Household incense burning and small for gestational age risk in newborn infants

In East Asia, incense burning for religious and ceremonial purposes is a long-standing cultural practice. However, incense combustion generates particulate matter and toxic pollutants that may adversely affect maternal and fetal health. Associations between maternal incense exposure and pre-eclampsia, adverse neurodevelopmental outcomes, and impaired fetal growth are noted. Evidence regarding the association between household incense burning and small for gestational age (SGA), particularly according to gestational-age strata, remains limited.

We analyzed data from 18,666 mother-infant pairs enrolled in the Taiwan Birth Cohort Study with follow-up at 6 months postpartum. Household incense-burning exposure during pregnancy was categorized as none, occasional, or daily. Multivariable logistic regression models were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for SGA, stratified by term and preterm births. Multiple sensitivity analyses were conducted to assess the robustness of the findings, including adjustments for additional indoor environmental factors, maternal medical history, gestational complications, gestational weight gain, and evaluation of interactions with secondhand-smoke exposure.

Overall, 583 (8.1%) SGA infants were identified in the non-exposure group (n = 7242), 415 (9.4%) in the occasional-exposure group (n = 4413), and 700 (10.0%) in the daily exposure group (n = 7011). Among term infants, household incense burning was significantly associated with SGA, with aORs of 1.16 (95%CI: 1.00-1.33) for occasional exposure and 1.25 (95%CI: 1.10-1.41) for daily exposure, demonstrating a dose-response relationship. Similar, but nonsignificant, patterns were observed among preterm infants. No significant association was found between household incense burning and preterm birth.

In this large population-based cohort, maternal exposure to household incense burning during pregnancy was associated with increased risk of delivering an SGA infant, particularly among term births. The risk was higher for daily than for occasional exposure. These findings highlight the potential public health implications of household incense use during pregnancy.