Transamniotic stem cell therapy (TRASCET) with donor mesenchymal stem cells (MSCs) has been shown experimentally to reverse central effects of intrauterine growth restriction (IUGR). We sought to compare amniotic-fluid and placenta-derived MSCs (afMSCs and pMSCs, respectively) as TRASCET donor cells in a murine IUGR model.Pregnant Sprague-Dawley dams (n=8) were exposed to alternating 12-hour hypoxia (10.5% O2) cycles, starting on gestational day 15 (E15; term=E21-22). On E17, fetuses (n=100) were divided into four groups. An untreated group had no further manipulations (n=24). Three groups received volume-matched intra-amniotic injections of either saline (sham; n=27), or suspensions of afMSCs (n=24), or pMSCs (n=25). Normal fetuses served as controls (n=21). All infused MSCs consisted of syngeneic Lewis rat cells phenotyped by flow cytometry and GFP-labeled. At term, fetal and placental morphometrics were calculated, and placental TNF-α levels were determined by ELISA. Statistical comparisons were by Fischer's T-test or Wilcoxon rank sum test (p≤0.05).Overall survival of the hypoxic groups was 83% (83/100). Compared to normal, maternal-adjusted fetal weights were significantly decreased in all hypoxia groups (pairwise p<0.001), however only the afMSC group showed higher adjusted-fetal weights than sham (p<0.001). Placental efficiency was decreased in untreated, sham, and pMSC groups (p<0.001-0.056) but normalized in the afMSC group (p=0.205). Maternal-adjusted placental weights were lower than normal in all hypoxia groups (p<0.001-0.045), except for the pMSC group (p=0.387).Amniotic fluid-derived mesenchymal stem cells are superior to their placenta-derived counterparts in transamniotic stem cell therapy for intrauterine growth restriction in a rat model.Basic/Translational science.