title: Authors' reply to Fountain and colleagues.
authors.affiliation: Queen Charlotte's and Chelsea Hospital, Imperial College, London W12 0HS, UK tbourne@imperial.ac.uk.
authors.forename: Tom
authors.initials: T
authors.lastname: Bourne
authors.affiliation: Queen Charlotte's and Chelsea Hospital, Imperial College, London W12 0HS, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: Preisler
authors.affiliation: Department of Development and Regeneration, KU Leuven, Belgium.
authors.forename: Ben
authors.initials: B
authors.lastname: Van Calster
authors.affiliation: Department of Development and Regeneration, KU Leuven, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Timmerman
mesh_terms: D000022:Abortion, Spontaneous / Q000000981:diagnostic imaging*; D005260:Female; D058746:Gestational Sac / Q000000981:diagnostic imaging*; D006801:Humans; D011247:Pregnancy; D016216:Ultrasonography, Prenatal