Pharmacokinetic and Pharmacodynamic Investigations of Fetal Anesthesia During Maternal Fetal Surgery

This study examines how three medications commonly used during fetal surgery, fentanyl, rocuronium, and atropine, behave in the fetus. The primary goal is to understand their pharmacokinetics (how the drugs are absorbed, distributed, and cleared), pharmacodynamics (how they affect fetal physiology), and how they transfer between mother and fetus through the placenta. The secondary goal is to measure drug levels in discarded fetal blood samples collected during clinically indicated procedures and relate those levels to fetal heart rate, heart rate variability, movement, gestational age, and fetal size. An optional maternal blood draw component will allow comparison of maternal and fetal drug concentrations to better understand placental transfer. The study does not change clinical care or require extra fetal procedures, and findings may help create safer, evidence-based fetal anesthesia dosing strategies tailored to gestational age.