Prenatal maternal nutrient supplementation has been reported to be associated with offspring obesity, but the reports are inconsistent and have mainly ignored the differences between the total children population and children born small for gestational age (SGA). This study aimed to examine the joint effects of folic acid, iron, and multivitamin supplementation during pregnancy on the risk of obesity in preschoolers born SGA. A total of 8918 children aged 3–6.5 years born SGA were recruited from Longhua District in Shenzhen of China in 2021. Their mothers completed a structured questionnaire about the child’s and parents’ socio-demographic characteristics, maternal prepregnant obesity, and mothers’ prenatal supplementation of folic acid, iron, and multivitamin. In addition, the children’s current weight and height were measured by trained nurses. Logistic regression models were used to analyze the associations between prenatal supplementations and the current presence of childhood obesity. After controlling for potential confounders, the results of the logistic regression analysis showed that prenatal supplement of folic acid (OR = 0.72, 95% CI = 0.55~0.93) was associated with a lower likelihood of being an obese preschooler born SGA. In contrast, the ingestion of multivitamin or iron supplements during pregnancy did not seem to be related to the likelihood of childhood obesity in preschoolers born SGA. Moreover, cross-over analysis of prenatal folic acid and multivitamin obtained significant negative associations of prenatal folic acid supplement only (OR = 0.73, 95% CI = 0.55~0.97) and combination supplement of folic acid and multivitamin (OR = 0.67, 95% CI = 0.50~0.90) with obesity of preschoolers born SGA; while the cross-over analysis of prenatal folic acid and iron observed significant negative associations between obesity of preschoolers born SGA and a combination supplement of folic acid and iron (OR = 0.70, 95% CI = 0.52~0.96). Furthermore, the aforementioned significant associations were only found in girls and not in boys when the analyses were stratified by sex. Our findings suggest that the prenatal folic acid supplementation may decrease the risk of obesity in preschool girls born SGA, and that this effect may be modified by prenatal multivitamin or iron supplementation.

Informed by the theory of developmental origins of health and disease, we conducted a survey among 66,854 mother–preschooler dyads in all kindergartens within the Longhua District of Shenzhen in China for exploring the combined effect of prenatal mosquito coil smoke (MCS) exposure and early postnatal nutritional status on obesity in preschoolers. A self-administered questionnaire was completed by mothers to collect parents’ and children’s socio-demographic characteristics, prenatal MCS exposure, child nutritional status at 1–3 years, etc., and children’s heights and weights were measured at the same time. After controlling for potential confounders, a series of logistic regression models and cross-over analyses were used to examine the independent and combination effects of prenatal MCS exposure and postnatal nutritional status on preschoolers’ obesity. We found that prenatal MCS exposure significantly increased the risk of preschoolers’ obesity (AOR = 1.14, 95%CI = 1.08–1.21). Additionally, early postnatal well-nourished nutritional status also increased the risk of preschoolers’ obesity (AOR = 1.56, 95%CI = 1.47–1.66). The cross-over analysis showed that the combination of prenatal MCS exposure with early general postnatal nutrition status (AOR = 1.22, 95%CI = 1.10–1.36) and early postnatal well-nourished nutrition status (AOR = 1.81, 95%CI = 1.65–1.97), respectively, increased the risk of preschoolers’ obesity. Our results indicated that prenatal MCS exposure and early postnatal nutritional status can independently and jointly increase the risk of preschoolers’ obesity.

Mosquito coils are efficient mosquito repellents and mosquito coil smoke (MCS) contributes to indoor air pollution. However, no prior population-based study has investigated whether prenatal MCS exposure is a risk factor for preterm birth (PTB) and whether exposure to MCS in different trimesters of pregnancy is associated with different levels of risk. The sample involved 66,503 mother–child dyads. Logistic regression models were used to examine the relationships between prenatal MCS exposure during different trimesters of pregnancy and PTB. We found that prenatal MCS exposure was associated with a greater likelihood of PTB (OR = 1.12, 95%CI: 1.05–1.20). The prenatal MCS exposure during the first trimester was associated with 1.17 (95%CI: 1.09–1.25) times the odds of being PTB, which was higher than exposure during the second trimester (OR = 1.11, 95%CI: 1.03–1.19) and during the third trimester (OR = 1.08, 95%CI: 1.01–1.16). In the stratified analysis, prenatal MCS exposure significantly increased PTB risk among girls but not among boys. Our results indicated that maternal MCS exposure during pregnancy was associated with PTB and that the first trimester might be the sensitive period. In light of these findings, public health interventions are needed to reduce prenatal exposure to MCS, particularly during the first trimester of pregnancy.