Cervical length at mid-pregnancy and the risk of primary cesarean delivery.
BACKGROUND
Physiological and biochemical studies suggest that normal parturition at term is dependent on programmed development of the uterus in early pregnancy. It is recognized that a short cervix in mid-pregnancy is associated with an increased risk of spontaneous preterm birth. We hypothesized that a long cervix in mid-pregnancy would be associated with an increased risk of cesarean delivery during labor at term.


METHODS
We studied 27,472 primiparous women who had a cervical length of 16 mm or more at a median of 23 weeks of gestation and who ultimately delivered a live infant in labor at term.


RESULTS
The rate of cesarean delivery at term was lowest (16.0%) among women with a mid-pregnancy cervical length in the lowest quartile (16 to 30 mm) and was significantly greater in the second quartile (18.4%, 31 to 35 mm), third quartile (21.7%, 36 to 39 mm), and fourth quartile (25.7%, 40 to 67 mm) (P<0.001 for trend). The odds ratio for cesarean delivery among women in the fourth quartile, as compared with the first quartile, was 1.81 (95% confidence interval [CI], 1.66 to 1.97), and the odds ratio adjusted for maternal age, body-mass index, smoking status, race or ethnic group, gestational age at birth, spontaneous or induced labor, birth-weight percentile, and hospital of delivery was 1.68 (95% CI, 1.53 to 1.84; P<0.001). The increased risk of cesarean delivery was attributable to procedures performed for poor progress in labor.


CONCLUSIONS
The cervical length at mid-pregnancy is an independent predictor of the risk of cesarean delivery at term in primiparous women.
Smith
Gordon C S
GC
Department of Obstetrics and Gynaecology, Cambridge University, Cambridge, United Kingdom. gcss2@cam.ac.uk
Celik
Ebru
E
To
Meekai
M
Khouri
Olga
O
Nicolaides
Kypros H
KH
D000328:Adult; D054791:Cervical Length Measurement; D002584:Cervix Uteri / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D002585:Cesarean Section; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012306:Risk