Sympathetic nervous system (SNS) mediated peripheral vasoconstriction plays a key role in initial maintenance of blood pressure during rapid onset asphyxia in the mammalian fetus, but is attenuated after the first few minutes. It is unclear whether the SNS response is sustained during the brief but frequently repeated episodes of asphyxia characteristic of labor. In the present study, 14 fetal sheep at 0.85 of gestation received either chemical sympathectomy with 6-hydroxydopamine (6-OHDA, n = 7) or sham injection (control, n = 7), followed 4-5 days later by repeated 2-minute episodes of complete umbilical cord occlusion every 5 minutes for up to 4 hours or until mean arterial blood pressure (MAP) fell to < 20 mmHg for 2 successive occlusions. In controls, umbilical cord occlusions were associated with a rapid initial fall in fetal heart rate (FHR) and femoral blood flow (FBF), with initial hypertension, followed by progressive development of hypotension during ongoing occlusions. Sympathectomy was associated with attenuation of the initial rise in MAP during umbilical cord occlusion, and after the onset of hypotension, markedly more rapid fall of MAP to the nadir, with a correspondingly slower fall in FBF (P < 0.05). In contrast, MAP and FHR between successive occlusions were higher after sympathectomy (P < 0.05), and there was no significant difference in the number of occlusions before terminal hypotension (16.1 ± 2.2 vs. control; 18.7 ± 2.3). These data show that SNS activity provides ongoing support for fetal MAP during prolonged exposure to brief repeated asphyxia.