WASHINGTON — Women who were able to bite down on a mouth guard had a significantly shorter second stage of labor, compared with women who didn't use a mouth guard, based on the results of a randomized trial of 64 women with uncomplicated singleton pregnancies.
Developing a way to help women push harder may shorten the second stage of labor and reduce the number of cesarean or instrumental deliveries that are associated with a longer second stage, Dr. Janna Mudd said at the annual meeting of the Society of Obstetric Anesthesia and Perinatology.
“We wanted to come up with a method that would maximize maternal expulsive effort,” she explained.
Previous studies have shown that wearing a mouth guard increases the isometric strength of different muscle groups, and the researchers hypothesized that the device (a plastic mouth guard similar to those used in sports) would encourage women to push harder during the second stage of labor.
To test this theory, Dr. Mudd and her colleagues at the University of Maryland in Baltimore randomized women at a single hospital in Baltimore to wear or not wear a mouth guard during the second stage of labor. The women were nulliparous with uncomplicated singleton term pregnancies, and an average gestational age of 39 weeks. There were no significant obstetrical demographic differences between the two groups, Dr. Mudd commented.
The researchers excluded women with diabetes, preeclampsia, or other comorbidities; those whose babies were large for gestational age; or those who had shoulder dystocia or other potential complications. A total of 38 women (19 in each group) were evaluated during the second stage of labor. Overall, the average duration of the second stage was 19 minutes in the mouth guard group vs. 31 minutes in the control group.
Each of the women in the study had received an epidural, and their pushing was directed by a doctor or midwife. The women were instructed to start pushing when they were deemed fully dilated based on a digital exam.
There were no significant differences in birth weight, head circumference, Apgar scores, umbilical arterial and venous pH, and rate of NICU admission among infants of women who used the mouth guards, compared with those women who did not wear a mouth guard.
“We also were very interested in patient satisfaction,” Dr. Mudd said. “I was surprised how many people seemed very enthusiastic and willing to try anything to avoid an operative deliver,”
Overall, the patients were very satisfied with the device and said they thought that wearing it helped them to focus while pushing, although some women reported discomfort and nausea while using the mouth guard. On average, the women who used the mouth guards rated their satisfaction as 4 on a scale of 1–5.
The researchers considered three possible mechanisms of action for the impact of a mouth guard on the second stage of labor: a direct effect on the muscles, a secondary effect on posture, and increased endurance during isometric muscle activity.
In response to a question from the audience, Dr. Mudd noted that she had no explanation for why the second stage of labor in the study population as a whole was shorter than average for nulliparous women. (The American Pregnancy Association says the second stage lasts anywhere from approximately 20 minutes to 2 hours.)
The study was limited by its small size, and more research is needed to confirm the results, Dr. Mudd said. Factors to consider in future studies include measuring the uterine pressure to identify whether the expulsive effort is greater in women who wear mouth guards during the second stage of labor, she commented.
The researchers had no financial conflicts to disclose related to the study.