Evidence Matters

Is there a Left-Right Asymmetry of Tubal Pregnancies?

BACKGROUND AND PURPOSE:

There have been reports in the literature that ovulation is more frequent in the right ovary and fertility from oocytes derived from the right ovary may be superior to those on the left
While research is available related to ovulation, there is minimal data on whether there is similar asymmetry in the setting of ectopic pregnancy
Wei Xia et al. (JMIG, 2018) investigated whether there are left-right asymmetries in tubal pregnancies (TP)

Retrospective study (2005-2016)
Participants
- Women diagnosed with ectopic pregnancies
Data collection included
- Demographic characteristics | Reproductive, gynecological and surgical history | Clinical features such as abdominal pain and hCG levels | Treatment

6,186 patient charts with TP were included
The overall frequency of right-sided TP was 54.48% (3,370/6,186)
- Significantly higher than the expected 50% (P <0.001)
The proportion of right-sided TP
- Decreased with age (P for trend = 0.007)
- Decreased from the proximal (interstitial) end to the distal (fimbrial) end of the tube (P for trend = 0.017)
If a corpus luteum was present, it was
- More common on the right ovary (P <0.001)
- Located in the contralateral ovary to the TP side in 41.38% of cases
Tubal rupture more frequent in left TP (4.26%) vs right TP (2.94%); (P = 0.005)

The authors recognize the limitations of this study, specifically retrospective design that would allow for biases
This study did detect right sided asymmetry/dominance in ectopic (tubal) pregnancies
Clinical feature differences were also observed, with more frequent tubal ruptures in left side TP
Underlying mechanisms still unknown, but authors hypothesize that
- Right sided ovulation appears more frequent
- There is a difference between left (left renal vein) and right ovarian (IVC) venous drainage

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