Fetal Bradycardia (Cord Prolapse) Case File

Fetal Bradycardia (Cord Prolapse) Case File

Eugene C. Toy, MD, Patti Jayne Ross, MD, Benton Baker III, MD, John C. Jennings, MD

CASE 5

A 22-year-old G3P2 woman at 40 weeks’ gestation complains of strong uterine contractions. She denies leakage of fluid per vagina. She denies medical illnesses. Her antenatal history is unremarkable. On examination, the blood pressure (BP) is 120/80 mm Hg, heart rate (HR) is 85 beats per minute (bpm), and temperature is 98°F (36.6°C). The fetal heart rate is in the 140 to 150 bpm range. The cervix is dilated at 5 cm and the vertex is at –3 station. Upon artificial rupture of membranes, fetal bradycardia to the 70 to 80 bpm range is noted for 3 minutes without recovery.

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ANSWER TO CASE 5:

Fetal Bradycardia (Cord Prolapse)                                                   

Summary: A 22-year-old G3P2 woman at term is in labor with a cervical dilation of 5 cm; the vertex is at – 3 station. Upon artificial rupture of membranes, persistent fetal bradycardia to the 70 to 80 bpm range is noted for 3 minutes.

Next step: Vaginal examination to assess for umbilical cord prolapse.

ANALYSIS

Objectives

1. Understand that the first step in the evaluation of fetal bradycardia in the face of rupture of membranes should be to rule out umbilical cord prolapse.
2. Understand that the treatment for cord prolapse is emergent cesarean delivery.
3. Know that an unengaged presenting part, or a transverse fetal lies with rupture of membranes, predisposes to cord prolapse.

Considerations

This patient has had two prior deliveries. She is currently in labor and her cervix is 5 cm dilated. The fetal vertex is at – 3 station, indicating that the fetal head is unengaged. With artificial rupture of membranes, fetal bradycardia is noted. This situation is very typical for a cord prolapse, where the umbilical cord protrudes through the cervical os. Usually, the fetal head will fill the pelvis and prevent the cord from prolapsing. However, with an unengaged fetal presentation, such as in this case, umbilical cord accidents are more likely. Thus, as a general rule, artificial rupture of membranes should be avoided with an unengaged fetal part. Situations such as a transverse fetal lie or a footling breech presentation are also predisposing conditions. It is not uncommon for a multiparous patient to have an unengaged fetal head during early labor. The lesson in this case is not to rupture membranes with an unengaged fetal presentation. With fetal bradycardia, the next step would be a digital examination of the vagina to assess for the umbilical cord, which would feel like a rope-like structure through the cervical os. If the umbilical cord is palpated and the diagnosis of cord prolapse confirmed, the patient should be taken for immediate cesarean delivery. The physician should place the patient in Trendelenburg position (head down), and keep his or her hand in the vagina to elevate the presenting part, thus keeping pressure off the cord.

APPROACH TO:

Fetal Bradycardia                                                        

DEFINITIONS

ENGAGEMENT: Largest transverse (biparietal) diameter of the fetal head has negotiated the bony pelvic inlet.

FETAL BRADYCARDIA: Baseline fetal heart rate < 110 bpm for > 10 minutes.

UMBILICAL CORD PROLAPSE: Umbilical cord enters through the cervical os presenting in front of the presenting part.

ARTIFICIAL RUPTURE OF MEMBRANES: Maneuver used to cause a perforation in the fetal chorioamniotic membranes.

CLINICAL APPROACH

The onset of fetal bradycardia should be confirmed either by internal fetal scalp electrode or ultrasound, and distinguished from the maternal pulse rate. The initial steps should be directed at improving maternal oxygenation and delivery of cardiac output to the uterus. These maneuvers include (1) placement of the patient on her side to move the uterus from the great vessels, thus improving blood return to the heart, (2) intravenous (IV) fluid bolus if the patient is possibly volume depleted, (3) administration of 100% oxygen by face mask, and (4) stopping oxytocin if it is being given (Table 5– 1).

