[Interstitial pregnancy: a rare type of ectopic pregnancy]

Three women, aged 21, 28 and 37 years, respectively, were diagnosed with interstitial pregnancies. The first patient presented with lateral abdominal pain, the second patient was asymptomatic and consulted the physician for a routine first trimester scan and the third patient had painless vaginal bleeding in the first trimester. Each was treated with systemic methotrexate in a multiple dose regimen, which was successful in the latter two patients. The first patient was discharged in good condition after her last methotrexate injection, but developed severe abdominal pain and collapsed at home after the interstitial pregnancy had ruptured. She underwent surgery and recovered. Today, the incidence of ectopic pregnancy in the Netherlands is around 8 per 1000 live births. Interstitial pregnancies, which nidate in the portion of the fallopian tube embedded in the uterine wall, account for 2-3% of all ectopic pregnancies. A urinary pregnancy test should be performed for any fertile woman with abdominal pain or abnormal vaginal bleeding. If the result is positive, the patient should be referred to a gynaecologist for transvaginal ultrasound to exclude ectopic pregnancy. In case of a pregnancy of unknown location, one should search for specific ultrasound markers of non-tubal ectopic pregnancy and assess serum human chorionic gonadotropin (HCG). Interstitial ectopic pregnancy should be considered if the serum HCG level is above 2000 U/l.