Cervical length, risk factors, and delivery outcomes among women with spontaneous preterm birth

To evaluate differences in risk factors and delivery outcomes among women with spontaneous preterm birth (sPTB) with short (≤25 mm) versus normal (>25 mm) cervical length (CL).

Secondary analysis of a prospective cohort study of singleton gestations between 18 0/7 and 23 6/7 weeks, without prior sPTB, undergoing universal transvaginal CL screening between 1 January 2012 and 31 December 2013. Only women with sPTB (<37 0/7 weeks) were included. Demographic characteristics, risk factors for sPTB, delivery outcomes and presentation of PTB were collected. The primary outcome was mean number of risk factors.

The cohort included 2071 women, of which 145 (7%) had PTB and 84 (4%) had sPTB. Sixty-nine (82%) women with sPTB had a CL >25 mm and 15 (18%) had a CL≤25 mm. Women with a short CL did not differ from women with normal CL with respect to demographic variables or mean number of risk factors (4.20 ± 2.11 versus 3.52 ± 1.97, p = 0.23), but they did deliver at a significantly earlier gestational age (25.0 ± 1.1 versus 34.6 ± 3.1 weeks, p < 0.01). The distribution of the presentation of sPTB was different in women with a short versus normal CL (p < 0.01).

Among women with sPTB, women with a short CL had similar number of risk factors, but were more likely to deliver at a significantly earlier gestational age. A short CL identifies women at risk for very early sPTB.