Fetal Timeline      Maternal Timeline      News     News Archive    Aug 19, 2015 

Ultrasound is routinely used to identify fetal growth inutero. A new study by North Carolina State University
finds the technique is successful in determining cervical softness which preceeds premature delivery.
Image Credit: Petr Kratochvil

Ultrasound has potential to detect preterm labor

A proof-of-concept study using ultrasound to detect changes in cervical stiffness, can indicate if there is risk for preterm labor. It may ultimately give doctors a new tool for preventing preterm birth.

Premature births can mean low birthweight and medical problems for newborns, but steps can be taken to reduce early deliveries if warning signs are detected. One early symptom is softening of the cervix. Traditionally, this stiffness is assessed by manually palpating the cervix. However, longterm experience by the doctor, as well as familiarity with individual patient changes in cervix softness over time, is needed for accuracy.

"This is a subjective measure, and we wanted to determine if ultrasound could be used to quantitatively assess how stiff the cervix is - and, by extension, whether a woman is at risk of going into labor prematurely," says Marie Muller, an assistant professor of mechanical engineering at North Carolina State University and lead author on the paper published in the journal Ultrasound in Medicine and Biology.

Muller and her colleagues decided to try a technique called shear wave elastography (SWE), which was developed to assess tissue stiffness for cancer diagnosis. They reasoned that if SWE worked for detecting changes in other body tissues, it may also work for detecting changes in the cervix.

Working with a maternity hospital in Paris, the researchers did SWE measurements of 157 pregnant women who were already scheduled for ultrasounds, then followed each patient's pregnancy.

They found that patients between 24 and 35 weeks pregnant who had below average cervical stiffness were at higher risk for preterm labor.

In SWE, stiffness is measured based on how fast a mechanical shear wave propagates through the tissue. What the researchers found was 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.

"This work is only a first step. We know the technique is reproducible. We know we can measure these changes in cervical stiffness. However, we need to do a longitudinal study that follows patients throughout pregnancy. That would give us a better understanding of how cervical stiffness changes over the course of pregnancy. This would help us determine which changes are likely indicative of early onset labor."

Marie Muller, Assistant Professor, Mechanical Engineering, North Carolina State University, and lead author on the paper

Abstract
The quantitative assessment of the cervix is crucial for the estimation of pre-term delivery risk and the prediction of the success of labor induction. We conducted a cross-sectional study using shear wave elastography based on the supersonic shear imaging technique. The shear wave speed (SWS) of the lower anterior part of the cervix was quantified over an 8-mm region of interest in 157 pregnant women. Cervical SWS is slightly but significantly reduced in patients diagnosed with pre-term labor and in patients who actually delivered pre-term.

The paper was co-authored by Dora Aït-Belkacem, Jean-Luc Gennisson, and Mickaël Tanter of Institut Langevin; Mahdieh Hessabi of Paris-Descartes University; Gilles Grangé, Edouard Lecarpentier, and Vassilis Tsatsaris of Paris-Descartes University and Premup Foundation; and François Goffinet of Paris-Descartes University, CIC Cochin-Necker and Premup Foundation.

The work was supported by LABEX WIFI (France's Laboratory of Excellence program) under grant number ANR-10-LABX-24.

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