A laboring woman has received butorphanol intravenously (IV), 90 minutes before giving birth. Which medication should be available to reduce the postnatal effects of butorphanol on the neonate?

A. Doppler studies of the umbilical artery and other fetal vessels assess placental blood flow and fetal perfusion, which is particularly useful in cases of suspected IUGR. Abnormal Doppler readings, such as absent or reversed end-diastolic flow, indicate compromised placental function and increased fetal risk, guiding management decisions regarding timing of delivery and close surveillance.

B. While NSTs monitor fetal heart rate reactivity and overall fetal well-being, they do not directly assess placental blood flow or fetal growth restriction. NSTs are useful for ongoing fetal surveillance but are secondary in evaluating the etiology of IUGR.

C. These are important for monitoring fetal well-being, especially in high-risk pregnancies, but they cannot quantify growth or assess placental insufficiency. Movement counts are more of a screening tool rather than a diagnostic method for IUGR.

D. This procedure is typically used for genetic testing, fetal lung maturity, or assessment of certain infections, but it does not provide information about fetal size or placental blood flow. It is not a primary tool for evaluating IUGR.

A. Acute fetal distress is a contraindication because magnesium sulfate acts as a tocolytic, relaxing the uterus to suppress contractions. If the fetus is already in distress, inhibiting labor can delay delivery, prolong hypoxia, and worsen outcomes. In such cases, immediate delivery is prioritized, and magnesium sulfate should be withheld.

B. Gestational Diabetes Mellitus is not a contraindication. Clients with GDM may safely receive magnesium sulfate for seizure prophylaxis in preeclampsia or for preterm labor, though blood glucose should be closely monitored, as magnesium can occasionally affect insulin sensitivity.

C. Active labor at term is a contraindication because tocolysis is unnecessary and potentially harmful once the pregnancy has reached term. Suppressing contractions at this stage can increase maternal and fetal risks, such as prolonged labor, infection, and fetal compromise, and is therefore avoided.

D. Severe preeclampsia is an indication, not a contraindication. Magnesium sulfate is the drug of choice for preventing eclampsia by reducing the risk of maternal seizures. It is administered carefully with close monitoring of reflexes, respiratory status, and urine output to prevent toxicity.

E. Vaginal bleeding is a contraindication because it may indicate placental abruption, placenta previa, or other obstetric emergencies where immediate delivery is necessary. Administering magnesium sulfate in these situations could mask uterine tone, delay delivery, and worsen maternal-fetal outcomes, making it unsafe.