
Sample: Adult pregnant women (ages 18–44) in their first or second trimester, had used ENDS and/or CC in past 30 days, receiving prenatal care in one of three obstetric clinics in central Kentucky. (N=188; final analyses N=176)
Location: United States (Kentucky)		 All persons in the sample were currently pregnant and in either their first or second trimester. Subjects were categorized based on any past 30-day use of CC and/or ENDS :

  1. CC Only (n=110)

  2. Dual Use (n=66)


 ENDS Only use group was excluded from analyses and descriptions of ENDS use patterns due to insufficient sample size (n=12)

Dual Use (vs. CC only) Groups: Less likely smoke CC daily (70% vs 90%) Higher CC dependency (PSCDI) (11.8 vs 10.6) No significant difference in average CC/day or baseline demographics		 Among Dual Users (n=66)during pregnancy:
Daily ENDS use: 41%
<10 days/month ENDS use: 29%
10–15 days/month ENDS use: 29%
16–20 days/month ENDS use: 3%
# times/day ENDS used: median 8 (interquartile range=3–15)

Dual Users (vs. CC-Only) were less likely to perceive ENDS as harmful to general health (45% vs. 63%) and fetal health (41% vs. 60%) and more likely to rated ENDS use during pregnancy as acceptable; however, did not differ in the number of previous quit attempts.

Most commonly reported:
Reasons for using ENDS were help quit smoking CCs (83%), less expensive (49%), less harmful to self (46%), like taste/flavors (42%).
ENDS flavors used were fruit
(64%),mint/menthol (35%), candy or other sweets (27%).

Nicotine levels (in mg) of the e-liquid used in most recent ENDS were 1–6mg (54%), 7–12mg (16.4%), 19–25mg (8.2%), >25mg (4.9%). Only 8.2% reported using nicotine-free (0mg) e-liquids.
Obisesan et al 2020 [53]
Dataset: Behavioral Risk Factor Surveillance System Survey (BRFSS; 2016–2018)
Sample: Adult women (18–49); who were currently pregnant and
already enrolled in BRFSS (N=7,434)
Location: United States (nationally representative sample)		 All subjects were pregnant at the time of survey completion.

No restrictions on timing within pregnancy or information on gestational age.		 Categorized based on ENDS Use
  1. Ever ENDS Use (even once in lifetime)?
    1. Current ENDS Use (n=164; 2.2%)
      Daily (n=45; 0.6%)
      Occasional (n=115; 1.5%); some days
    2. Former ENDS Use (n=1,561; 21%)

  2. Never ENDS Use (n=5,709; 76.8%)



Additionally, categorized based on CC use:
Ever CC smoke >100 CC in lifetime?
Current CC Smoke (n=520; 7%)
Former CC Smoke (n=1,383; 18.6%)
Never CC Smoke (n=5,531; 74.4%)		 A majority of Current ENDS use group was young (69.2% <30 years), White (63.3%), single (57.6%), and employed (61.7%).

46.3% of Current ENDS use group also reported Current CC use (i.e., 1.1% of the total study sample were dual users). 30.1% of Current ENDS use group had never smoked CCs.

Pregnant Current ENDS use group (vs. never ENDS use group) had a higher prevalence of: Other tobacco use (3.6% vs. 0.5%) Marijuana use (46.8% vs. 3.1%)
Heavy alcohol use (12.0% vs. 1.3%)
Binge-drinking (24.1% vs. 2.6%)
Other high-risk behaviors, such as illicit drug use (22.6% vs. 6.0%)
Oncken et al 2017 [58]
Dataset: Part of a double-blind, placebo-controlled randomized clinical trial of NRT (nicotine inhaler) plus behavioral counseling for smoking cessation in pregnancy; enrollment 2012–2016.
Sample: Pregnant women <26 wks gestation, who smoked ≥ 5 CCs a day, and were unable to quit CC smoking; primarily recruited from two hospitals in Hartford CT and Springfield MA, plus private practice; who received the ENDS use questionnaires (N=103).
Location: United States
(Connecticut and Massachusetts)		 All participants in the sample were pregnant; pregnant persons who were at greater than 26 weeks of gestation were excluded. All participants reported current CC use. Overall sample was divided into 2 groups based on any lifetime ENDS use:

  1. ENDS Ever use (n=55; 53%)

  2. ENDS Never use (n=48; 47%)

 ENDS Use During Pregnancy 14% of participants used ENDS during pregnancy (10% used ENDS in the first trimester).

Mean (SD) days of ENDS use =7.5 (10.3) and frequency ENDS use/day= 6.4 (7.5)

N (%) who recall ENDS brand used= 5 (36%), used prefilled cartridges=7 (50%), reporting using to quit CC = 8(57%) or reduce CC use = 5 (36%).

