Population and data collection
In this epidemiologic, monocentric, observational, longitudinal and retrospective study, data derive from the administrative and medical databases of the University Hospital of Martinique, which is the main obstetric center in Martinique dealing with an average of 3050 births per year, over an average of 3600 births per year out of a population of approximately 380 000 inhabitants. Pregnant women residing in Martinique, a French Caribbean oversea Island were recruited from the Mother and Child Centre of the University Hospital of Martinique. Mean age, body mass index (BMI), tobacco use, medical and surgical information as well as specific information regarding the pregnancy and obstetrical history and complications of the ongoing pregnancy were recorded. We restricted the study to those with pregnancy (determined by ultrasound dating scan before 12 weeks and date of delivery) during the period from 25/01/2016 to 31/07/2020. To be included in the present study, the women had to have at least 18 years old, a gestational age of 20 weeks or more, and be registered and followed-up at the CHUM Mother and Child Centre. From the eligible population, we excluded the women who were unable or refuse to consent and having pregnancy with more than two baby at a time. We also excluded those women with moving geographical location during the pregnancy period, making difficult to determine the actual exposure to air H2S pollution.