Heterotopic interstitial pregnancy in natural conception is very rare. Definitive diagnosis is
made by systematic pelvic ultrasound. Simultaneous viable conception observed in both intraand extra-uterine is pathognomonic of heterotopic interstitial pregnancy. We report a 34-yearold woman primigravida at 10 weeks’ amenorrhoea who underwent evacuation of retained
product of conception for missed miscarriage. Intraoperatively, minimal product of conception
was retrieved. Bedside pelvic ultrasound showed cystic mass at right superolateral part of
uterine fundus suspicious of interstitial pregnancy. Cornual resection was performed via
laparotomy. Histopathological examination showed presence of product of conception and
interstitial pregnancy. Serum β-human chorionic gonadotropin dropped from 10,027 IU/l on day
one post-ERPC to 210 IU/l at day three post-cornual resection. This case report highlighted
the challenge in diagnosing heterotopic interstitial pregnancy conceived naturally. Timely
diagnosis may avert dire consequences of massive haemorrhage from ruptured uterine cornua