Which medication can transiently decrease FHR variability?

Which medication can transiently decrease FHR variability?

• A. Betamethasone
• B. Oxytocin
• C. Butorphanol
• D. Magnesium sulfate

Answer: (A)

Fetal heart rate variability reflects how the fetus’ autonomic nervous system responds to the intrauterine environment, and it can be temporarily altered by medications given to the mother that cross the placenta. An opioid analgesic used for labor analgesia can transiently depress the fetal central nervous system, leading to a short-lived decrease in beat‑to‑beat variability. This effect tends to resolve as the drug is cleared from fetal circulation, so the variability returns to baseline if there’s no ongoing hypoxia or other issue. Among common options, this class of drug fits the pattern of a temporary suppression of variability. Betamethasone is given to enhance fetal lung maturity and is not known for causing a meaningful, short-term drop in variability. Oxytocin can affect tracing if it causes tachysystole and resulting hypoxia, but it’s not a direct, predictable cause of transient variability reduction. Magnesium sulfate can depress fetal CNS and may reduce variability at higher levels, but the classic, most direct example of transiently decreased variability is an opioid analgesic given for labor pain.

Fetal heart rate variability reflects how the fetus’ autonomic nervous system responds to the intrauterine environment, and it can be temporarily altered by medications given to the mother that cross the placenta. An opioid analgesic used for labor analgesia can transiently depress the fetal central nervous system, leading to a short-lived decrease in beat‑to‑beat variability. This effect tends to resolve as the drug is cleared from fetal circulation, so the variability returns to baseline if there’s no ongoing hypoxia or other issue. Among common options, this class of drug fits the pattern of a temporary suppression of variability.

Betamethasone is given to enhance fetal lung maturity and is not known for causing a meaningful, short-term drop in variability. Oxytocin can affect tracing if it causes tachysystole and resulting hypoxia, but it’s not a direct, predictable cause of transient variability reduction. Magnesium sulfate can depress fetal CNS and may reduce variability at higher levels, but the classic, most direct example of transiently decreased variability is an opioid analgesic given for labor pain.