1. Danish Headache Center (VV-C, JJK, RHJ), The Rigshospitalet-Glostrup, University of Copenhagen; Department of Neurology (DB), Odense University Hospital; Department of Clinical Research (DB), University of Southern Denmark; OPEN (DB), Odense Patient Data Explorative Network, Odense University Hospital; and Department of Obstetrics (LB), Rigshospitalet, University of Copenhagen, Denmark.