Our aim was to investigate the hypoglycaemic and antioxidant effects of the Helichrysum plicatum ssp. plicatum (HPsP) plant extract in the streptozotocin-induced type 1 diabetes rat model during pregnancy. Five groups (n = 8, each) were formed: (1) diabetic non-mated control, (2) non-diabetic mated control, (3) diabetic mated control, (4) diabetic non-mated treatment and (5) diabetic mated treatment. The HPsP extract was administered orally for 15 days (250 mg/kg body weight), beginning 3 days before mating. The extract led to decreased blood glucose, increased serum insulin, and decreased serum triglycerides in pregnant and non-pregnant diabetic animals. Liver thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) measurements in extract-treated diabetics were similar to non-diabetic pregnant controls, indicating probable reversal of increased lipid peroxidation in the liver. The mean pup number tended to increase (p = 0.06) with extract administration. In conclusion, the beneficial effects we encountered with the periconception use of the studied herbal extract warrant further investigation.