Internal Fetal Monitoring (IFM) is a specialized technique used during labor to obtain a highly accurate and continuous measurement of the fetal heart rate and rhythm. This method involves placing a small electrode directly onto the baby’s presenting part, typically the scalp, while the baby is still inside the uterus. IFM provides a direct electrical signal from the fetal heart, which is significantly more reliable than external methods. External monitors, which use transducers placed on the mother’s abdomen, can frequently lose the signal due to maternal or fetal movement or maternal body mass. The internal approach bypasses these limitations to ensure uninterrupted data collection.
When Is Internal Fetal Monitoring Used
The decision to switch from external to internal monitoring occurs when the external reading is no longer providing clear or reassuring information about the baby’s well-being. A primary indication is a non-reassuring or ambiguous fetal heart rate tracing showing decreased variability or concerning patterns. In these situations, the direct measurement from the internal monitor can confirm or rule out true fetal distress, helping to avoid unnecessary interventions.
External monitoring can also be hampered by maternal body habitus, such as a high Body Mass Index (BMI), which interferes with the transmission of the heart rate signal. When the quality of the external tracing is poor and cannot be corrected, the accurate internal method becomes necessary. Internal monitoring also allows for the concurrent use of an Intrauterine Pressure Catheter (IUPC) to precisely measure the strength and duration of uterine contractions. This simultaneous, precise data on both fetal response and uterine activity is often needed for managing high-risk pregnancies.
Step-by-Step Guide to Attachment
Before the internal monitor can be attached, two physical conditions must be met to ensure safe access and placement. First, the amniotic sac must be ruptured, as the device must pass through the cervix and make direct contact with the baby. Second, the cervix must be dilated to an adequate extent, typically a few centimeters, to allow the passage of the electrode and its insertion guide.
The device used is called a Fetal Scalp Electrode (FSE), which is a thin wire electrode with a tiny spiral hook at the tip. The FSE is threaded through a hollow guide tube, which the healthcare provider inserts through the mother’s vagina and cervix. Once the guide tube is positioned against the baby’s presenting part, most often the scalp, the electrode is partially advanced.
To secure the electrode, the provider gently pushes and rotates the guide tube, causing the spiral tip of the electrode to thread into the outermost layer of the baby’s scalp skin. This twisting motion anchors the electrode firmly enough to maintain continuous electrical contact. The guide tube is then withdrawn, leaving the electrode wire secured to the scalp, with the wire extending out of the mother’s vagina. This wire is finally connected to a cable, which transmits the electrical signals to the external monitoring machine for constant display and recording of the fetal heart rate.
Understanding Potential Risks and Removal
While internal monitoring is highly effective, it is an invasive procedure that carries a few potential risks. The most common complication is minor physical trauma to the fetal scalp at the site of attachment, such as a small puncture mark, bruising, or a minor laceration. These minor injuries typically heal quickly after birth.
A less common, but more serious, risk is the transmission of infection, particularly if the mother has active infections like HIV or Herpes Simplex Virus. The electrode creates a small break in the skin barrier, which very rarely can lead to a localized scalp infection or a scalp abscess in the newborn. Healthcare providers weigh these risks against the necessity of obtaining accurate heart rate data. The removal process is straightforward and is done either during the second stage of labor or immediately after the baby is delivered. The electrode cable is simply disconnected from the monitor and the wire is carefully untwisted and pulled away from the baby’s scalp.