Negative histology with surgically treated tubal ectopic pregnancies - A retrospective cohort study

To determine the outcome of histological examinations of surgical specimens obtained from treatment of tubal ectopic pregnancy and to correlate with clinical findings, pre-operative ultrasound scans and the type of surgery.

A retrospective cohort study of 941 women diagnosed with a tubal ectopic pregnancy in the Early Pregnancy Unit and having surgical treatment at King's College Hospital, London. Clinical and ultrasound data had been entered contemporaneously on our electronic early pregnancy database and hospital clinical records over an 11year period from 2004 to 2014. Demographic data, clinical history, ultrasound scan parameters, type of surgical management and histological diagnosis were recorded. The primary outcome measure was the presence or absence of chorionic villi in the surgical specimen. Data were analysed using Mann Whitney U test for non-parametric data, relative risk for categorical data and binomial logistic regression.

A surgical specimen was obtained in 925 cases. Of these, 881/925 (95.2%) were positive for the presence of chorionic villi on histological examination. Patients with negative histology had a lower median gestational age, smaller ectopic pregnancies and lower serum human chorionic gonadotrophin levels. The relative risk of negative histology was significantly higher with a solid ectopic pregnancy on ultrasound (RR1.91, 95% CI 1.07-3.4) and with conservative surgery (RR 3.68, 95% CI 1.25-10.77). The relative risk was significantly lower with the presence of embryonic cardiac activity (RR 0.12, 95% CI 0.02-0.85). Only the serum hCG level was a significant predictor of negative histology on logistic regression analysis (p=0.048). In 39/44 women with negative histology, the human chorionic gonadotrophin level declined after surgery with no further intervention. Five of the 44 required a second surgical procedure as the ectopic pregnancy had been missed at the initial surgery and did not resolve.

There is lack of histological confirmation of sonographically diagnosed and surgically confirmed ectopic pregnancies in approximately 5% of cases, making this a relatively common finding following surgical treatment of tubal ectopic pregnancy. Clinicians should be aware of this when counselling women with tubal ectopic pregnancies about to undergo surgery, include this risk in the consent process and plan post-surgical follow up with this in mind.