Cervical stiffness evaluated in vivo by endoflip in pregnant women.

To determine the stiffness of the pregnant uterine cervix in vivo.Five women in early pregnancy and six women in late pregnancy were included. The EndoFlip is a 1-m-long probe with a 12-cm-long bag mounted on the tip. The tip of the probe was inserted into the cervical canal. Sensors spaced at 0.5-cm intervals along the probe were used to determine 16 serial cross-sectional areas of the bag. The diameter of the cervical canal could thereby be determined during inflation with up to 50 ml saline solution. Tissue stiffness was calculated from the geometric profiles and the pressure-strain elastic modulus (EP) at each sensor site. Three parts of the cervix were defined: the uterus-near part, the middle and the vaginal part. The EPmax was defined as the highest EP detected along the cervical canal.The EPmax was always found in the middle part of the cervix. The median EPmax was 243 kPa (IQR, 67-422 kPa) for the early pregnant women and 5 kPa (IQR, 4-15 kPa) for those at term. In the early pregnant women the stiffness differed along the cervical length (p<0.05) whereas difference along the cervix was not found for late pregnant women. A positive correlation coefficient (Spearman's rho) was established between the EPs of the uterus-near and the middle part (0.84), between the vaginal and the middle part (0.81), and between the uterus-near and the vaginal part (0.85).This new method can estimate the stiffness along the cervical canal in vivo. This method may be useful in the clinical examination of the biomechanical properties of the uterine cervix

The pressure-strain elastic modulus (EP) for the uterine-near part, the middle part and the vaginal part of the uterine cervix.

<p>Significant difference (one-way ANOVA) was found when comparing the three cervical parts for the early-pregnant women (p = 0.04) whereas axial variation was not found for the term-pregnant women (p = 0.88).</p

Box-plots showing the pressure-strain elastic modulus of the uterine-near part, the middle part and the vaginal part of the uterine cervix for early and term-pregnant women.

<p>The plus whiskers display the upper values within 1.5 times the interquartile range beyond 75th percentile and the minus whiskers, display the minimum value. Difference in EP along the length of the cervix was found for the early-pregnant women.</p

The averaged pressure-diameter curves for early-pregnant (solid lines) and term-pregnant women (dashed lines).

<p>The averaged pressure-diameter curves for early-pregnant (solid lines) and term-pregnant women (dashed lines).</p

Illustration of the probe in the uterine cervical canal.

<p>The tip of the probe is placed in the uterine cavity, with the middle two thirds of the probe in the cervical canal leaving 2–3 sensors visible outside the canal protruding into the vagina. The two gray lines represent the excitation electrodes whereas the 16 black sensors detect 16 cross-sectional areas along the probe.</p

Validation data from testing in two phantoms.

<p>Each colored line represents the diameter data obtained from each sensor. The bag was inflated and deflated several times in a cylinder-shaped phantom with the diameter 20.8 mm (A) and in a funnel-shaped phantom with diameters ranging from 5–19 mm (B). The tracings demonstrate that the diameter measurements are accurate and reproducible.</p

Geometric and biomechanical properties of the uterine cervix of an early-pregnant woman (left column, A–D) and term-pregnant woman with an unripe cervix (right column E–H).

<p>A and E) Spatio-temporal diameter plots. The black line illustrates the volume of the bag (ml), the white line the pressure inside the bag (mmHg), and the colors spanning from blue to red illustrate the magnitude of diameters obtained in the measurement area. B and F) The cervical canal configuration generated at distension volume 2 ml (blue line) and 45 ml (red line). The black dots represent the internal and external cervical os of the uterine cervix. C and G) Pressure-diameter plot. The pressure-diameter relationship for three locations representing the uterus-near part (blue line), the middle part (red line), and the vaginal part (green line) of the uterine cervix. The black dots represent the linear part of the curve. D and H) Pressure-strain elastic modulus plot. The pressure-strain elastic modulus distribution along the cervical canal.</p