NEW ORLEANS – Maternal obesity does not lessen the predictive value of noninvasive uterine electromyography monitoring, according to a poster presentation at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.
"We wanted to see if in this subset of pregnant women, the noninvasive method was as effective as in other pregnant women," said Dr. Miha Lucovnik, a perinatologist at the University Medical Center, Ljubljana, Slovenia.
"Uterine contractions, at term or preterm, are one of the most common reasons for visits to obstetrical triage, but determining which patient with contractions is in true labor and needs to be admitted is, however, difficult," said Dr. Lucovnik. "The inability to accurately diagnose preterm labor leads to missed opportunities to improve outcomes of premature neonates, and also to unnecessary costs and side effects of treatments in women who would not deliver preterm regardless of intervention."
Dr. Miha Lucovnik
One of the more common monitoring methods – tocodynamometry – measures length and frequency of contractions but is often ineffective at detecting these signals in women with a BMI of 30 kg/m2 and above, he said.
Electromyography (EMG) is more effective at monitoring the progression of true labor, because it can detect "the changes in cell excitability and coupling necessary for effective contractions," said Dr. Lucovnik.
To detect uterine activity, electrodes are placed on the patient’s abdomen with vertical and horizontal axes parallel to the patient’s vertical and horizontal axes, respectively, and with center-to-center distances between adjacent electrodes set about 5.0-5.5 cm apart. The uterine EMG is then measured for 30 minutes.
For the study, Dr. Lucovnik and his colleagues reviewed the predictive values of uterine EMG for preterm delivery in 88 women divided into three cohorts: 20 with a BMI of 30 or greater; 64 with a BMI of 25-29.9; and 4 with a BMI of 18.5-24.9.
The investigators did not find any significant difference between the cohorts in the area under the curve prediction of preterm delivery within 7 days (AUC was 0.95 in the normal and overweight cohorts, and 1 in the obese group; P = .08).
Six patients with low uterine EMG scores delivered prematurely within 7 days from the EMG measurement. No significant differences in BMI were reported between this false negative group (range, 26.13 plus or minus 1.03) and the combined true positive and true negative preterm labor groups (range, 28.04 plus or minus 3.77; P = .32).
"We know that predictive values of currently used methods to diagnose preterm labor are even lower in women with high BMI," said Dr. Lucovnik. "Our study showed that the accuracy of uterine EMG monitoring and its predictive value for preterm delivery are not affected by obesity in pregnant patients."
Dr. Lucovnik reported that he did not have any relevant disclosures.