late decelerations fetal heart rate

Everly

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18-03-2025

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Late decelerations in fetal heart rate (FHR) are a cause for concern during labor and delivery. They indicate a potential problem with how well the baby is tolerating the stress of contractions. This article will explore what causes late decelerations, how they're identified, and what management strategies are employed.

What are Late Decelerations?

Late decelerations are a type of periodic FHR change. They are defined as a decrease in the fetal heart rate that begins *after* the onset of a uterine contraction and returns to baseline *after* the contraction ends. Crucially, the nadir (lowest point) of the deceleration occurs *after* the peak of the contraction.

Unlike early decelerations, which are typically benign, late decelerations signal potential fetal distress. This is because they suggest uteroplacental insufficiency – a reduction in oxygen and nutrient transfer from the mother to the fetus through the placenta.

Causes of Late Decelerations

Several factors can contribute to late decelerations. The most common underlying cause is uteroplacental insufficiency. This can stem from various conditions, including:

• Placental Abruption: Premature separation of the placenta from the uterine wall.
• Placenta Previa: Placenta partially or completely covers the cervix.
• Maternal Hypertension: High blood pressure reduces placental blood flow.
• Uterine Hyperstimulation: Excessive or prolonged contractions reduce blood flow to the placenta.
• Postmaturity: Pregnancy extending beyond 42 weeks, potentially leading to placental aging.
• Diabetes Mellitus: Can affect placental function.
• Intrauterine Growth Restriction (IUGR): The fetus is smaller than expected for gestational age.

Identifying Late Decelerations

Late decelerations are identified using electronic fetal monitoring (EFM). This involves attaching sensors to the mother's abdomen to monitor both the fetal heart rate and uterine contractions. A trained healthcare professional analyzes the FHR tracing to identify the characteristic pattern of late decelerations.

The visual appearance on the tracing is key. The deceleration begins after the contraction starts, and the lowest point of the deceleration (nadir) lags behind the peak of the contraction. This timing is the crucial difference between late and early decelerations.

Management of Late Decelerations

The management of late decelerations depends on their severity and duration. It's essential to act quickly to improve fetal oxygenation. Interventions may include:

• Changing Maternal Position: Left lateral positioning can improve placental blood flow.
• Oxygen Administration: Providing supplemental oxygen to the mother increases oxygen levels in the fetal blood.
• Increasing IV Fluids: Expanding maternal blood volume can improve placental perfusion.
• Reducing Uterine Activity: Medications such as terbutaline may be used to decrease the frequency and intensity of contractions.
• Amnioinfusion: Infusing warmed saline into the amniotic sac can help cushion the umbilical cord and improve fetal blood flow.
• Immediate Delivery: If late decelerations are severe or unresponsive to other interventions, immediate delivery (either vaginal or cesarean) may be necessary to prevent fetal hypoxia (lack of oxygen).

What to Expect During Monitoring

If late decelerations are detected, your healthcare provider will closely monitor you and the baby. They will likely perform a thorough assessment, including checking your blood pressure, pulse, and uterine contractions. Frequent fetal heart rate monitoring will continue. The provider will explain the situation and the interventions being considered.

Conclusion

Late decelerations in fetal heart rate are a significant finding during labor. They signal potential fetal compromise due to uteroplacental insufficiency. Prompt recognition and appropriate management are critical to ensuring a safe outcome for both mother and baby. Understanding the causes, identification, and management strategies is vital for healthcare professionals and expectant parents.

Further Reading

For more detailed information on fetal heart rate monitoring and late decelerations, consult reputable resources such as the American College of Obstetricians and Gynecologists (ACOG) website.

(Remember: This information is for educational purposes only and should not be considered medical advice. Always consult with a healthcare professional for any concerns regarding your pregnancy or labor.)