What are the causes of ectopic pregnancy in IVF?

After successful embryo transfer into the uterine cavity during IVF procedures, embryos typically remain free-floating within the uterus for three to four days before finding an optimal implantation site. During this period, if the embryo fails to implant in the uterine cavity and instead migrates into the fallopian tube and implants there, it results in an ectopic pregnancy. The degree of patency of the fallopian tubes is directly related to the occurrence of ectopic pregnancy—tubal obstruction can lead not only to infertility but also to ectopic pregnancy. Ectopic pregnancies can occur even in women who conceive naturally, as well as in those undergoing IVF, and may result in miscarriage or preterm birth.