Ultrasound Measurement of Fetal Adrenal Gland Better Predictor of Preterm Birth

Researchers have shown that measuring the fetal zone of the adrenal gland is a better predictor of preterm birth than measuring cervical length.

Researchers from the University of Maryland (College Park, USA) and Yale University (New Haven, CT, USA) have followed up on early research that they conducted using three-dimensional (3D) ultrasound techniques. They presented the study‘s findings in February 2010 at the Society for Maternal-Fetal Medicine's (SMFM) annual meeting, The Pregnancy Meeting, in Chicago, IL, USA. "We previously discovered that three-dimensional adrenal gland volume [AGV] is a very accurate predictor of preterm birth,” said Dr. Ozhan Turan, the study's author. "However, most people around the world don't have access to that technology; therefore, we have created measurements that can be done with 2D ultrasound that are very effective to predict preterm birth.”

In the study, patients presenting with preterm labor symptoms had ultrasound measurement of the cervical length (CL) and fetal adrenal gland dimension. Using 3D ultrasound with VOCAL cAGV (AGV [adrenal gland volume]/estimated fetal weight), 2D depth of the whole-gland (D), and fetal zone (d) were measured. The d/D ratio was calculated as an index of FZE (fetal zone estimation). The cAGV, d/D, and CL were compared for prediction of preterm birth within seven days.

Sixty-two singletons with preterm labor at 23-37 weeks' gestation were evaluated. Measurement-to-delivery interval only correlated with cAGV and d/D (r = -0.32; p = 0.011 and r = -0.47; p = 0.001, respectively) but not CL (p = 0.83). Twenty women had preterm birth at less than seven days (group A) while 42 (group B) delivered in seven days or more from initial assessment. While CL was similar (p = 0.5), cAGV and d/D were higher in group A (p < 0.0001 for both). ROC area under the curve was significantly greater for cAGV and d/D than for CL (0.82, 0.91, and 0.59; p < 0.01 and 0.001, respectively) without any significant differences between adrenal gland measurements. Using receiver operator curve (ROC)-derived cutoffs for preterm birth in less than seven days was best predicted by d/D and cAGV but not CL.

"Prior to this we haven't had a good method to predict who will present with preterm labor,” concluded Dr. Turan. "Measuring the cervical length leads to a high percentage of false positives and also it has limited sensitivity. Hopefully, if adopted, this method will allow for an easy, inexpensive way to identify real preterm deliveries. Therefore, we will be better managing these pregnancies.”

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