Temporary ischaemia of one uterine horn of anaesthetized, 9-day pregnant rats was induced by occluding the uterine blood vessels with forceps. The effects on the embryo of 30, 60 or 120 min of ischaemia was examined with the maternal abdominal temperature maintained at 32, 35 or 37\s=deg\C. Ischaemia caused a reduction in fetal survival at all treatment levels. Higher abdominal temperatures caused a greater reduction in fetal survival, as did longer periods of ischaemia. The incidence of fetal

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... alformation was greater in ischaemic than in control horns although specific treatment effects were not apparent. Fetal weights were reduced in the ischaemic horns, especially at the higher abdominal temperatures. These findings show that abdominal temperature can influence the effects of ischaemia and suggest that the embryo is less resistant to uterine ischaemia than was previously thought.