Table 2.

Comparison of commonly used animal models used to study human placentation.

Animal	Similarities	Differences	References
Mice	Chorioallantoic placenta Discoid, hemochorial placenta	Gross morphology and specific trophoblast cell types Yolk sac as major player in maternal–fetal exchange Placental labyrinth Trophoblast invasion limited to decidua Maternal and fetal blood separated by three trophoblast layers	[100,101,102]
Guinea pigs	Trophoblast invasion Hemochorial interface Pattern of placental development, especially the distribution pattern of trophoblast cell proliferation	Lobulated placenta with lobes as circulatory units Labyrinthine placentation	[103,104,105]
Horses	Trophoblast population has human counterparts with conserved essential properties Conserved transcription factors for trophoblast differentiation Extended length of gestation	Diffuse placenta with maternal–fetal exchange occurring across all available surfaces Temporal and spatial MHC expression regulation Endometrial epithelium, connective tissue, and uterine endothelium present	[86,106,107,108]
Non-human primates	Long gestational period Discoid, hemochorial placenta	Rapid but shallow trophoblast invasion	[109,110,111]