Table 6. Summary of studies predicting spontaneous preterm birth using elastography.
| Year | Study | Design | Risk group | Total | Prevalence of sPTD | Ultrasound system | Compression | ROI | Assessment of elastography | Comparison | Results |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2014 | Köbbing et al.18 | Prospective cohort study | Low-risk (11–36 wk) | 182 | 17 (11.9) | Toshiba Aplio XG | External (manually) | Four circular ROIs in anterior lip of cervix | Strain measurements using TDI-Q software | Strain ratio (endo/midcx) between preterm and term delivery groups | Strain ratio R selective was identified as the best predictor of sPTD |
| 2014 | Wozniak et al.26 | Prospective observational study | Low-risk (18–22 wk) | 333 | 45 (8.2) | Samsung Medison V20 | Internal (patients' breathing, arterial pulsation) | IOS | Subjective IOS color assessment: red (soft), yellow (medium soft), blue (medium hard), purple (hard) | Frequency of preterm deliveries in various categories of IOS assessment | sPTD < 37 weeks were higher in the red and yellow groups |
| 2015 | Hernandez-Andrade et al.16 | Cross-sectional study | Low-risk (11–28 wk) | 566 | 35 (10.5) | Hitachi Hi Vision | External (manually) | Circular endocervical area in the IOS | The percentage of tissue displacement or deformation that resulted during the manual application of oscillatory pressure | IOS endocervical strain among sPTD ≤ 34, < 37 weeks, and term delivery groups | Strain in the 3rd and 4th quartiles in IOS has increased risk of sPTD ≤ 34, < 37 weeks |
| 2015 | Sabiani et al.22 | Prospective longitudinal study | Low-risk (exam in each trimester) | 72 | 9 (12.5) | Hitachi Hi Vision | External (manually) | 1 cm2 at anterior and posterior lip | EI = E ant. Lip/(E ant. Lip + E post. Lip) | Unfavorable outcome (PTD, PPROM, Em cerclage) between low and high EI groups | Low EI was associated with unfavorable outcomes |
| 2014 | Swiatkowska-Freund et al.24 | Not stated | High-risk (preterm uterine contractions at 22–36 wk) | 44 | 21 (47.7) | Samsung Medison V10 | Internal (patients' breathing, arterial pulsation) | A circle of 5 mm in diameter was placed in each of five regions | Elastography index, five-step (0–4) color scale in anterior.wall, posterior wall, IOS, EOS and cervical canal | Correlation between EI for different parts of the cx and risk of sPTD, and time from exam to delivery | Significant correlation between EI of IOS and time from exam to delivery and also risk of sPTD |
| 2015 | von Schöning et al.25 | Prospective cohort study | High-risk (preterm labor at 23–34 wk) | 64 | 25 (39.1) | Hitachi Hi Vision Preirus | No additional pressure | Rectangular ROI including the cervix and cervical canal | Color scale: blue (stiff), green (average), red (deformable) | Correlation between stiff tissue and preterm birth | The mean proportion of the blue area correlated significantly with preterm birth |
| 2015 | Woźniak et al.27 | Prospective observational study | High-risk (CL ≤ 25 mm at 18–22 wk) | 109 | 45 (41.3) | Samsung Medison V20 | Internal (patients' breathing, arterial pulsation) | IOS | Subjective IOS color assessment: red (soft), yellow (medium soft), blue (medium hard), purple (hard) | Percentage of PTDs in various categories of elastographic cervical assessment | The number of PTDs was significantly higher in the red group, than in the blue and purple groups |
| 2015 | Muller et al.19 | Cross-sectional study | High-risk (preterm uterine contraction at 24–35 wk)/control group | 81/110 | 10 (12)/5 (4.3) | Aixplorer SuperSonic Imagine | Acoustic radiation force impulse (shear wave) | A circle of 8 mm in diameter was placed in lower anterior part of the cervix | Shear wave speed | Shear wave speed in preterm labor or preterm birth (compared to control) | Shear wave speed was significantly reduced in patients diagnosed with pre-term labor and in patients who actually delivered preterm. |
| 2018 | Agarwal et al.14 | Prospective observational study | High-risk (preterm uterine contractions at 28–37 wk) | 34 | 14 (41.2) | Siemens Healthcare Acuson S2000 | Acoustic radiation force impulse (shear wave) | Rectangular ROI (10 × 6mm sized) was placed on the anterior wall of the internal os | 5 color EI and shear wave velocity | EI and shear wave speed between preterm and term birth group | Significant higher EI and lower shear wave speed was observed in preterm birth compared to term birth group |
Data are presented as number (%).
sPTD = spontaneous preterm delivery, ROI = region of interest, IOS = internal os, EI = elastography index, EOS = external os of cervix, EI = elasticity index, PTD = preterm delivery.