Aim To study the effects of chronic intrauterine hypoxic on myocardial inducible nitric oxide synthase(iNOS) and plasma endothelin-1(ET-1). Methods Chronic intrauterine hypoxic rats were divided into three groups:hypoxic group,air mimic control group and blank control group.Each group included 10 offspring rats.We monitored the weight of organs and birth weight of offspring,immunohistochemistry was used to examine the expression of myocardial iNOS,enzyme linked immunosorbent assay(ELISA) was used to measure serum ET-1 expression of offspring at 1 day and 6 month old. Results Organ/body weight percentage showed chronic intrauterine hypoxia could cause a disproportionate growth of offspring organs.The expression of myocardial iNOS of the hypoxic group significantly increased compared with that of the air mimic control group and that of the blank control group(P<0.05),but the air mimic control group was not significantly different from that of the blank control group(P>0.05).There was no significant difference of the expression of the serum ET-1 of all groups of offspring at 1 day old(P>0.05).But there was significant difference of the expression of the serum ET-1 of the hypoxic group compared with that of the air mimic control group and that of the blank control group of offspring at 6 month old(P<0.05),while and the air mimic control group was not significantly different from that of the blank control group(P>0.05). Conclusions Intrauterine chromic hypoxia may be a stress factor for development of the cardiovascular system,and it can induce low birth weight and high expression of myocardial iNOS and serum ET-1,which lead to increase the risk of cardiovascular disease.