The use of a variable cut-off value of cervical length in women admitted for preterm labor before and after 32 weeks.
OBJECTIVE
To determine whether the optimal cut-off value to predict low risk of preterm delivery in women admitted for preterm labor should be adjusted for gestational age.


METHODS
A cohort of 333 women with singleton pregnancies admitted with preterm labor and intact membranes between 24 and < 36 weeks' gestation was studied. The women were categorized according to prematurity into one of two groups: those admitted at < 32 weeks (Group 1, very preterm) and those admitted at >or= 32 weeks (Group 2, preterm). Transvaginal ultrasound was performed 24-48 h after admission and cervical length measured. The predictive value of different cut-off points was explored. Outcome variables were spontaneous preterm delivery within 7 days of admission and delivery at < 34 weeks.


RESULTS
The mean ( +/- SD) gestational ages at admission and delivery were 31.9 ( +/- 2.6) and 37.5 ( +/- 2.2) weeks, respectively, and the mean ( +/- SD) cervical length was 30.4 ( +/- 8.9) mm. The rates of spontaneous delivery within 7 days and at < 34 weeks were 6.3 and 7.0%, respectively. The cut-off value of 15-mm cervical length showed a sensitivity, negative predictive value and false positive rate for delivery within 7 days of 0, 96.5 and 2.7% in the very preterm group, and 35.3, 94.6 and 4% in the preterm group, respectively. For a cut-off point of 25 mm, these values were 75, 99 and 14.3%, and 70.6, 96.8 and 24.5%.


CONCLUSIONS
The predictive value of different cut-off points of cervical length is similar at different gestational ages. However, the higher false positive rate after 32 weeks' gestation might justify the adoption of gestational-age related cut-off values in clinical protocols. In women admitted at < 32 weeks' gestation, a cut-off point of 25 mm may be used to predict a low risk of preterm delivery, whereas in women admitted at 32 weeks or later, 15 mm might be more appropriate. Published by John Wiley & Sons, Ltd.
Palacio
M
M
Prematurity Unit, Department of Maternal Fetal Medicine, Institut Clínic de Ginecologia, Obstetrícia i Neonatologia, Hospital Clínic de Barcelona, Barcelona, Spain. mpalacio@clinic.ub.es
Sanin-Blair
J
J
Sánchez
M
M
Crispi
F
F
Gómez
O
O
Carreras
E
E
Coll
O
O
Cararach
V
V
Gratacós
E
E
D000328:Adult; D002584:Cervix Uteri / Q000000981:diagnostic imaging / Q000473:pathology*; D004812:Epidemiologic Methods; D005260:Female; D005865:Gestational Age; D006801:Humans; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging / Q000473:pathology*; D011247:Pregnancy; D014463:Ultrasonography