Maternal effects influence the inheritance pattern of nuclear genes in which the genotype of the mother directly determines the phenotype of the offspring.As a subterranean rodent,mandarin voles (Lasiopodomys mandarinus) adapt to their hypoxic environment and so they are an excellent model for studying maternal effects in mammals.In the laboratory,4 groups (n= 8 animals per group) of voles were subject to chronic intermittent hypoxia during pregnancy or lactation or used as controls.The subjects were exposed 10%PO2 4hrs per day daily for 35 days.At the 90 days old,the offspring mortality,sex ratio,organ weight and hemogram were recorded.The results were as follows: chronic intermittent hypoxia during pregnancy (27.3%) and lactation (30.8%) resulted in greater 90-day mortality of offspring compared to the controls (12.5%) ,and sex ratio favoured females (0.29 male/female) in the pregnancy group or males (0.60) in the lactation group compared to the controls (0.40) .Adrenal gland mass was lower in the pregnancy group (2.68 ± 0.48 mg) than that of the control group (5.64 ± 0.99 mg) (P=0.023) .The hemogram did not differ significantly among the four groups.In conclusion,Mandarin vole offspring are better adapted to hypoxic conditions if exposed to hypoxia during their gestation than if exposed to hypoxia during suckling.