Simultaneously with these maneuvers, the practitioner should try to identify the cause of the bradycardia, such as hyperstimulation with oxytocin. With this process, the uterus will be tetanic, or the uterine contractions will be frequent (every 1 minute); often a β-agonist, such as terbutaline, given intravenously will be helpful to relax the uterine musculature. Hypotension due to an epidural catheter is another common cause. Intravenous hydration is the first remedy, and if unsuccessful, then support of the blood pressure with ephedrine, a pressor agent, is often useful. A vaginal examination, when the membranes are ruptured, is “a must” to identify overt umbilical cord prolapse. A rope-like cord will be palpated, often with pulsations (Figure 5– 1). The best treatment is elevation of the presenting part digitally and emergent cesarean delivery. In women with prior cesarean delivery, uterine rupture may manifest as fetal bradycardia.

Table 5–1 • STEPS TO TAKE WITH FETAL BRADYCARDIA

Confirm fetal heart rate (vs maternal heart rate) Vaginal examination to assess for cord prolapse Positional changes Oxygen Intravenous fluid bolus and pressors if hypotension persists Discontinue oxytocin, consider beta-agonist if tachysystole

Figure 5–1. Umbilical cord prolapse. A footling breech presentation predisposes to umbilical cord prolapse.

FETAL HEART RATE ASSESSMENT

The baseline fetal heart rate is normally between 110 and 160 bpm, with fetal bradycardia <110 bpm and tachycardia >160 bpm. The fetal heart rate typically has moderate variability, whereas diminished variability may be caused by sedating medications or more rarely fetal acidosis. Accelerations are abrupt increases in fetal heart rate of at least 15 bpm lasting for 15 seconds, and typically are indicative of adequate fetal oxygenation. Decelerations may be early, late, or variable depending on its configuration and timing with the uterine contraction.

CASE CORRELATION See also Case 1, Normal Labor and Decelerations to review definitions of bradycardia, and types of decelerations.

COMPREHENSION QUESTIONS

5.1 An 18-year-old woman, who had undergone a previous low-transverse cesarean delivery, is admitted for active labor. During labor, an intrauterine pressure catheter displays normal uterine contractions every 3 minutes with intensity up to 60 mm Hg. Fetal bradycardia ensues. Which of the following statements is most accurate?

A. The normal intrauterine pressure catheter display makes uterine rupture unlikely.

B. The most common sign of uterine rupture is a fetal heart rate abnormality.

C. If the patient has a uterine rupture, the practitioner should wait to see whether the heart tones return to decide on route of delivery.

D. The intrauterine pressure catheter has been found to be helpful in preventing uterine rupture.

5.2 A 32-year-old G1P0 woman is at 42 weeks’ gestation and being induced for post-term pregnancy. She has had an uncomplicated prenatal course. Her BP is 100/ 60 mm Hg. The fundal height is 40 cm. Her cervix is closed, 3 cm long, and firm on consistency. The obstetrician decides on using a cervical ripening agent with misoprostol in the vagina. Approximately 2 hours after placing the misoprostol, the patient has an episode of fetal prolonged deceleration to 80 bpm for 6 minutes. Which of the following is the most likely etiology of the prolonged deceleration?

A. Placental abruption

B. Sepsis

C. Umbilical cord prolapse

D. Uterine hyperstimulation

5.3 A 28-year-old G1P0 woman at 35 weeks’ gestation is in the obstetrical (OB) triage area with spontaneous rupture of membranes. The fetal heart rate baseline is 150 bpm with normal variability. There are accelerations seen, and numerous late decelerations noted. In an effort to improve oxygenation to the fetus, which of the following maneuvers would most likely help in this circumstance?

A. Supine position

B. Epidural anesthesia

C. Morphine sulfate

D. Stop the oxytocin

5.4 A 33-year-old G2P1 woman at 39 weeks’ gestation in active labor is noted to have a 10-minute episode of bradycardia on the external fetal heart rate tracing in the range of 100 bpm, which has not resolved. Her cervix is closed. Which of the following is the best initial step in management of this patient?

A. Fetal scalp pH assessment

B. Emergency cesarean delivery

C. Intravenous atropine

D. Intravenous terbutaline

E. Assess maternal pulse

5.5 A 25-year-old G1P0 woman at 38 weeks’ gestation is in active labor. The patient is noted to be 5 cm dilated/ 100% effaced/ – 1 station. She is in severe pain. She received meperidine intravenously and after an hour, her pain is still severe. The patient has an epidural catheter for pain control. Her BP is 90/ 50 mm Hg and HR is 90 bpm. The fetal heart rate reveals a baseline of 140 bpm with persistent late decelerations. Which of the following is the best next step in managing this patient?

