BACKGROUND: The creatine-creatine kinase-phosphocreatine (Cr-CK-PCr) system maintains intracellular ratios of ATP/ADP for support of cellular functions and has been characterized at the placental-uterine interface of rodents, primates, swine and sheep, and thus may support fetal development. This study determined effects of dietary supplementation of creatine (Cr) to gestating gilts on fetal development, the number and ratio of primary and secondary muscle fibers, and on protein expression in endometrium and fetal biceps-femoris muscle, respectively in fetal pigs on d 60 and d 90 of gestation. METHODS: Reproductively mature gilts were synchronized to estrus using Matrix, observed for estrus (d 0), and artificially inseminated 12 h and 36 h later. Gilts were individually housed and fed 0.86 kg of 14% crude protein diet twice daily that meets nutritional requirements for pregnant gilts. Gilts were assigned to either basal diet control (CON) group, or Cr supplemented group (provided 30 g Cr monohydrate daily) from d 10 to either d 60 or d 90 of gestation. Gilts were euthanized and hysterectomized on either d 60 or d 90 of gestation. These protocols were completed in two replicates, as gilts were bred in spring and euthanized in summer or bred in fall and euthanized in winter (n = 20 gilts/replicate). Litter size, crown-rump length, sex, and fetal weight was recorded. Three female and male fetuses closest to mean litter weight were selected to assess effects of treatment on weight of fetal brain, kidney, liver, spleen, and biceps-femoris muscle. Data were analyzed to determine effects of treatment, days of gestation, replicate, and sex on litter size, fetal measurements, and incidence of intrauterine growth restriction. RESULTS: Dietary Cr supplementation increased fetal brain weight to body weight ratios on d 90 of gestation (P < 0.05) and fetal kidney weight to body weight ratios on d 60 of gestation (P < 0.01), while days of gestation had significant effect on expression of mitochondrial CK isoform in gilt endometria (P < 0.05). CONCLUSIONS: Results suggest that dietary supplementation of Cr in gestating gilts enhanced development of select fetal organs and contribute to understanding roles of the Cr-CK-PCr system in pregnancy.