Ultrasound can identify risk of preterm birth early

Urbana, IL: A recent study has thrown light on the relevance of ultrasound for pregnancy and its use in predicting the risk of preterm births. This was reported based on the comparison of two sets of data derived from two separate ultrasound techniques to evaluate cervical changes. According to the researchers, both ultrasound techniques helped to estimate the attenuation coefficient of human cervical tissue and to thus assess the changes in it, providing a better picture of the true risk for preterm birth thereby.

The study was presented at the 178th Meeting of the Acoustical Society of America, held at the Hotel Del Coronado in San Diego. In the presentation, the researchers will discuss ultrasound techniques used during pregnancy.

Barbara L. McFarlin, UIC College of Nursing, Univ. of Illinois at Chicago, Chicago, IL, and colleagues looked at ultrasonic attenuation coefficients that can help scientists characterize cervical changes throughout pregnancy and prepare for birth before other symptoms such as the occurrence of dilations or contractions. They compared the spectral difference and spectral log difference techniques -- methods of finding the ultrasonic attenuation coefficient.

"Our research is based upon the biology of cervical changes in preparation for labor and childbirth, namely collagen remodeling. Ultrasonic attenuation is sensitive to these changes, as during pregnancy the collagen fibers are tightly packed and have high attenuation," said McFarlin. "In preparation for labor and birth, there is increased collagen disorganization, increased water content and inflammation of the cervix, with low ultrasonic attenuation."

After gathering data on the two ultrasound techniques, the authors identified which performed better when it came to detecting cervical changes.

"This ASA presentation primarily evaluates the agreement in attenuation coefficient estimates between the two spectral-based techniques without referring to clinical outcomes. Future research is needed to evaluate the two techniques in terms of the ability to improve clinical diagnostics," said another author of the study.

"More study will be needed to assess the performance of both techniques to find out which correlates well with the clinical picture so that their diagnostic value can be evaluated. This could eventually help doctors predict preterm birth and take preventive measures to delay birth if possible, or if required," concluded the authors.

Ultrasound in Pregnancy

In a pregnancy ultrasound, high-frequency sound waves (too high for the human ear to hear) are beamed at the uterus to reflect back in varying patterns, depending on the distribution of the tissues of the uterus and the baby. The reflected waves are collected by a receiver and analyzed by a software program to depict the image of the fetus, its heartbeat, its movements, and the surrounding uterus. This technique is used to pick up several complications that can occur in pregnancy.

Attenuation Coefficient

As ultrasound waves travel through tissue, they lose amplitude (size) and intensity (energy), and this change is called attenuation. If the distance through which they travel is fixed, waves at a higher frequency will be more affected or will weaken more, than those at a lower frequency. For this reason, lower frequencies are used to examine areas that are deeper in the body. This helps provide an image of these deeper structures, but the resolution will be less clear.

Abstract of the study, "Comparison of two spectral-based techniques for estimating the attenuation coefficient from human cervix," is published in the Journal of the Acoustical Society of America.

DOI: https://doi.org/10.1121/1.5136939