New ultrasound technique shows potential for detecting preterm labour risk.


Premature births can mean low birth-weights and other medical problems for newborns, however, there are steps that doctors can take to reduce the chances of premature birth if early warning signs are detected.  Presently the tests for preterm labour risk are placental alpha microglobulin-1, fetal fibronectin testing and cervical length measurement via transvaginal ultrasound.  These new tests have been the speculation of many investigations, however, the PPV, or positive predictive value of the tests are 76%, 29%, and 30% for PAMG-1, fFN and CL, respectively.  Therefore, researchers are actively looking for a preterm test with raised accuracy.

Now, researchers from North Carolina State University, Institut Langevin and Paris-Descartes University have conducted a proof-of-concept study that raises the possibility of using ultrasound techniques to detect cervical stiffness changes that indicate an increased risk of preterm labour in pregnant women. The team state that while additional work needs to be done, it may ultimately give doctors a new tool for determining when to provide treatment that can prevent preterm birth.  The opensource study is published in the journal Ultrasound in Medicine and Biology.

Previous studies show that one of the early symptoms preterm labour is a softening of the cervix, traditionally this stiffness is assessed by manually palpating the cervix.  However, the lab state that this is a subjective measure and decided to try a technique called shear wave elastography (SWE), which was developed to assess tissue stiffness for cancer diagnosis. The team reasoned that if SWE worked for detecting changes in other body tissues, it may also work for detecting changes in the cervix.

The team explain that in SWE, stiffness is measured based on how fast a mechanical shear wave propagates through the tissue. The current study showed that if the wave was more than one meter per second below the baseline for a woman’s gestational age, or how far along she is in her pregnancy, the woman was more likely to have a preterm birth.

The current study took 157 SWE measurements of pregnant women who were already scheduled for ultrasounds. The researchers then followed each patient’s pregnancy.  The results showed that patients between 24 and 35 weeks pregnant who had below average cervical stiffness were at higher risk of going into preterm labour.

The lab state that their work is only a first step, however, the data findings show that the technique is reproducible and that changes in cervical stiffness can be measured via SWE.  However, the team note that a longitudinal study needs to be performed that follows patients throughout pregnancy.  They go on to add that this would give a better understanding of how cervical stiffness changes over the course of pregnancy and help determine which changes are likely indicative of early onset labour.

Source:  North Carolina State University

 

Elastography and B-mode images of the cervix in pregnant women. Left: Normal patient (32.6 wk gestational age). Stiffness: 1.8 ± 0.3 m/s. Right: PUA patient (32.7 wk gestational age). Stiffness: 1.4 ± 0.22 m/s. The ROIs are represented by the white circles.  Assessment of the Cervix in Pregnant Women Using Shear Wave Elastography: A Feasibility Study.  Tsatsaris et al 2015.

Elastography and B-mode images of the cervix in pregnant women. Left: Normal patient (32.6 wk gestational age). Stiffness: 1.8 ± 0.3 m/s. Right: PUA patient (32.7 wk gestational age). Stiffness: 1.4 ± 0.22 m/s. The ROIs are represented by the white circles. Assessment of the Cervix in Pregnant Women Using Shear Wave Elastography: A Feasibility Study. Tsatsaris et al 2015.

 

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