Fetal monkey surfactants after intra-amniotic or maternal administration of betamethasone and thyroid hormone

OBJECTIVE: To compare direct intra-amniotic injection of betamethasone and thyroxine (T4) with maternal treatment and controls for accelerating pulmonary surfactant production. METHODS: Twelve pregnant monkeys (Macaca mulatta) on gestational day 125 (term 165 +/- 10 days) had surfactant protein A and B concentrations measured in amniotic fluid. In four controls, normal saline was injected into the amniotic fluid; four others (intra-amniotic) received intraamniotic betamethasone (1 mg) and T4 (60 mug); and in four others (maternal), the dam was given betamethasone (12 mg) intramuscularly, repeated in 24 hours, plus = (400 mug) intravenously, repeated every 6 hours for 24 hours. Seventy-two hours after the initial amniocentesis, a hysterotomy was performed and fetal tissue and amniotic fluid harvested for determination of surfactant protein A and B concentrations and immunohistochemical staining for surfactant protein A. RESULTS: Amniotic fluid surfactant protein A was higher,with intra-amniotic injection than with maternal treatment (P < .04) or controls (P = .07). Amniotic fluid surfactant protein B was higher in the intra-amniotic group than in controls (P = .06). Immunohistochemical. staining for surfactant protein A in the lung tissue was increased in the intra-amniotic group compared with controls (0.145 +/- 0.01 versus 0.097 +/- 0.001, percent positive staining for surfactant protein A cells per lung tissue cells; P < .03). Birth weight was greater in the intra-amniotic group compared with the maternal group (P < .03) although not different from the controls. Finally, gut motility and the presence of formed meconium were increased in the intra-amniotic group compared with the other groups (P < .05). CONCLUSION: Intra-amniotic injection of betamethasone and T4 enhanced lung (and possibly intestinal) maturation of the preterm rhesus fetal monkey compared with maternal injections. (C) 2001 by the American College of Obstetricians and Gynecologists.