– in the medical literature of the last 50 years there are 57 cases of ectopic pregnancy after hysterectomy – 31 early, presumed to have occurred prior to the procedure, and 27 late, that occurred years after the hysterectomy. The presumed mechanism is the presence of a vaginal fistula or of fallopian tube prolapse.
– the incidence of heterotopic pregnancy (coexistence of intrauterine + ectopic pregnancy) is 1:6,000 – 1:8,000 – increasing, more likely to occur after fertility treatment.
– the sensitivity of urine qualitative bHCG is 95 – 99% – lower in early pregnancy and with dilute urine.
So, consider ectopic pregnancy in all women of fertile age even if they had a hysterectomy. And if your clinical suspicion is fairly high, use serum bHCG to rule it out, just a negative urine pregnancy test is not enough.