Implantation Bleeding: This is a common cause of spotting after embryo transfer, occurring when the embryo implants into the uterine lining, leading to light bleeding or spotting. It's a normal and expected part of the early pregnancy process for many women.

Hormonal Fluctuations: Changes in hormone levels, particularly estrogen and progesterone, which are crucial for maintaining the early pregnancy, can lead to spotting. These fluctuations can be due to the embryo transfer process itself or the hormonal support given during the IVF cycle.
Cervical or Uterine Irritation: The embryo transfer procedure can sometimes cause minor irritation to the cervix or uterus, leading to spotting. This is usually transient and resolves on its own.
Early Pregnancy Loss: Unfortunately, spotting can also be a sign of an impending miscarriage or early pregnancy loss. This is a significant concern after embryo transfer and requires close monitoring.

Ectopic Pregnancy: Although less common, ectopic pregnancy is a life-threatening condition where the embryo implants outside the uterus. Spotting, along with other symptoms like abdominal pain, can be indicative of an ectopic pregnancy, which requires immediate medical attention.
Ovarian Hyperstimulation Syndrome (OHSS): This is a potentially life-threatening complication of fertility treatment, characterized by enlarged ovaries and fluid accumulation in the body. Spotting can be one of the many symptoms, including abdominal pain, nausea, and vomiting.

Molar Pregnancy: A rare condition where abnormal tissue grows in the uterus instead of a fetus. Spotting can be one of the early signs, along with other symptoms like severe nausea and rapid uterine enlargement.
Uterine Rupture: An extremely rare but serious condition, especially in women with a previous uterine scar (from a cesarean section, for example). Spotting, along with severe abdominal pain and potentially life-threatening bleeding, can occur.