Water-pipe tobacco and cigarette smoking, on preeclampsia: adverse or protective effect: MATCH cohort study

While cigarette smoking has been paradoxically associated with a reduced risk of preeclampsia, the effect of waterpipe (WP) smoking, an increasingly prevalent form of tobacco use remains poorly understood. This study aimed to investigate and compare the independent associations of cigarette and WP smoking with the risk of developing preeclampsia.

This prospective cohort study, conducted within the MATCH study at Arash Women's Hospital, Tehran, Iran (2020-2023), enrolled 1,856 first-trimester pregnant women (18-45 years) without chronic/metabolic conditions, following them until delivery. The main outcome was preeclampsia, defined per ACOG (2020) criteria as new-onset hypertension (≥140/90  mmHg on two occasions ≥ 4  h apart) with proteinuria (≥300  mg/24  h, protein‑to‑creatinine ratio ≥ 0.3  mg/mg, or dipstick ≥ 2 + ) after 20  weeks' gestation. Smoking status and covariates were assessed via questionnaires and clinical measurements. Adjusted risk ratios (aRRs) were estimated using modified Poisson regression, controlling for confounders identified via directed acyclic graphs (DAGs).

During follow-up, 92 women (4.95%) developed preeclampsia. Current cigarette smoking was associated with a significantly lower risk compared to never-smoking (aRR 0.48; 95% CI 0.25-0.90). In contrast, current WP smoking showed no significant association (aRR 0.74; 95% CI 0.39-1.41). Former and passive WP smoking also demonstrated no significant risk differences.

Cigarette smoking during pregnancy was associated with a reduced risk of preeclampsia, while WP smoking showed no significant effect. These findings suggest divergent impacts of different tobacco use modalities and underscore the need for further research into the underlying mechanisms.