Heterotopic pregnancy in a spontaneous conception presenting as a complex adnexal mass

Heterotopic pregnancy (HP), although common with assisted reproductive techniques, is very rare in spontaneous conceptions. We report the case of a HP in a 41-year-old lady who presented to us with a viable intrauterine pregnancy and an adnexal mass. The ectopic pregnancy was not suspected at her initial presentation. Although cases of HP presenting with ruptured ectopic pregnancy have been reported, HP presenting as pregnancy with a complex adnexal mass with no signs of acute abdomen (chronic ectopic) is rare and has not been reported in Brunei Darussalam. A high index of suspicion is needed to diagnose HP in a low risk woman conceiving spontaneously.