Grant: Project Grant

Preterm birth occurs in about 8% of deliveries in Canada and is a leading cause of infant death and health complications throughout the life course. There are several known risk factors of preterm birth, like having a history of a previous preterm birth, being underweight or obese, or smoking during pregnancy, but the cause of most cases of preterm birth are still not known. Some studies have found a link between having an emergency cesarean delivery late in labour (when a person's cervix is fully dilated) and having a preterm birth in a future pregnancy. However, these studies have several problems that make it difficult to know if this relationship is true (e.g., inappropriate comparison groups, not accounting for important differences in people who do and do not have a cesarean late in labour). In order to investigate this link, we need to compare the risk of preterm birth in a future pregnancy between individuals who had a late stage cesarean delivery with those who had the only other alternative types of delivery. These alternatives are forceps or vacuum delivery, which are instrument-assisted deliveries that help to delivery the baby through the vagina. We will use information on all births in four provinces in Canada to create a group of 933,000 deliveries from 2001-2022. Among these deliveries, we will compare the rates of preterm birth in a future delivery between individuals with forceps, vacuum or late stage cesarean deliveries. We will also examine whether there is a link between having an injury to the cervix during delivery and having a preterm birth in a future pregnancy. Lastly, we will also look for trends in the relationships between these deliveries and preterm birth using 21 years of birth information. These studies may uncover opportunities to reduce preterm births and may help provide important information for individuals who have the opportunity to decide between having a forceps, vacuum, and late stage cesarean delivery.