Persons who used ENDS during pregnancy more likely to have a history of substance abuse and a greater number of previous smoking quit attempts.
Ever (vs. Never) ENDS use groups:

  1. Smoked more CC/day prior to pregnancy

  2. Had a greater number of previous CC smoking quit attempts

  3. Were more likely to be Hispanic or non-Hispanic White


15% of Ever ENDS Use group used ENDS as part of a past CC quit attempt.
Rollins et al 2020 [54]
Dataset: Telephone survey (2015–2018)
Sample: Pregnant women; Ages 16–45; recruited from an urban, low-income clinic, and flyers at local obstetric offices and community centers (N=1,476; final analysis N=1,365)
Location: United States (Rhode Island)		 All participants were pregnant at the time of the survey completion.

No restrictions on timing within pregnancy. Gestational age at the time of survey completion was
mean= 13.7 (SD=9.2) weeks

TP use categories based on current use (during pregnancy).

TP use questions asked about use at pre-conception (3mo pre-pregnancy) and during pregnancy.		 Categorized participants into three groups by current TP use status:

  1. ENDS Use (n=54; 4%); included in this group if used ENDS regardless of whether they also used CC or other TP.

  2. CC (but No ENDS) Use (n=372; 27%); use CC but not ENDS; not excluded for other TP use

  3. No TP or NRT use (n=939; 69%)


Participants who did not use ENDS or CC, but who used other TP or NRT were excluded from analysis (n= 111)		 74.1% of subjects who used ENDS also smoked CCs (i.e., Dual use), while 25.9% reported only ENDS use.

Among persons who smoked CC, those who also used ENDS smoked more CC per day (8.86 CC/day) than those who only used CC (6.18 CC/day).

ENDS use vs. CC only group: more likely to be White/Non-Hispanic (OR=2.48 (1.34–4.60)); have a higher level of education (OR=1.95 (1.02–3.72)) and household income (OR=2.84 (1.49–5.39)); and report depressive symptoms (OR=2.06 (1.00–4.22)).
ENDS use vs. No TP/NRT group: more likely to be White/Non-Hispanic (OR=4.25 (4.20–7.89)); report depressive symptoms (OR=4.28 (2.13–8.62)); and have a history of severe mental illness (OR=5.34 (2.3012.40)).
Wagner et al 2017 [64]
Dataset: Online survey using Amazon Mechanical Turk (MTurk); July–Aug 2015
Sample: Pregnant women; Ages 18–45; on MTURK (N=445)
Location: United States		 All participants were currently pregnant at the time of survey completion. No restrictions on gestational age at participation.

Gestational age at time of survey completion was mean=17.3 (SD=9.8) weeks in the sample overall. Gestational age significantly differed between the TP use group categories: CC only (21 (10.1)), ENDS only (13.8 (8.4)), Dual (13.8 (8.9)), No TP use (17.6 (9.9)).		 Categorized participants into 4 groups based on self-reported ENDS + CC use before and during pregnancy:

  1. No TP Use (n=353; 79.3%)

  2. CC only (n=25; 5.6%)

  3. ENDS only (n=29; 6.5%)

  4. Dual use (n=38; 8.84%)

 74.6% of ENDS only use group reported having switched to ENDS once learning they were pregnant.

ENDS only and Dual use groups were younger than CC only group, but did not differ by race, income, rurality.

Frequency of ENDS use during pregnancy did not significantly differ between exclusive ENDS use and dual use groups.

64.27% of all participants viewed ENDS as safer than CC in general, only 35.28% viewed ENDS as safer than CC for pregnant women. ENDS use (ENDS only or Dual) more likely than No TP Use group to report ENDS safer than CC in general and during pregnancy.

Abbreviations and Terms: TOBACCO-RELATED: TP=tobacco product (includes CC and ENDS and other tobacco products); ENDS=Electronic Nicotine Delivery Systems (note: ENDS refers to a category which includes e-cigarettes; although nicotine is in the name, we are using this term generally and products assessed in each study CANNOT be presumed to include nicotine just because they are referred to as ENDS); CC=Combustible cigarette; Dual Use= ENDS and CC use; EST, established user; EXP, experimental user; NRT= nicotine replacement therapy (e.g., nicotine patch or inhaler). STATISTICS: OR= Odds Ratio; aOR= Adjusted Odds Ratio; RR = Risk Ratio; M=mean, SD=Standard Deviation; CI=Confidence Interval. OTHER: BMI=-Body Mass Index; PRAMS= Pregnancy Risk Assessment Monitoring System; W=Wave, T=Timepoint.