Norm of Internal Fetal Monitoring
Fetal heart rate (FHR) and variability normal.
Maternal Contractions and Intrauterine Pressure During Labor:
|Prelabor||<3 contractions over 10 minutes|
|25–40 mm Hg contraction|
|First stage||pressure <6 contractions over 10 minutes|
|8–12 mm Hg baseline pressure|
|30–40 mm Hg contraction pressure|
|Second stage||1 contraction about every 2 minutes|
|10–20 mm Hg baseline pressure|
|50–80 mm Hg contraction pressure|
Usage of Internal Fetal Monitoring
Monitoring of beat-to-beat variability of FHR and rate and pressure monitoring of uterine contractions during labor. Often used as an adjunct to external fetal monitoring. More accurate than external fetal monitoring, especially in cases of maternal obesity. Internal monitoring is less affected by fetal or maternal movement than external monitoring.
Description of Internal Fetal Monitoring
During this invasive monitoring procedure, a sterile fetal scalp electrode and a uterine catheter are inserted through the vaginal canal for the purpose of FHR and uterine-contraction measurements during labor after 3-cm cervical dilatation and rupture of membranes. Internal monitoring is recommended over external monitoring for a better assessment of the effects of labor on the fetus and to provide interpretation of quality of contraction pattern.
Professional Considerations of Internal Fetal Monitoring
Consent form IS required.
Maternal uterine perforation; intrauterine infection; and fetal scalp infection, abscess, or hematoma.
Active genital herpes.
Test should be performed only when the fetal presenting part is the head.
- Obtain an antiseptic solution, sterile gloves, a fetal scalp electrode and guide, a pressure catheter for intrauterine contraction monitoring, a catheter guide, a transducer, a fetal heart monitor, and a topical antibiotic.
- Ascertain that membranes are ruptured and that the presenting part is the fetal head.
- The client is placed in a dorsal lithotomy position.
- The perineal area is cleansed with antiseptic solution.
- A sterile vaginal examination is performed to measure cervical dilatation and identify a fetal scalp location over bone for electrode placement.
- The electrode is guided through the vaginal canal and cervical os and gently screwed into place on the fetal scalp.
- The electrode wires are connected to the fetal monitor. Correct placement and functioning of the system are verified when a FHR signal is demonstrated by the fetal monitor.
- The pressure-sensitive catheter for monitoring uterine contractions is then guided into place, through the cervix, a shallow distance to the uterus. The distal end is connected to a pressure transducer for continuous monitoring of intrauterine pressure. The monitor is calibrated to zero for a uterine pressure baseline value.
- Continue monitoring FHR and contraction pattern as with external monitoring.
- Just before beginning the procedure, take a “time out” to verify the correct client, procedure, and site.
- Cleanse the fetal scalp electrode site with antiseptic at the time of delivery.
- Document observed laceration(s) of the baby's scalp.
Client and Family Teaching
- Explain procedure to client. Internal fetal monitoring poses risks (listed above) but provides much better assessment of how well the fetus is tolerating the labor process than external fetal monitoring does.
Factors That Affect Results
- Drugs that affect the sympathetic and parasympathetic nervous systems may influence FHR.
- The maternal position may cause fetal distress. The left side-lying position best promotes oxygen delivery to the fetus.
- The internal scalp electrode may be inserted and removed by a registered nurse who has received specialized preparation in this skill or by a physician. The intrauterine pressure catheter may be inserted only by a physician.