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Cervical length at 23 weeks of gestation: prediction of spontaneous preterm delivery.
Heath VC, Southall TR, Souka AP, Elisseou A, Nicolaides KH.
Ultrasound Obstet Gynecol 1998;12:312-7. -
Cervical length at 23 weeks of gestation: relation to demographic characteristics and previous obstetric history.
Heath VC, Southall TR, Souka AP, Novakov A, Nicolaides KH.
Ultrasound Obstet Gynecol 1998;12:304-11.