PRETERM BETAMETHASONE TREATMENT OF FETAL SHEEP - OUTCOME AFTER TERM DELIVERY

OBJECTIVES: Although antenatal corticosteroids improve outcomes for pr eterm newborns, negative effects could result if preterm delivery does not occur. We investigated whether betamethasone treatment of preterm fetal sheep would alter cardiovascular, renal, and lung function afte r delivery al term. METHODS: Preterm fetal lambs were randomized at 12 6-128 days' gestation to receive single doses of saline (n = 6) or 0.5 mg/kg betamethasone (n = 7) by ultrasound-guided fetal intramuscular injection. The lambs were delivered by cesarean at term, 20 clays afte r fetal treatment, then ventilated for 4 hours to evaluate lung, cardi ovascular, renal, and endocrine newborn adaptive responses, as well as responses lo mild hypoxia. RESULTS: Body and organ weights (brain, lu ng, heart, kidney, adrenal) were similar in the two groups. Values for blood gases and pH, mean arterial pressures, heart rates, glomerular filtration rates, renal osmolar clearance, and plasma cortisol, angiot ensin II, epinephrine, and norepinephrine levels were similar between groups for 3 hours after delivery and before hypoxia. A 20-minute peri od of mild hypoxia resulted in increases in catecholamines, arginine v asopressin, and atrial natruretic factor in both betamethasone-treated and control lambs. However, hypoxia did nor alter cardiovascular or l ung function in either group. After reversal of hypoxia, measured phys iologic parameters did riot differ between groups. Kidney Na, K-adenos ine triphosphatase activity was significantly higher for the betametha sone-treated lambs. CONCLUSION: Preterm fetal betamethasone administra tion does not alter neonatal pulmonary, cardiovascular, renal, or endo crine physiology after term delivery or in response to mild hypoxia.