Association between prenatal exposure to cooking oil fumes and full-term low birth weight is mediated by placental weight

Objective: Evidence regarding the association between prenatal exposure to cooking oil fumes (COF) and full-term low birth weight (FTLBW) is still controversial, and the mechanism remains unclear. This study thus aims to explore the association of prenatal COF exposure with off-spring FT-LBW as well as the mediating role of placenta in their association. Methods: A case-control study enrolling 266 pregnant women delivering FTLBW newborns (cases) and 1420 delivering normal birth weight (NBW) newborns (controls) was conducted. Information on prenatal COF exposure, socio-demographics, and obstetric conditions were collected at the Women's and Children's Hospitals of Shenzhen and Foshan in Guangdong, China. Linear and hierarchical logistic regression models were undertaken to explore the associations among COF exposure, placenta and birth weight, as well as the mediation effect of placental weight. Results: After controlling for potential confounders, prenatal COF exposure was significantly associated with the higher risk of FT-LBW (OR = 1.31, 95% CI= 1.06–1.63) and the lower placental weight (ß = −0.12, 95% CI= −0.23 ~ −0.005). Compared with mothers who never cooked, those cooking sometimes (OR= 2.99, 95% CI= 1.48–6.04) or often (OR= 3.41, 95% CI= 1.40–8.34) showed a higher risk of FT-LBW, and likewise, those cooking for less than half an hour (OR= 2.08, 95% CI= 1.14–3.79) or cooking between half to an hour (OR= 2.48, 95% CI= 1.44–4.29) were also more likely to exhibit FT-LBW. Different cooking methods including pan-frying (OR= 2.24, 95% CI= 1.30–3.85) or deep-frying (OR= 1.78, 95% CI= 1.12–2.85) during pregnancy were associated with increased FT-LBW risks as well. The further mediation analysis illustrated that placental weight mediated 15.96% (95% CI: 12.81~28.80%) and 15.90% (95% CI= 14.62%~16.66%) of the associations of cooking during pregnancy and frequency of prenatal COF exposure, respectively, with FT-LBW.