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

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.

Choice A rationale

Deep tendon reflexes of +1 are hypoactive reflexes, indicating decreased neurological excitability. In preeclampsia, central nervous system irritability is a key feature, often leading to hyperreflexia, which would be documented as +2, +3, or +4. Therefore, +1 reflexes are inconsistent with preeclampsia.

Choice B rationale

3+ protein in the urine indicates significant proteinuria, which is a hallmark sign of preeclampsia. The kidneys are affected in preeclampsia, leading to increased excretion of protein in the urine.

Choice C rationale

A blood pressure of 148/98 mm Hg is elevated and falls within the diagnostic criteria for preeclampsia, which is hypertension (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg) that develops after 20 weeks of gestation along with proteinuria or other signs of end-organ damage.

Choice D rationale

Pitting sacral edema, or swelling in the sacral area that leaves a pit when pressed, is a common finding in preeclampsia due to fluid retention and increased capillary permeability.