OBJECTIVE: Leptin, the obesity gene product, plays a key role in the regulation of energy metabolism and is correlated with fetal growth and development, but the mechanisms are not clearly understood. This study aimed to explore the relationship between soluble leptin receptor (sOB-R) in cord blood and fetal growth and development. METHODS: According to the birth weight, 67 full-term newborns were divided into two groups; the small for gestational age group (SGA group, n = 23) and the appropriate for gestational age group (AGA group, n = 44). The levels of leptin and sOR-R were assayed by ELISA and the nutrional state of the newborns was evaluated with body fat content measured by the Weststrate formula. RESULTS: The sOB-R level in cord blood was negatively related to leptin in cord blood, birth weight and body fat content ( r = -0.405, -0.366, -0.356 respectively; all P <0.05) and it was not related to maternal leptin level and sOB-R. The sOB-R level in cord blood in the SGA group was significantly higher than that in the AGA group [(18.24±6.02) ng/ml vs (13.8014.37) ng/ml; P <0.01], whereas the leptin level in the SGA group was much lower than that in the AGA group [(6.79±4.59) ng/ml vs (16.30±11.62) ng/ml; P<0.01]. The sOB-R level in cord blood in male infants was higher than that in female ones [(16.8914.37) ng/ml vs (13.9515.29) ng/ml; P <0.05], but the leptin level in the former was lower than that in the latter [(10.2818.28) ng/ml vs (15.70 ±12.11) ng/ml; P <0.05]. CONCLUSIONS: sOB-R in cord blood may have effects on fetal growth and development by regulating the serum level of free leptin. Quantification of both circulating leptin and sOB-R levels may be more valuable for understanding the mechanism of leptin.