The primary outcome is to determine whether daily LDA initiated between 6 0/7 weeks and 13 6/7 weeks and continued to 36 0/7 weeks reduces the risk of preterm birth (birth prior to 37 0/7 weeks of pregnancy) by 20%. This will be determined based on assessed date of delivery in comparison to the projected estimated date of delivery, independent of whether or not the preterm delivery is iatrogenic or spontaneous.