Bed Rest With a Short Cervix on Preterm Birth

Maternal AR has long been used to prevent PTB. However, definitions of AR vary widely, ranging from complete bed rest to partial limitation of physical activity for one or more hours daily. The use of maternal AR to prevent preterm birth is largely based on observational evidence linking strenuous physical activity to an increased risk of preterm birth, and the assumption that reduced activity may decrease myometrial activity. However, the existing evidence on the clinical effects of AR remains limited and has not demonstrated a reduction in preterm birth or a delay in deliv-ery. In contrast, some studies suggest a potential increase in preterm birth following AR and instead significant adverse maternal and fetal effects. The overall aim of this study is to compare gestational age at birth in women with a short cervix who are prescribed AR compared with women with a short cervix who are not prescribed AR (NAR). The primary hypothesis is that NAR is non-inferior to AR in prolonging pregnancy in women with a short cervix. Secondary hypotheses are that, compared with AR, NAR is associated with higher level of physical activity, lower risk of maternal depression, and reduced risk of loss of maternal bone mineral density. Through the BEWISE study, we wish to implement a change in the Danish national clinical practice regarding AR from recommending AR in risk groups (current practice) to no longer recommending AR as part as routine care (new practice). We will evaluate this change in clinical practice by prospectively collecting data from women both before and after implementation of the new recommendation. The transition from AR to NAR will be implemented sequentially in each Danish region using a randomised stepped-wedge (SW) cluster design, with each region constituting a cluster. The order in which regions transition is determined by randomisation. Each region will adopt the new recommendation at 3-month intervals, resulting in full national transition from AR to