Objective: To develop a nonpenetrating scalp electrode for intrapartum fetal monitoring.
Design: Preliminary observational evaluation of the device.
Setting: An urban academic hospital in Johannesburg, South Africa.
Subjects: Fifteen women in labour.
Intervention: Application of the electrode for intrapartum monitoring.
Outcome measures: Quality of tracings, duration of application, disconnection of the electrode, marking of the scalp.
Results: Application was successful in 13 of 15 women, and high quality tracings obtained in 12.
Conclusions: The design of scalp electrode tested is effective and produces high quality tracings in most cases.
PIP: The fetal scalp electrodes currently used to obtain fetal heart rate (FHR) recordings during labor employ single or double curved needles which penetrates the fetal skin to obtain a purchase and electrical contact. A nonpenetrating scalp electrode was designed whose application to the fetal scalp is maintained by means of suction. The nickel fetal plate of the electrode measures 16 mm in diameter and has multiple perforations to distribute the effect of the suction and maintain optimal electrical contact over its whole surface. The electrode has an overall diameter of 20 mm and can be applied to the presenting part from 2-3 cm cervical dilatation. Application of the electrode was attempted in 15 consecutive pregnancies. Of the 15 consecutive attempts, 13 were successful. Unsuccessful attempts were caused by a blocked suction tube following repeated resterilization and reuse of the electrode in one instance and failure to position the electrode correctly in an excessively anxious woman in another. The quality of FHR tracing in 12 was considered good, providing continuous recording with minimal interference, while, in 1 woman, the tracing was poor. Good quality tracings were obtained even when the electrode was applied over thick hair, in the presence of vernix caseosa, and, in 1 application, to the buttocks. In 9 applications, the tracing started immediately after application, and, in the rest, there was a lag period of 2-20 minutes before the tracing commenced. A subsequent modification to a more finely apertured stainless steel mesh electrode plate eliminated the problem of a lag phase. In 1 instance, the electrode was disconnected during examination; in 2 cases, it was detached 10 minutes and 1 minute before delivery, respectively; and, in 10 cases, it remained in place until delivery. Transient redness of the fetal scalp was noted in 6 babies, and, in 2 babies, fine vesicles were noticed which disappeared within 2-3 days. This problem may be avoidable by using less suction pressure.