A 37-year-old woman, gravida 2 para 1, arrived in our emergency clinic at 16 2/7 weeks of a spontaneously conceived pregnancy for abdominal pain. She was on oral antibiotics for 2 days to treat a suspected urinary tract infection with no improvement. Blood tests, abdominal ultrasound and intrauterine fetus were all normal. She left our emergency unit with laxatives. Four days later, she returned to our clinic with severe abdominal pain. We repeated abdominal and foetal ultrasonography and identified a left para-uterine 7×5 cm mass. As adnexal torsion was suspected, we performed an emergency laparoscopy. At laparoscopy, we found a left haematosalpinx and realised a left salpingectomy. Histology confirmed the presence of a heterotopic pregnancy (HP). This case illustrates the importance of exploring the adnexa in a gravid woman presenting with abdominal pain in the first and early second trimesters. Although rare, excluding a HP may prevent a life-threatening haemorrhage.