Change in cervical length in cases resulting in threatened preterm labor.
OBJECTIVE
To determine the predisposing changes in cervical length (CL) and the critical range of CL in which significant uterine contractions emerge resulting in threatened preterm labor (TPL).


METHODS
Sixty-eight uncomplicated singleton pregnancies where the CL was <25 mm before 31 weeks were divided into cases with TPL (n = 23) or without (n = 45). CL and uterine contractions were monitored sequentially starting between 16 and 20 weeks. The gestational ages when a CL of <25 or <15 mm was first observed, the interval between these two measurements, and the CL value at TPL diagnosis were analyzed retrospectively.


RESULTS
(1) The gestational ages when a CL of <25 and <15 mm was first detected were lower in the TPL group (25 (median); 18-30 (range) and 28; 25-33 weeks, respectively) than in the non-TPL group (27; 20-30 and 33; 26-35 weeks; P = 0.030 and P < 0.001). (2) The interval between the two measurements was shorter in the TPL group (2.5; 0-15 weeks) than in the non-TPL group (5.5; 0-13 weeks, P = 0.034). (3) The CL value at TPL diagnosis was 13 mm (median), ranging from 7 to 18 mm.


CONCLUSIONS
Cases with early onset and subsequent rapid CL shortening before 31 weeks resulted in TPL when CL decreased below the range 7-18 mm.
Center for Maternal, Fetal and Neonatal Medicine, Fukuoka University Hospital, 7-45-1 Nanakuma, Jonan, Fukuoka, 814-0180, Japan. ty-obgyn@cis.fukuoka-u.ac.jp.
Toshiyuki
T
Yoshizato
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Hiroshi
H
Tsujioka
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Shinji
S
Horiuchi
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Kyoko
K
Shirota
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Hirotsugu
H
Obama
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Takeshi
T
Nojiri
Department of Biochemistry School of Medicine, Fukuoka University, Fukuoka, Japan.
Fusanori
F
Yotsumoto
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka, Japan.
Shingo
S
Miyamato
Cervical length; Threatened preterm labor; Transvaginal ultrasonography