Objectives: To assess the relationship between visualization of ectopic pregnancy (EP) on transvaginal ultrasound scan (TVS) and serum quantitative HCG (HCG).
Methods: Retrospective review of women with histologically confirmed EP treated at Christchurch Women’s hospital in 2007. Data collected for findings at initial TVS and serum quantitative HCG levels at that time. Visualization of EP was classified according to recognized published criteria.
Results: 137 cases of histologically confirmed EP identified. Initial TVS and HCG data available for 128 cases. The EP visualized on TVS in 79% of cases. There was a slight tendency for TVS to become more sensitive with rising HCG. However for the 2 groups, EP visualized and EP not visualized, there was no statistically significant difference in HCG levels.
Findings: At a BhCG < 500, TVS showed 75% sensitivity in detecting EP, 74% at BhCG < 1000, 74% at BhCG < 3000 and 76% at < 5000. Overall sensitivity in picking up EP on initial TVS is 79%.
Conclusions: A single TVS is an effective test for the detection of ectopic pregnancy, and appears to bear little relationship to the serum quantitative HCG level. Even in the presence of low HCG levels, ectopic pregnancies can be reliably visualised at the initial TVS. Therefore TVS should be the standard first line investigation in cases of suspected ectopic pregnancy The decision whether or not to perform TVS in such cases should not be influenced by HCG level.