Assisted Reproduction and the Multiple Pregnancy:

Heterotopic pregnancy is defined as an intrauterine pregnancy that coexists with an ectopic pregnancy. Many predisposing factors contribute to this condition and include pelvic inflammatory disease, endometriosis, and ovulation induction. In vitro implantation with multiple embryos has caused an increased rate of heterotopic pregnancies. The demonstration of an intrauterine pregnancy is no longer a reliable indicator for excluding an ectopic pregnancy.