A 29 year old woman presents to the early pregnancy unit with lower abdominal pain and vaginal spotting at 7 weeks gestation by dates. She has had one previous miscarriage. Her blood pressure is 100 over 62 mmHg, pulse 96 beats per minute and she has mild suprapubic tenderness. Transvaginal ultrasound shows an empty uterus and a 2.5 cm adnexal mass with a yolk sac in the right fallopian tube. What is the most appropriate management?