Fetal growth restriction during pregnancy has been shown to reduce fetal renal development and nephron allotment due to in utero nutrient restriction. Decreased fetal kidney weight is further associated with altered renal function after delivery (e.g. hyperfiltration) and may result in adult hypertension and/or chronic renal failure as described by the Barker Hypothesis. Herein, a novel model of uterine space restriction was developed that may facilitate understanding of renal development. Our purpose was to evaluate the effects of reduced uterine space on fetal growth and renal development in late ovine gestation. Multiparous ewes were studied: Control singletons, twins and triplets, and Unilateral singletons, twins and triplets. The Unilateral surgery consisted of a single uterine horn ligated and completely disconnected via removal of all intercorneal connections at least 2 months prior to pregnancy. These 6 groups were combined into 2 based on placental attachment sites per fetus. The non-uterine space restricted group (non-USR) consists of placentome #/fetus of ≥ 53.2±2.4 (Control singletons and twins, and unilateral singletons) while the uterine space restricted group (USR) consists of placentome #/fetus of ≤ 27.6±1.7 (Unilateral twins and triplets, and Control triplets). These treatments were decided based upon a clear demarcation in the number of placentomes/fetus in each group. For this study, fetuses were evaluated at either 120 or 130 days of gestation (term 147). Fetal weight (wt) and kidney wt were measured. Kidney tissues were fixed, stained for collagen by Gomori Trichrome, and examined microscopically for glomerular generation number (as measured by branching patterns). Fetal umbilical arterial blood was analyzed for plasma creatinine. In the USR group at 120 days gestation, fetal wts were not appreciably altered. At 130 days gestation, fetal wts were 18% lighter (P<0.03) in the USR group (3324±152g) compared to the non-USR group (4073±297). At 120 days gestation, kidney wts were 13% lighter (P<0.03) in the USR group (9.7 ± 0.5g) compared to the non-USR group (11.6±0.4g). At 130 days gestation, kidney wts were 24% lighter (P<0.01) in the USR group (9.7±0.2g) compared to the non-USR group (12.8±0.4). The USR kidneys had 12% fewer (P<0.01) glomerular generations (13.3±0.4) compared to the non-USR group (15.0±0.4) at 120 days and 14% fewer (P<0.01) glomerular generations (13.4±0.2) compared to non-USR (15.5±0.2) at 130 days. Fetal plasma creatinine levels were not altered at 120 days gestation, but at 130 days were 44% higher (P<0.01) in the USR group (2.2±0.2 mg/dl) compared to the non-USR group (1.5±0.1mg/dl). Space restriction did not alter calculated placental efficiency, defined by fetal weight/individual placental wt at either time point. In uterine restriction, IUGR became evident at 130 days gestation. The decreased kidney wt, glomerular generations, and increased plasma creatinine in the USR group support the concept that IUGR impairs renal development. The finding of higher creatinine levels in USR necessitates additional study because function of fetal kidney, as well as placenta, determine fetal plasma creatinine levels. This model is well suited to contrast the dynamic adaptations of the ovine placenta during rapid fetal growth and uterine restriction and further work is planned.(poster)