MedWire News: Primiparous women are more likely to need a cesarean delivery at term if they have a relatively long cervical length at mid-pregnancy, study findings show.

Gordon Smith (Cambridge University, UK) and colleagues found that women with cervical lengths of 40-67 mm at mid pregnancy were 1.81 times more likely than women with cervical lengths of 16-30 mm to need cesarean deliveries.

This increased risk remained, at an odds ratio of 1.68, after taking into account 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.

The researchers studied 27,472 primiparous women who had a cervical length of 16 mm or more at a median of 23 weeks' gestation.

Women with a mid-pregnancy cervical length in the lowest quartile (16-30 mm) had the lowest rate of cesarean delivery, at 16.0 percent. This was significantly greater than the rates of 18.4 percent for those in the second quartile (31-35 mm), 21.7 percent for those in the third quartile (36-39 mm), and 25.7 percent for those in the fourth quartile (40-67 mm).

Our findings suggest that "poor progress during labor in women who deliver at term may be related to dysfunctional development of the uterus at much earlier stages of pregnancy," Smith et al conclude.

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