Association between urinary cotinine level and hypertensive disorders of pregnancy in women with uterine myoma: findings from the Japan Environment and Children's Study

The effect of smoking on hypertensive disorders of pregnancy is a public concern. Recent evidence suggests that the risk of hypertensive disorders of pregnancy is influenced by the presence of uterine fibroids. We explored the association between maternal smoking exposure and the risk of hypertensive disorders of pregnancy in relation to the presence of uterine fibroids using data from Japan's largest birth cohort study. This study focused on first-time mothers, and the study population comprised 2752 and 35,294 first-time mothers with and without uterine fibroids, respectively. Hypertensive disorders of pregnancy was categorized as early-onset (before 34 weeks) and late-onset (after 34 weeks). Maternal smoking exposure was assessed by measuring the urinary cotinine concentration during the mid-trimester. Participants were classified into four quartiles based on their urinary cotinine levels as follows: Q1 (low concentration) to Q4 (high concentration). Multivariate analysis adjusted for potential confounders revealed that in women without uterine fibroids, the Q3 urinary cotinine level was associated with a modified risk of early-onset hypertensive disorders of pregnancy (adjusted odds ratio: 0.63, 95% confidence interval: 0.44-0.89). Conversely, for women with uterine fibroids, Q4 urinary cotinine level was associated with an increased risk of hypertensive disorders of pregnancy (adjusted odds ratio: 1.68, 95% confidence interval: 1.05-2.72). In conclusion, this study indicated that the impact of maternal smoking exposure varied based on the presence of uterine fibroids, underscoring the importance of personalized preconception care.