A Guide to Internal Fetal Monitoring

Device Monitors Heart Rate in High-Risks Pregnancies

Woman with a drawing of a baby
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Internal fetal monitoring involves the placement of an electrode directly onto the scalp of the baby while it is still in the womb. This test is performed to evaluate the baby's heart rate as well as the variability of heart beats at the time of labor.

While IFM is most often used during high-risk births, it can also be used in a low-risk birth if the care team is unable to get an accurate reading from external monitoring techniques, such as auscultation and electronic fetal monitor (EFM).

How Internal Fetal Monitoring Is Performed

The IFM is inserted through the cervix to the part of the baby's body closest to the opening (typically the scalp). If the mother has not broken her water, an amniotomy will be performed to do so. A fetal electrode will then be placed by screwing a tiny wire into the top layers of the baby's scalp.

At the same time, an intrauterine pressure catheter (IUPC) can also be placed inside the uterus between the uterine wall and the baby. This also allows the birth team to measure the exact force of the mother's contractions rather than relying on the less accurate forms of external monitoring. This is especially useful when an induced labor is indicated.

Advantages of Internal Fetal Monitoring

Internal fetal monitoring allows for direct monitoring of the baby's heart as opposed to an auscultation which is an indirect form of monitoring. Auscultation employs the use of a device that listens through the woman's stomach, either in the form of a stethoscope or an ultrasound fetoscope.

Auscultation is the most common technique used for low-risk pregnancies.

IFM also overcomes one of the major limitations of the EFM: the need for the woman to remain absolutely still. With an EFM, the monitoring device is strapped around the woman's waist. Any movement can disrupt the signal and suggest irregularities which may or may not be there.

Internal monitoring may also prevent an unnecessary cesarean if fetal distress is indicated on external monitoring but not the IFM.

Risks of Internal Fetal Monitoring

Despite its advantages, there are a number of risks associated with IFM, including:

  • bruising or scratching of the baby's scalp
  • the risk infection to the mother or baby from an outside source
  • the restriction of movement for the mother which can make labor more painful and difficult
  • the risk of infection from mother to child (IFM is contraindicated in women with HIV, herpes, and hepatitis)

The IFM procedure itself has attracted controversy among some practitioners who believe it is unnecessarily invasive. Some studies have suggested that its use is associated with higher, rather than lower, rates of cesarean births and forceps delivery.

One study conducted in 2013 reported that, of 3,944 women in whom IFM was used, 18.6 percent ended up getting a cesarean versus 9.7 percent who didn't have an IFM. The rates of fever in women was also nearly three times higher (11.7 percent versus 4.5 percent).

No differences in the health were seen in babies exposed to IFM compared to those who were not.

Source

  • Harper, L.; Shanks, A.; Tuuli, M.; et al. "The Risks and Benefits of Internal Monitors in Laboring Patients." Am J Obstet Gynecol. 2013; 209(1): 38.e1-38.e6.

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