Electronic cigarette use during pregnancy and the risk of adverse birth outcomes: A cross-sectional surveillance study of the US Pregnancy Risk Assessment Monitoring System (PRAMS) population

Six studies observed no significant group differences in preterm birth rates between exclusive-vapers and non-users.

“Six of these studies observed no significant group differences in PTB rates [32, 42, 48, 50, 53, 54]”

Eight studies reported that exclusive-vaping did not have a significantly different risk of preterm birth than non-use.

“To summarise the findings for PTB/GA, eight studies reported that exclusive-vaping did not have a significantly different risk than non-use [32, 40, 42, 46, 48, 50, 53, 54]”

One study showed that quitting vaping during pregnancy versus continuing was not significantly associated with a reduced risk of SGA when controlling for smoking during the three months before pregnancy or in the last 3 months of pregnancy.

“One study showed that quitting vaping during pregnancy vs continuing was not significantly associated with a reduced risk of SGA when controlling for smoking during the three months before pregnancy or in the last 3 months of pregnancy [32].”

In one study, the association between quitting vaping during pregnancy and reduced LBW risk was not significant when focusing on those who did not smoke during the three months before pregnancy or in the last three months of pregnancy.

“However, when focusing the analysis on those who did not smoke during the three months before pregnancy, or in the last three months of pregnancy, this association was not significant.”

The largest sample size of exclusive-vapers was 977.

“The largest sample size of exclusive-vapers was 977 [32].”

The finding for the latter two PRAMS studies is inconsistent with five of the above PRAMS studies which found no difference between the groups.

“The finding for the latter two PRAMS studies is inconsistent with five of the above PRAMS studies which found no difference between the groups [32, 42, 50, 53, 54].”

The finding for the latter two PRAMS studies is inconsistent with six of the above PRAMS studies which found no group differences.

“Similar to the findings for PTB/GA, the finding for the latter two ‘PRAMS’ studies is inconsistent with six of the above PRAMS studies which found no group differences [32, 35, 42, 50, 53, 54].”

The largest sample of dual-users was 1,404.

“The largest sample of dual-users was 1,404 [32].”

In 17 studies it was not assessed whether any of those counted as vaping used non-nicotine vapes.

“and in 17 studies it was not assessed whether any of those counted as vaping used non-nicotine vapes [32, 35, 36, 38, 42, 43, 45, 46, 48–56].”

Among those who did not smoke during the three months before pregnancy or in the last three months of pregnancy, those who quit vaping had a significantly lower risk of preterm birth.

“however, among those who did not smoke during the three months before pregnancy or in the last three months of pregnancy, those who quit vaping had a significantly lower risk of PTB.”

Compared with those who continued to vape, those who quit vaping during pregnancy did not have a significantly lower risk of preterm birth.

“Another study found that compared with those who continued to vape, those who quit vaping during pregnancy did not have a significantly lower risk of preterm birth [32];”

Five studies observed no significant differences in preterm birth rates between dual-users and non-users.

“Five studies observed no significant differences in PTB rates between dual-users and non-users [32, 42, 50, 53, 54]”

Six of nine studies comparing dual-use and non-use reported a significantly higher prevalence of SGA for dual-users.

“Of nine studies comparing dual-use and non-use [32, 34–36, 42, 50, 52–54], six reported a significantly higher prevalence of SGA for dual-users [32, 42, 50, 52–54].”

Among eight studies comparing exclusive-vaping and non-use, four observed a higher likelihood of LBW for infants of exclusive-vapers.

“and four observed a higher likelihood of LBW for infants of exclusive-vapers [32, 43, 49, 50].”

Eight of ten studies comparing SGA or MBC prevalence between exclusive-vapers and non-users reported no significant differences.

“Eight of ten studies comparing SGA or MBC prevalence between exclusive-vapers and non-users reported no significant differences [32, 34, 35, 42, 46, 50, 53, 54].”

One study showed that quitting vaping during pregnancy versus continuing vaping was significantly associated with a reduced risk of LBW.

“One study showed that quitting vaping during pregnancy vs continuing vaping was significantly associated with a reduced risk of LBW [32].”

Of three studies comparing dual-users and non-users, one observed higher risk of LBW for dual-users.

“and the third observed higher risk of LBW for dual-users [32].”

Four studies reported that exclusive-vaping had a significantly higher risk of LBW/BW than non-use.

“and four reported that exclusive-vaping had a significantly higher risk [32, 43, 49, 50].”

In one study, the association between exclusive-vaping and LBW was not significant when adjusting for gestational age or when restricting the analysis to full-term births.

“In one of these studies the association between exclusive-vaping and LBW was not significant when adjusting for GA or when restricting the analysis to full-term births, indicating that effects on LBW could be mediated by PTB (although the risk of PTB was not significantly associated with exclusive vaping – see above) [32].”

There are conflicting findings for the five PRAMS studies for LBW/BW comparisons.

“For the latter comparisons, as for PTB/GA and SGA/MBC, there are conflicting findings for the five ‘PRAMS’ studies [32, 42, 43, 49, 50].”

The effects of exclusive-vaping on LBW could be mediated by preterm birth.

“indicating that effects on LBW could be mediated by PTB”