Decelerations

Decelerations during labor have different meaning depending on when they occur in relation to contractions.

Early Decelerations

Early decelerations are normal and due to head compression during contractions. The timing of onset, peak, and end coincides with the timing of the contraction. The degree of deceleration is proportional to the contraction strength. The effect is regulated by vagal nerve activation.

NO intervention necessary!!

Late Decelerations

Late decelerations are abnormal and are due to uteroplacental insufficiency (not enough blood) during contractions. They begin at the peak of contraction and end slowly after the contraction has stopped.

Intervention

■ Change maternal position to the lateral recumbent position.

■ Stop oxytocin (Pitocin) infusion.

■ Provide an IV fluid bolus.

■ Monitor maternal blood pressure.

■ If persist longer than 30 minutes, fetal scalp blood pH should be obtained and C-section considered.

Variable Decelerations

Variable decelerations are abnormal and can be mild or severe. They are due to cord compression and sometimes head compression. They can occur at any time. If they are repetitive, suspicion is high for the cord to be wrapped around the neck or under the arm of the fetus.

Intervention

■ Amnioinfusion: Infuse normal saline into the uterus through the in-trauterine pressure catheter to alleviate cord compression.

■ Change maternal position to side/Trendelenburg position.

■ Deliver fetus with forceps or C-section.

Fetal Tachycardia

Fetal tachycardia may indicate intrauterine infection, severe fetal hypoxia, congenital heart disease, or maternal fever.

Beat-to-Beat Variability (BTBV)

■ The single most important characteristic of the baseline FHR

■ Variation of successive beats in the FHR BTBV is controlled primarily by the autonomic nervous system, thus an important index of fetal central nervous system (CNS) integrity

■ At < 28 weeks' GA, the fetus is neurologically immature; thus, decreased variability is expected.

Short-Term Variability (STV)

■ Reflects instantaneous beat-to-beat (R wave to R wave) changes in FHR

■ The roughness (STV present) or smoothness (STV absent) of the FHR tracing

■ May be decreased/absent due to alterations in the CNS or inadequate fetal oxygenation

Long-Term Variability (LTV)

■ Describes the oscillatory changes that occur in 1 minute

■ Results in waviness of baseline

Decreases in BTBV

Beat-to-beat variability decreases with:

■ Fetal acidemia

■ Fetal asphyxia

■ Maternal acidemia

■ Drugs (narcotics, MgSO4, barbiturates, etc.) Increases in BTBV

Beat-to-beat variability increases with mild fetal hypoxemia.

Variable decelerations are abnormal.

They are classified as: Mild

Moderate

Severe

May signify fetal acidemia.

If an FHR of 160 bpm lasts for > 10 minutes, then tachycardia is present.

No BTBV (beat to beat variability) = fetal acidosis, and the fetus must be delivered immediately.

BTBV (beat to beat variability) can be reliably determined only with internal FHR monitoring (fetal scalp electrode).

Short-term variability is thought to be the most important predictor of fetal outcome.

Prolonged Decelerations

Isolated decelerations that last 2 to 10 minutes. Causes include:

■ Cervical examinations

■ Uterine hyperactivity

■ Maternal hypotension ^ transient fetal hypoxia

■ Umbilical cord compression

Management

■ Stop Pitocin/prostaglandins.

■ Change maternal position.

■ Administer IV fluids.

■ If mother is hypotensive, administer ephedrine/terbutaline.

■ Administer maternal O2.

■ Rule out cord prolapse.

ABNORMAL LABOR PATTERNS

Prolonged latent phase (see Table 6-3)

Active phase abnormalities—may be due to cephalopelvic disproportion (CPD), excessive sedation, conduction analgesia, and fetal malposition (i.e., persistent OP).

■ Protraction disorders—a slow rate of cervical dilation or descent

■ Arrest disorders—complete cessation of dilation or descent (see Table 6-3)

If a deceleration has occurred without recovery after 2 minutes, an emergency C-section is required.

INDUCTION OF LABOR

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