Fetal cardiorespiratory and neurobehavioral response to zidovudine (AZT) in the baboon

OBJECTIVE: To evaluate the effects of intravenous of zidovudine (AZT) at a dose and duration of infusion comparable to that used clinically on parameters reflective of fetal well-being. METHODS: Thirteen chronically instrumented noninfected baboons were monitored during intravenous infusions of AZT. Fetal cardiorespiratory activity and neurobehavioral function were assessed with 4-48-hour infusion of AZT to ten mothers (0. 5-2.1 mg/kg per hour) and three fetuses (2-6 mg/h), which resulted in fetal plasma concentrations of AZT of 194-3100 ng/ml. RESULTS: No significant differences were found in the mean values in control periods, before and after infusion with values during infusion for parameters of fetal heart rate and rate variability (n = 7), breathing activity (n = 8), electroencephalographic activity (n = 8), and behavioral state (n = 7). No correlations were found with drug level. CONCLUSIONS: The absence of associations between exposure of the fetal baboon to AZT and changes in parameters reflective of fetal condition suggests that comparable exposure of the human fetus during intravenous infusion of drug would not confound clinical monitoring used to assess fetal well-being. These findings supplement conclusions from clinical research in support of U.S. Public Health Service recommendations that intrapartum fetal monitoring be performed as clinically indicated, not specifically because pregnant patients are treated with intravenous AZT.