Timing of mid‐trimester cervical length shortening in high‐risk women

Abstract

Objective To examine the natural history of cervical length shortening in women, who had experienced at least one prior spontaneous preterm birth at 17 + 0 – 33 + 6 weeks’ gestation. Methods Analysis of pre-randomization data from the multicenter Vaginal Ultrasound Cerclage Trial. Serial cervical length was measured by vaginal sonography in 1014 high-risk women at 16 + 0 to 22 + 6 weeks. We determined the time (in weeks’ gestation) to cervical length shortening <25 mm, or censoring, either by entering the randomized cerclage trial or attaining 22 + 6 weeks’ gestation. The incidence of cervical length shortening and the time to shortening were compared for women whose earliest prior preterm birth was in the mid-trimester, defined as <24 weeks versus at weeks 24–33. Similar comparisons were done based on each patient’s most recent birth history. Results Time to cervical length shortening by survival analysis was significantly shorter (Hazard Ratio [HR] = 2.2, p<0.0001) and the relative risk (RR) of shortening significantly higher (RR = 1.8, p<0.0001) for women whose earliest prior spontaneous preterm birth was <24 weeks. A larger effect was observed for women whose most recent birth was <24 weeks (HR = 2.8, p<0.0001; RR = 2.1, p<0.0001). The observed hazard ratios remained significant after adjusting for confounders in a multivariable Cox proportional hazards model. Conclusion Women with a prior spontaneous preterm birth <24 weeks are at a higher risk of cervical shortening, and do so at a higher rate and at an earlier gestational age, than do women with a later preterm birth history.

Cervical length measurement: Comparison of transabdominal and transvaginal approach

“…The data show that cervical length is not normally distributed; in line with the previous observations of Solomon, et al 22 While the cervix appears to have stable length < 24 weeks, there is then a gradual reduction in cervical length of approximately 1mm per week gestation thereafter; these cross‐sectional data are consistent with previous longitudinal assessment, showing a decay rate of 0.5 mm / week gestation 23 . There have been some reports that multiple measures of cervical length may be useful in defining an excessive rate of cervical decay from 16 weeks, that is predictive of preterm labour 24 . Our data, that show wide variation in TA and TV measurement made within individual patients would also suggest that multiple measures would only be of value if assessments were made transvaginally, as the degree of measurement variation seen with the TA approach would mask any objective assessment of cervical decay.…”

Follow-up cervical length in asymptomatic high-risk women and the risk of spontaneous preterm birth

“…26,[29][30][31][32][33][34][35][36][37] Many of these studies, however, evaluated low-risk women 29,30,32,34 or those with symptoms of preterm labor. 37 Several studies have evaluated cervical shortening in high-risk women finding conflicting results, with some suggesting it added additional predictive value, 26,31,33 whereas others found it did not.…”

“…26,[29][30][31][32][33][34][35][36][37] Many of these studies, however, evaluated low-risk women 29,30,32,34 or those with symptoms of preterm labor. 37 Several studies have evaluated cervical shortening in high-risk women finding conflicting results, with some suggesting it added additional predictive value, 26,31,33 whereas others found it did not. 35 Shortcomings of previous studies include the fact that many did not evaluate only those identified with a short cervical length, 26,[31][32][33][34] and studies that included only asymptomatic women with singleton gestations found to have a short cervical length did not evaluate other perinatal outcomes apart from preterm birth or gestational age at delivery.…”

“…37 Several studies have evaluated cervical shortening in high-risk women finding conflicting results, with some suggesting it added additional predictive value, 26,31,33 whereas others found it did not. 35 Shortcomings of previous studies include the fact that many did not evaluate only those identified with a short cervical length, 26,[31][32][33][34] and studies that included only asymptomatic women with singleton gestations found to have a short cervical length did not evaluate other perinatal outcomes apart from preterm birth or gestational age at delivery. 26,35 One study of asymptomatic high-risk women found that the cervical length measurement and the gestational age at transvaginal ultrasonography significantly affected the risk of spontaneous preterm birth.…”

“…[16][17][18][19] Cervical length measured by transvaginal ultrasonography has been shown to predict preterm birth in these asymptomatic high-risk women. 13,[20][21][22][23][24][25][26][27][28] Some studies have suggested that cervical length shortening by transvaginal ultrasonography may further increase the risk of preterm birth, 26,[29][30][31][32][33][34] whereas other studies have not noted this association. [35][36][37] There is a limited information regarding the benefit of follow-up cervical length ultrasound in high-risk asymptomatic women found to have a short cervical length.…”