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. Author manuscript; available in PMC: 2014 Sep 11.
Published in final edited form as: Ultrasound Obstet Gynecol. 2013 Jan 8;41(2):152–161. doi: 10.1002/uog.12344

Table 1. Demographics of the studied population.

Maternal characteristics
Age, completed years, median (range) 23 (17-41)
Number of pregnancies, n, median (range) 1 (1-14)
Gestational age at ultrasound, weeks + days, median (range) 21+ 4 (8+2-40+3)
Cervical length, mm, median (range) 36 (25-52)
Prior preterm delivery, n, (%) 55 (21)