| Day 0 | Ovulation | Release of the oocyte from the dominant follicle; formation of the corpus luteum (CL). |
| Day 5-6 | Uterine Entry | The early blastocyst (conceptus) enters the uterine lumen from the oviduct. |
| Day 6-16 | Intrauterine Migration | The spherical conceptus (encased in a glycoprotein capsule) undergoes continuous mobility throughout both uterine horns and uterine body. This mobility is mediated by prostaglandin-induced myometrial contractions and is essential for maternal recognition of pregnancy (MRP) to prevent luteolysis. |
| Day 16-17 | Fixation | The conceptus becomes spatially fixed at the base of one uterine horn due to increasing diameter and reduced uterine tone. Fixation is not equivalent to implantation; the conceptus remains unattached at the cellular level. |
| Day 20-30 | Early Apposition | The trophoblast begins closer apposition to the endometrial epithelium; the glycoprotein capsule gradually thins. No true interdigitation yet occurs. |
| Day 35-40 | Initial Attachment (Implantation) | The trophoblast establishes stable microvillar interdigitation with the endometrial luminal epithelium. This marks the beginning of definitive chorioallantoic placentation. |
| Day 40 | Progressive Placentation | Development of a diffuse, epitheliochorial placenta with extensive microcotyledonary interdigitation across the endometrium. |