Research

Barbara McFarlin, PhD, CNM, RDMS, Funded Projects

In Vivo Quantitative Ultrasound Assessment of the Rat Cervix

Funding Source: National Institute of Nursing Research PILOT

Dates: 10/15/05 – 10/15/07

Co-Investigators: Rosemary White-Traut

Abstract: The incidence of preterm birth in the United States has risen 16% since 1990 (Hamilton, Martin, & Sutton, 2004). In Illinois , the incidence of preterm birth was 11.8% in 1992 and has increased to 12.6% in 2002. African-American women are particularly at risk with incidences of 17% compared to 11% in White women(Hamilton, Martin, & Sutton, 2004). In 2002, 19% of all live births to African-American women in Chicago were born preterm. Labor has two major phases: the long conditioning phase of cervical ripening (collagen remodeling), and the active phase of extensive uterine activity that results in cervical dilatation. The latter phase is probably irreversible (Caritis, 2005; Ingemarsson & Lamont, 2003; Pryde, Janeczek, & Mittendorf, 2004). Prevention programs and pharmacologic agents have focused on controlling the active phase of extensive uterine activity, rather than cervical ripening. Our preliminary research developed, tested and demonstrated the feasibility of a new ultrasound technique that detected cervical ripening in the rat ex vivo (after the rat is euthanized, the cervix is excised). The new ultrasound technique utilizes echoes from the quantified ultrasound backscattered signals to yield unique tissue microstructure characteristics that are related to the ultrasound scattering sources. Specifically, the processed data yields three quantified tissue-based parameters: scatterer diameter, scatterer acoustic concentration, and scatterer strength factor. Each of these parameters uniquely characterizes different aspects of tissue microstructure. The initial findings detected significant changes in the pregnant rat ex vivo, as the pregnancy progressed towards delivery, using a discriminant function model to predict group assignment for rats of known gestational age. To utilize this ultrasound technique in humans, it is essential that an in vivo methodology be developed. The goal of this research is to provide pilot data to demonstrate that it is possible to obtain quantitative ultrasound and attenuation data with a 40-MHz miniature vaginal transducer on the rat in vivo (with the rat alive, under anesthesia). Once this study is completed and feasibility has been demonstrated, the goal is to apply for an NIH RO1 grant to study a larger sample of rats in vivo with transducers at 10, 20, 30, and 40-MHz, in preparation for human studies. Thus, the long-term goal of my research program is to develop a non-invasive ultrasound method to quantify cervical ripening in women and to identify initiation of preterm labor prior to the irreversible active phase, so that interventions can be developed to reduce the incidence of preterm birth.