Abstract Preterm birth (PTB) is the main condition related to perinatal morbimortality worldwide. The aim of this study was to identify gene-environment interactions associated with spontaneous PTB or its predictors. We carried out a retrospective case-control study including parental sociodemographic and obstetric data as well as newborn genetic variants of 69 preterm and 61 at term newborns born at a maternity hospital from Tucumán, Argentina, between 2005 and 2010. A data-driven Bayesian network including the main PTB predictors was created where we identified gene-environment interactions. We used logistic regressions to calculate the odds ratios and confidence intervals of the interactions. From the main PTB predictors (nine exposures and six genetic variants) we identified an interaction between low neighbourhood socioeconomic status and rs2074351 (PON1, genotype GG) variant that was associated with an increased risk of toxoplasmosis (odds ratio 12.51, confidence interval 95%: 1.71 - 91.36). The results of this exploratory study suggest that structural social disparities could influence the PTB risk by increasing the frequency of exposures that potentiate the risk associated with individual characteristics such as genetic traits. Future studies with larger sample sizes are necessary to confirm these findings.

OBJECTIVES: To determine the frequency of smoking and second-hand smoke exposure among pregnant women in Ecuador and to describe the sociodemographic profiles associated with these perinatal risk factors. METHODS: A cross-sectional descriptive study using a survey of women 18-46 years of age who were more than three months pregnant and attended follow-up consultations in seven maternity clinics in six cities in Ecuador between October 2004 and September 2005. Demographics and environmental exposure (independent variables) data and their relationship to cigarette smoking and secondhand-smoke exposure were analyzed. RESULTS: Of the 746 women studied, 53.3% had smoked occasionally, and 4.3%, regularly; of these, 75% had quit smoking before or during pregnancy. Of the respondents, 12.9% were frequently or always exposed to secondhand smoke indoors. Having more education (11 or more years), being in the middle or upper socioeconomic classes, being Caucasian, and it being considered acceptable for women in the community to smoke were significantly and directly associated with cigarette smoking (P < 0.001). Overall, 12.9% of women were being exposed to secondhand smoke and this was significantly associated with being single and cohabiting with smokers or employees connected to the tobacco industry (P < 0.001). CONCLUSIONS: Specific measures must be designed and implemented to not only encourage smoking cessation during pregnancy, but also to prevent women of reproductive age from taking up smoking and to limit smoking in the home environment.

OBJETIVOS: Determinar la frecuencia de tabaquismo y exposición ambiental al humo de tabaco en mujeres embarazadas de Ecuador y describir los perfiles sociodemográficos asociados con esos factores de riesgo perinatal. MÉTODOS: Estudio descriptivo transversal mediante una encuesta aplicada a mujeres de 18 a 46 años con más de 3 meses de embarazo que asistieron entre octubre de 2004 y septiembre de 2005 a sus consultas de seguimiento en siete servicios de maternidad de seis ciudades de Ecuador. Se analizaron los datos demográficos y de exposición medioambiental (variables independientes) y su relación con el hábito de fumar cigarrillos y la exposición ambiental al humo de tabaco. RESULTADOS: De las 746 mujeres analizadas, 53,3% había fumado ocasionalmente y 4,3% había fumado habitualmente; de estas, 75,0% había dejado de fumar antes o durante el embarazo. De las encuestadas, 12,9% estuvo expuesta con frecuencia o siempre al humo de tabaco en ambientes cerrados. Tener mayor educación (11 años o más) y un nivel socioeconómico medio o alto, ser caucásica y considerar aceptable que las mujeres de su comunidad fumen se asoció significativa y directamente con el hábito de fumar cigarrillos (P < 0,001). En general, 12,9% de las mujeres estuvo expuesta al humo de tabaco y esto se asoció significativamente con ser soltera y cohabitar con fumadores o trabajadores vinculados con la industria del tabaco (P < 0,001). CONCLUSIONES: Se deben diseñar e implementar medidas específicas dirigidas no solo a estimular el abandono de este hábito en las embarazadas, sino también a prevenir que las mujeres en edad reproductiva comiencen a fumar y controlar el entorno fumador en el hogar.