Dear Editor,

We read with interest the manuscript “One size does not fit all: a nuanced approach to surgical management of interstitial ectopic pregnancy”1. While the paper provides an informative review on the subject of surgical options to treat interstitial ectopic pregnancy, we feel that the message regarding the criteria to diagnose this relatively rare form of ectopic pregnancy is confusing and potentially harmful. An interstitial pregnancy is classified as an ectopic pregnancy due to its location outside the uterine cavity. The key diagnostic criterion is the visualisation of the proximal segment of the interstitial tube adjoining the medial aspect of the gestational sac and the upper lateral aspect of the uterine cavity. This sign has been described by Ackerman et al2 in 1993, and has been adopted in the guideline on the diagnosis of ectopic pregnancy by the Royal College of Obstetricians and Gynaecologists3 and in the recommendations for good practice recently published by the European Society for Human Reproduction and Embryology4. The case shown in Figure 2 does not satisfy these criteria, and in our opinion, shows an early pregnancy which is implanted in the lateral aspect of the uterine cavity. As these laterally implanted pregnancies do not have significantly worse outcomes compared to other correctly sited pregnancies, we believe that this patient’s pregnancy was terminated unnecessarily. We are particularly concerned by the authors’ reference to their own paper5 showing a 50% false positive rate of interstitial pregnancies in their department resulting in the termination of 10 eccentrically implanted normal intrauterine pregnancies. The termination of a wanted normal intrauterine pregnancy should be considered a ‘never event’ and this view has been supported in the consensus published by the Society of Radiologists in Ultrasound Multispecialty Panel on Early First Trimester Diagnosis of Miscarriage6 which emphasised the need for adopting stringent criteria for non-viability to reduce the risk of inadvertent harm to a potentially normal pregnancy. This practice-changing consensus statement was the result of a joint effort by North American and European early pregnancy experts and professional societies. Perhaps the time has come to try to harmonise the criteria for the diagnosis of ectopic pregnancy as well to further improve the quality and safety of early pregnancy care worldwide.

Yours Sincerely

Dr Joel Naftalin, MD MRCOG, Dr Naaila Aslam MD FRCOG, Dr Cecilia Bottomley MD MRCOG, Dr Tina Tellum MD PhD, Professor Davor Jurkovic MD PhD FRCOG

Institute for Women's Health, University College Hospital, London, United Kingdom

References

1. McGrattan M, Murji A. One size does not fit all: a nuanced approach to surgical management of interstitial ectopic pregnancy. Fertility and Sterility 2021, in press
2. Ackerman TE, Levi CS, Dashefsky SM, Holt SC, Lindsay DJ. Interstitial line: sonographic finding in interstitial (cornual) ectopic pregnancy. Radiology 1993;189: 83-87.
3. Diagnosis and Management of Ectopic Pregnancy: Green-top Guideline No. 21. BJOG 2016;123: e15-e55.
4. Terminology for describing normally sited and ectopic pregnancies on ultrasound: ESHRE recommendations for good practice. Hum Reprod Open 2020 Dec 16;2020(4):hoaa055.
5. Grant A, Murji A, Atri M. Can the presence of a surrounding endometrium differentiate eccentrically located intrauterine pregnancy from interstitial ectopic pregnancy? J Obstet Gynaecol Can 2017;39:627-634.
6. Doubilet PM, Benson CB, Bourne T, Blaivas M, Barnhart KT, Benacerraf BR, Brown DL, Filly RA, Fox JC, Goldstein SR et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med 2013;369(15):1443-51.