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Introduction: Air pollution is a current major health issue. The burden of airborne pollutants and aeroallergen levels varies throughout the year, as well as their interaction and consequences. Prenatal exposure during pregnancy has been associated with adverse perinatal outcomes. The aim of this study was to evaluate the impact of air pollutants on perinatal outcomes in patients with or without respiratory allergy. Material and methods: Nested case–control retrospective study on 3006 pregnant women. Correlations between concentrations of common pollutants in each trimester of pregnancy and on average during the whole pregnancy and both gestational age at delivery and birthweight were studied. Pearson's correlation coefficient and binary logistic regression were used. Results: In general, pollutants correlated more strongly with birthweight than with gestational age at delivery. Nine‐month NO2, SO2, CO, and benzene, and second‐trimester CO negatively correlated with birthweight, whereas only first‐trimester NO2 showed a very mild correlation with gestational age at delivery. Negative correlations between pollutants and birthweight were much stronger in the respiratory allergy group (n = 43; 1.4%) than in the non‐allergic group. After adjustments, the most significant predictive pollutant of birthweight was SO2 in both groups. The best predictive model was much stronger in the allergic group for third‐trimester SO2 (R2 = 0.12, p = 0.02) than in the non‐allergic group for total SO2 (R2 = 0.002, p = 0.02). For each unit that SO2 increased, birthweight reduced by 3.22% vs. 1.28% in each group, respectively. Conclusions: Air pollutant concentrations, especially SO2, negatively influenced birthweight. The impact of this association was much stronger and more relevant in the group of women with respiratory allergies. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the influence of respiratory allergy on obstetrics and perinatal outcomes. Methods: A nested case–control retrospective study on 41 035 pregnant women. Obstetrics and perinatal outcomes of women with or without respiratory allergy were compared. Rates of preterm delivery (<37 weeks of gestation), low birth weight (<2500 g), neonatal acidosis (pH < 7.20), low 5‐min APGAR score (<7), cesarean section rate and indications, and perinatal morbidity and mortality were analyzed. Results are expressed as number and percentages. χ2 and Fisher exact tests were used for comparisons. Logistic regression was used. Statistical significance was set at 95% level (P < 0.05). Results: A total of 724 (1.8%) patients had respiratory allergy, and their rates of preterm delivery and low birth weight were significantly higher than those of control women (both P < 0.001). Nevertheless, analyzing the causes, multiple gestation rate was significantly higher in this group, and adjusting by this, no statistical difference was found in any of the perinatal outcomes studied. In addition, in vitro fertilization and sterility were also significantly higher in the respiratory allergy group (both P < 0.001). Conclusion: Women with respiratory allergy are at higher risks of prematurity and low birth weight but these results are mediated by sterility, in vitro fertilization, and multiple gestation rate. Nonetheless, participation of inflammatory mechanisms should be further studied. Synopsis: Women with respiratory allergies are at higher risk of prematurity and low birth weight, but these results are mediated by sterility, IVF, and multiple gestation rate. [ABSTRACT FROM AUTHOR]