Strain at the internal cervical os assessed with quasi-static elastography is associated with the risk of spontaneous preterm delivery at ≤34 weeks of gestation

Abstract

Aim: To evaluate the association between cervical strain assessed with quasi-static elastography and spontaneous preterm delivery.

Methods: Quasi-static elastography was used to estimate cervical strain in 545 pregnant women with singleton pregnancies from 11 weeks to 28 weeks of gestation. Cervical strain was evaluated in one sagittal plane and in the cross-sectional planes of the internal cervical os and external cervical os. The distribution of strain values was categorized into quartiles for each studied region and their association with spontaneous preterm delivery at ≤34 weeks and at <37 weeks of gestation was evaluated using logistic regression.

Results: The prevalence of spontaneous preterm delivery at <37 weeks of gestation was 8.2% (n=45), and that at ≤34 weeks of gestation was 3.8% (n=21). Strain in the internal cervical os was the only elastography value associated with spontaneous preterm delivery. Women with strain values in the 3rd and 4th quartiles had a significantly higher risk of spontaneous preterm delivery at ≤34 weeks and at <37 weeks of gestation when compared to women with strain values in the lowest quartile. When adjusting for a short cervix (<25 mm) and gestational age at examination, women with strain values in the 3rd quartile maintained a significant association with spontaneous preterm delivery at ≤34 weeks (OR 9.0; 95% CI, 1.1-74.0; P=0.02), whereas women with strain values in the highest quartile were marginally more likely than women with lowest quartile strain values to deliver spontaneously at ≤37 weeks of gestation (OR 95% CI: 2.8; [0.9-9.0]; P=0.08).

Conclusion: Increased strain in the internal cervical os is associated with higher risk of spontaneous preterm delivery both at ≤34 and <37 weeks of gestation.

Figure 1

Cervical elastography; upper panel, cross-sectional plane of the internal cervical os: a) strain in the endocervical canal, b) strain in the entire cervix; lower panel, sagittal plane of the cervix: c) strain in the endocervical canal, d) strain in the entire cervix.

Figure 2

Prevalence of spontaneous preterm delivery at ≤34 and at <37 weeks of gestation by internal os endocervical strain quartile (A and B), and by internal os entire cervix strain quartile (C and D). Endocervical strain quartiles were defined as: 1st quartile ≤0.16; 2nd quartile >0.16–0.27; 3rd quartile >0.27–0.41; and 4th quartile >0.41. Entire cervix strain quartiles were defined as: 1st quartile ≤0.29; 2nd quartile <0.29–0.4; 3rd quartile >0.4–0.52: and 4th quartile >0.52.