Which fetal heart rate pattern is most concerning during labor?

• A. Early decelerations
• B. Variable decelerations
• C. Late decelerations
• D. Sinusoidal pattern

Answer: (C)

Fetal heart rate patterns during labor are clues about how well the fetus is being oxygenated. When a deceleration occurs, the timing relative to contractions helps distinguish the cause and the level of concern. Late decelerations start after the peak of a contraction and indicate that placental blood flow is not adequate during labor—uteroplacental insufficiency. This means the fetus may be experiencing hypoxemia, and repeated or persistent late decelerations signal a real risk to fetal well-being, requiring prompt assessment and intervention to restore placental perfusion and oxygen delivery. Typical responses include repositioning the mother to a left lateral stance to improve uteroplacental flow, stopping or slowing oxytocin to reduce contraction intensity, giving supplemental oxygen, ensuring adequate IV fluids, and escalating care if the pattern continues or worsens (often involving the obstetric team and consideration of delivery if needed).

Early decelerations, caused by fetal head compression, are generally reassuring and mirror contractions without indicating hypoxia. Variable decelerations result from cord compression and can vary in shape and timing; they require evaluation but aren’t as consistently tied to placental insufficiency as late decelerations. A sinusoidal pattern is far more ominous, often signaling severe fetal anemia or profound hypoxia and demanding immediate, aggressive intervention. Within the patterns listed, late decelerations reflect a real concern for placental perfusion during labor and typically drive urgent assessment and response.