Abstract: Objective To explore the related factors of premature delivery of pregnant ewes after intrauterine fetal cardiac intervention. Methods Eight bigeminal pregnant ewes (between 101 to 127 d of the gestation) were undergone intrauterine fetal cardiac intervention. The heart rate, blood pressure，blood gas value and glucose levels of the ewes were monitored during the procedure. The levels of estradiol, progesterone, catecholamine and interleukins of the ewes were compared before surgery, right after surgery and 48 hours post-surgery. Results There were no significant changes on the heart rate,blood pressure and blood gas value during and afler surgery, the blood glucose levels slightly increased.The level of estradiol, progesterone and catecholamine demonstrated with significantly increasing after surgery(P<0.05). Fourty-eight hours aftersurgery, the values of Estradiol, Estradiol/progesterone recovered to the same level as that before surgery in mature delivery group，while in premature delivery group，Estradiol value remained in a high level. Interleukin-6 level significantly increased just afler surgeiy (P<0.05). 48 hours after surgery，Interleukin-6 level decreased significantly in mature delivery group (P<0.05)while it maintained in a high level in premature delivery group. Conclusion The changes of estradiol, progesterone, catecholamine and interleukin-6 could be the related factors that affect the premature delivery of pregnant ewes after intrauterine fetal cardiac intervention.

Key words: Premature delivery, Pregnant ewes, Fetal lamb, Intrauterine cardiac intervention