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What is the most likely cause for variable fetal heart rate (FHR) decelerations?

A.

Fetal hypoxemia.

B.

Altered fetal cerebral blood flow.

C.

Uteroplacental insufficiency.

D.

Umbilical cord compression.

Answer and Explanation

The Correct Answer is D

Choice A rationale

Fetal hypoxemia, a deficiency in oxygen reaching the fetal tissues, typically manifests as late decelerations in the fetal heart rate tracing, which reflect uteroplacental insufficiency. While severe hypoxemia can lead to various FHR patterns, variable decelerations are more directly associated with mechanical factors affecting the umbilical cord.

Choice B rationale

Altered fetal cerebral blood flow can be a consequence of various factors, including hypoxemia and cord compression, and can influence the fetal heart rate. However, variable decelerations are specifically caused by events that directly impede blood flow through the umbilical vessels rather than a generalized alteration in cerebral circulation.

Choice C rationale

Uteroplacental insufficiency, a condition where the placenta is unable to deliver an adequate supply of oxygen and nutrients to the fetus, typically results in late decelerations, indicating fetal distress due to chronic hypoxia. Variable decelerations, in contrast, have a more abrupt onset and recovery, reflecting acute changes in umbilical cord blood flow.

Choice D rationale

Umbilical cord compression occurs when the umbilical cord, which carries oxygen and nutrients to the fetus, is squeezed or constricted. This compression leads to a transient decrease in fetal blood flow and oxygenation, resulting in a rapid drop and subsequent return of the fetal heart rate, which is characteristic of variable decelerations. The shape, timing, and abrupt nature of variable decelerations directly correlate with the intermittent pressure on the umbilical cord.


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Related Questions

Correct Answer is B

Explanation

Choice A rationale

Wrapping the baby in warmed blankets addresses heat loss through conduction (direct contact with a cooler surface) and radiation (heat transfer to cooler surroundings). While helpful for maintaining warmth, it does not directly prevent heat loss from convection.

Choice B rationale

Convection is the loss of heat to cooler air currents moving across the skin surface. A blowing fan increases the rate of convective heat loss by continuously moving cooler air over the newborn. Moving the infant away from a blowing fan minimizes this heat transfer mechanism, thus preventing heat loss from convection.

Choice C rationale

Drying the baby after a bath primarily prevents heat loss through evaporation, as the evaporation of water from the skin surface cools the body. While important for thermoregulation, it does not directly address convective heat loss.

Choice D rationale

Placing the baby in a warmer, such as a radiant warmer, primarily prevents heat loss through radiation by providing a warm surface that emits infrared heat towards the infant. It also helps maintain the ambient air temperature, indirectly reducing convective heat loss, but moving away from a direct air current is the most direct way to prevent convection.

Correct Answer is {"A":{"answers":"B"},"B":{"answers":"A,B"},"C":{"answers":"B"},"D":{"answers":"B"}}

Explanation

Rationales for Each Condition

Neonatal Abstinence Syndrome (NAS)

  1. Temperature: Infants experiencing NAS often have difficulty regulating body temperature due to autonomic instability. While the newborn's temperature of 36.6°C (97.9°F) is within normal range, the use of a radiant warmer suggests challenges in maintaining thermoregulation, which is characteristic of NAS.
  2. Jitteriness: Jitteriness is observed in both hypoglycemia and NAS. In NAS, it is caused by neurological excitability due to opioid withdrawal, leading to tremors and hypertonia, which improve with soothing measures such as swaddling.
  3. Skin Color: Mottling is a frequent sign in neonates experiencing opioid withdrawal due to autonomic dysregulation. The absence of cyanosis or jaundice indicates that the mottling is due to withdrawal rather than an underlying pathology.
  4. GI Assessment: Loose stools and hyperactive bowel sounds are typical signs of NAS, caused by increased gastrointestinal motility due to withdrawal from opioids.

Hypoglycemia

  1. Jitteriness: Hypoglycemia is characterized by neuromuscular instability, leading to jitteriness. However, in this case, the newborn’s blood glucose level of 45 mg/dL is within acceptable neonatal range, making NAS a more likely explanation.
  2. Temperature, Skin Color, and GI Assessment: Hypoglycemia does not typically cause mottled skin or loose stools, making these findings more consistent with NAS.

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