Indoor air pollution from coal combustion and tobacco smoke during the periconceptional period and risk for neural tube defects in offspring in five rural counties of Shanxi Province, China, 2010–2016

•Impacts of multiple sourced indoor air pollution on the occurrence of neural tube defects were analyzed.•Indoor air pollution significantly increases the risk of conceiving neural tube defect infants among rural Chinese women.•Using coal stoves for heating and passive smoking are associated with increased possibility of neural tube defect occurrence. Indoor air pollution may increase the risk for neural tube defects (NTDs) in Chinese rural populations. However, this association remains a subject of debate. We conducted a population-based case-control study of 222 NTD and 517 control mothers recruited between 2010 and 2016 in five rural areas in northern China. An indoor air pollution exposure evaluation index (IAPEEI) was used to evaluate mothers’ exposure to tobacco-sourced and coal-sourced indoor air pollution. Essential characteristics were collected using structured questionnaires within 10 days of delivery. We found that exposure to indoor air pollution (IAPEEI ≥ 1) can lead to 3.41 times the risk of conceiving NTD fetuses compared with the no-exposure group (IAPEEI = 0) (adjusted odds ratio and 95 % confidence interval: 3.41 [2.34–5.02]). The risk increased with increasing IAPEEI score, indicating a clear dose–response trend (P