BACKGROUND-AIM:
Emerging smokeless nicotine products, such as oral nicotine pouches, are rapidly gaining popularity among young people. The addictive properties of these products raise questions about how using them during pregnancy may affect maternal and child health. Preeclampsia is a severe hypertensive pregnancy complication leading to considerable morbidity. The only definite cure is delivery making prevention crucial. Most research on nicotine exposure during pregnancy has focused on smoking, leaving the risks of smokeless products largely unknown. The Swedish smokeless tobacco product snus, together with oral nicotine pouches (introduced in 2016), have been registered in the Medical Birth Registry since 1999. This is offering a unique opportunity to study smokeless nicotine during pregnancy in a total-population cohort spanning more than two decades.

METHODS:
We analyzed singleton pregnancies (1999–2020) in the Swedish Medical Birth Registry, which captures 98% of births in Sweden and collects self-reported smokeless nicotine use at the first antenatal visit. Preeclampsia was identified using ICD codes O11, O13-O15. Follow-up was from first antenatal visit until delivery, preeclampsia diagnosis, or loss to follow-up. Cox regression was used in complete case analysis to estimate hazard ratios and 95% confidence intervals (CI), adjusting for carrying parent age, body mass index, smoking, parity, origin, delivery year and socioeconomic factors. Effect modification by calendar period (<2016 vs ≥2016, when oral nicotine pouches first were introduced) was explored.

RESULTS:
Preliminary adjusted hazard ratio for any preeclampsia among snus users was 1.13 (95% CI: 1.07–1.19) compared to non-users. The complete case cohort included 1 989 313 pregnancies and 100 209 preeclampsia events. Mean gestational age at first visit was 10.9 (±4.7) weeks. Mean follow-up time was 187±40.9 days for preeclampsia cases and 206±37.0 days for pregnancies censored for any reason. Effect modification analyses assessed if the introduction of oral nicotine pouches in 2016 had an impact on the association. Post-2016 (oral nicotine pouch era), the preliminary adjusted hazard ratio was 1.15 (95% CI: 1.02–1.29) for snus users compared to snus users in earlier years.

CONCLUSIONS:
Our study suggests that there is a difference between previous findings from smokers and now smokeless nicotine users during pregnancy on preeclampsia hazard. The higher hazard ratio after oral nicotine pouches were introduced, may reflect the high nicotine content in these products, although this needs to be explored further. Further analyses will refine confounding control. These results underscore the need for updated clinical guidelines and public health measures addressing smokeless nicotine use in pregnancy.