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 pulmon ary surfactant production. METHODS: Twelve pregnant monkeys (Macaca mulatta) on gestational day 125 (t erm 165 +/- 10 days) had surfactant protein A and B concentrations measured in amniotic fluid. In four controls, normal saline was injected into the a mniotic fluid; four others (intra-amniotic) received intraamniotic betameth asone (1 mg) and T4 (60 mug); and in four others (maternal), the dam was gi ven betamethasone (12 mg) intramuscularly, repeated in 24 hours, plus = (40 0 mug) intravenously, repeated every 6 hours for 24 hours. Seventy-two hour s after the initial amniocentesis, a hysterotomy was performed and fetal ti ssue and amniotic fluid harvested for determination of surfactant protein A and B concentrations and immunohistochemical staining for surfactant prote in A. RESULTS: Amniotic fluid surfactant protein A was higher,with intra-amniotic injection than with maternal treatment (P < .04) or controls (P = .07). Am niotic fluid surfactant protein B was higher in the intra-amniotic group th an in controls (P = .06). Immunohistochemical. staining for surfactant prot ein 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 sta ining 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 moti lity and the presence of formed meconium were increased in the intra-amniot ic 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 com pared with maternal injections. (C) 2001 by the American College of Obstetr icians and Gynecologists.