Objective: To assess the relationship between visualization of ectopic pregnancy (EP) on transvaginal ultrasound scan (TVS) and the gestation of EP.
Methods: Retrospective review of hospital notes of all women with histologically confirmed EP treated at Christchurch Women’s Hospital from January 2007 to July 2008. Data was collected for findings at initial TVS and gestation by estimated date of LMP.
Results: 143 cases of histologically confirmed EP were identified. 121 patients had gestation and TVS findings documented. The EP was identified on TVS in 111/140 (79%) cases. At gestations ≤27 days from LMP, 17/21 of EPs were visualized on TVS. At gestations 28 – 34 days from LMP 8/8 EPs were visualized; at gestations 35 – 41 days 16/19 of EPs were visualized; at gestations 42 – 48 days 23/29 of EPs were visualized; at gestations 49 – 55 days 21/28 of EPs were visualized; at gestations ≥ 56 days, 13/16 of EPs were visualized. The sensitivity of TVS for detecting EP was independent of reported gestation.
Conclusion: A single TVS is an effective test for detection of EP. This effectiveness appears unrelated to the reported gestation of pregnancy. This finding persists at gestations above five weeks which are more likely to be genuine. Documented LMP dates may be an unreliable estimation of duration of pregnancy given the number of women reporting pregnancies of less than 28 days gestation. The decision on whether to perform a TVS in cases of suspected EP should not be influenced by reported gestation.