A. Emergency cesarean

B. Ephedrine intravenously

C. Naloxone intravenously

D. Transfusion with packed erythrocytes

ANSWERS

5.1 B. The most common finding in a uterine rupture is a fetal heart rate abnormality, such as fetal bradycardia, deep variable decelerations, or late decelerations. The intrauterine pressure catheter has not been found to be helpful and sometimes confuses the picture and may delay the diagnosis of uterine rupture. Immediate cesarean section is indicated for suspected uterine rupture.

5.2 D. Prolonged fetal decelerations or fetal bradycardia associated with misoprostol cervical ripening is typically associated with uterine hyperstimulation, defined as greater than five uterine contractions in a 10-minute window. Although any of the prostaglandin cervical ripening agents may induce uterine hyperstimulation, misoprostol generally is associated with a higher risk. Its benefit is the very low cost.

5.3 D. The supine position causes uterine compression on the vena cava, which decreases the venous return of blood to the heart, leading to supine hypotension. One important maneuver when encountering fetal heart rate abnormalities is a positional change, such as the lateral decubitus position. Oxytocin and epidural anesthesia both can decrease oxygen delivery to the placental bed. Oxytocin may hyperstimulate the uterus and cause frequent contractions; this then results in frequent vasoconstriction of the uterine vessels which decreases the amount of blood arriving to the placenta and fetus over time. Thus, stopping the oxytocin may help improve oxygenation. An epidural can cause hypotension in the mother which may then lead to fetal bradycardia by also decreasing the amount of blood profusing the fetus per given time. Morphine sulfate can cause respiratory depression in the fetus, so it would not be a method of choice for increasing delivery of oxygen to the fetus.

5.4 E. The first step in the assessment of apparent fetal bradycardia is differentiating the fetal heart rate from the maternal pulse. This may be done with the use of a fetal scalp electrode or ultrasound. A fetal scalp pH is a maneuver to assess whether or not the fetus is receiving sufficient oxygen during labor, but cannot be done with a closed cervix. It requires at least 4-cm dilation to get a sample of blood from the fetal scalp. It is rarely performed today. If fetal bradycardia is confirmed, various maneuvers may be implemented to improve maternal oxygenation (placement of mother on her left side, IV fluid bolus, 100% O2 face mask, and stopping oxytocin). Simultaneously, IV terbutaline may be given to help relax the uterine musculature in an effort to increase blood flow and O2 supply to the fetus. If none of these methods work, a vaginal examination may reveal a cord prolapse, in this case the best treatment is elevation of the presenting part digitally and emergent cesarean delivery. Atropine may be used in a nonpregnant patient to treat bradycardia or arrhythmias, but is not indicated for fetal bradycardia.

5.5 B. This patient likely has late decelerations because of hypotension caused by the epidural. Sympathetic blockade from the epidural leads to vasodilation. The first treatment is intravenous fluids, and if the hypotension and/ or late decelerations are persistent, then a vasopressive agent such as ephedrine is used. Meperidine (Demerol) is associated with decreased fetal heart rate variability but not hypotension. Cesarean may be required if the fetal heart rate tracing does not improve, but typically epidural-induced hypotension will respond to therapy.

    CLINICAL PEARLS    

» The first steps in assessing fetal bradycardia after artificial rupture of membranes are distinguishing the heart rate from the maternal pulse rate and examining the vagina to assess for cord prolapse. » The best therapy for umbilical cord prolapse is elevation of the presenting part and emergency cesarean delivery. » The risk of cord prolapse with a vertex presentation or frank breech presentation is very low; the risk with a footling breech or transverse lie is substantially higher. » The most common finding with uterine rupture is a fetal heart rate abnormality such as deep variable decelerations or bradycardia. » The best treatment for suspected uterine rupture is immediate cesarean delivery.

REFERENCES

American College of Obstetricians and Gynecologists. Management of intrapartum fetal heart rate tracings. ACOG Practice Bulletin 116. Washington, DC; 2010. 

Bayshore RA, Koos BJ. Fetal surveillance during labor. In: Hacker NF, Gambone JC, Hobel CJ, eds. Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: Saunders; 2009:119-127. 

Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap LC III, Wenstrom KD. Intrapartum assessment. In: Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010:447-456.

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