SAN DIEGO – An investigational system that provides precise measurement and real-time maternal feedback of descent during the second stage of labor shortened the second stage in pregnant women who received epidural anesthesia, a randomized, controlled study demonstrated.
The system also reduced composite adverse maternal outcomes and reduced neonatal ICU admissions, Dr. Merlin B. Fausett reported at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.
“The length of second-stage labor is highly correlated with the incidence of maternal morbidities and the incidence of neonatal ICU admissions,” said Dr. Fausett, a maternal-fetal medicine specialist in Missoula, Montana. “The majority of laboring women in the U.S. have epidurals during labor for labor pain management. In some studies, the length of second-stage labor is increased in women receiving regional anesthesia, compared with women without. This increased length of labor may be due to the lack of maternal sensation, resulting in decreased physiologic feedback that inhibits learning and decreases the efficacy of maternal expulsive efforts.”
Recognizing the difficulties with a long second stage of labor, clinicians have developed several nonoperative methods of attempting to reduce its length, including coached pushing, allowing periods of passive descent, and waiting for the laboring women to develop an urge to push. Some physicians also provide maternal visual feedback with a mirror.
“These methods have proven to be of limited benefit at best,” Dr. Fausett said. “With coached pushing, for example, frequent or continuous vaginal examinations may cause genital trauma, perinatal edema, and increased rates of infection. This method also requires a significant amount of the provider’s time. Finally, the use of mirrors is not well accepted by many patients and is only effective if the baby is already low enough in the pelvis to be visible to the mother with the mirror.”
Dr. Fausett and his colleagues hypothesized that using an experimental metrology device and software to give real-time quantitative maternal feedback of fetal descent during labor could result in more effective expulsion efforts, reduce the length of second stage, and improve perinatal outcomes.
They designed a prospective randomized, nonblinded trial to assess the clinical impact of providing laboring women real-time audiovisual feedback regarding fetal descent during second stage. The primary outcomes were a comparison of the length of time from initiation of pushing until delivery of the baby and a comparison of a composite of clinical outcomes.
“The pushing time comparison was to be made between study and control group subjects who had a spontaneous vaginal delivery, thus excluding those whose second stage was short with an operational or cesarean delivery,” Dr. Fausett said. “This comparison was also to control for fetal station at the initiation of pushing, as well as neonatal birth weight.”
The composite outcome was defined as a comparison of the number of women in the study versus control group who had any one of the following outcomes: cesarean delivery, operative vaginal delivery, third- or fourth-degree lacerations, an intra-amniotic infection, or NICU admission.
Developed by OB Technologies, the metrology device consisted of a support arm attached to the maternal sacral area using tape. This support arm extended through the gluteal cleft and terminated distal to the perineum. An optical sensor was then attached to the distal center of the support arm. A standard needle scalp electrode was modified by placing a semirigid wire at the base of the attachment where the spiral electrode attached to the needle head.
“This wire extended from the scalp across the optical sensor, and thus movement of the fetal head relative to the maternal pelvis was detected,” Dr. Fausett explained. “The instrument allowed detection of movements as small as 50 micrometers. Fetal station relative to the position in the pelvis was recorded. For feedback subjects, the movement was conveyed to them graphically and audibly using piano tones that occurred as often as every 150 milliseconds. The feedback was related to both the velocity and the distance of descent.”
Dr. Fausett reported results from 69 laboring nulliparous women with singleton pregnancies who were at least 36 weeks’ gestational age with epidural anesthesia.
Women in the study group received feedback on descent during the second stage by way of a laptop that displayed graphics and sounded musical notes corresponding to the movement of the fetus relative to the maternal bony pelvis.
Control subjects were not provided the visual and auditory feedback but the descent information was recorded with the same equipment. Normal labor and delivery procedures, including pelvic examination and nurse-provided feedback to the patient, were allowed in both groups. On postpartum day one, study subjects were asked to complete an anonymous survey about the use of the feedback device.