Abstract
Objectives: Interstitial ectopic pregnancy and pregnancy in a
rudimentary horn of a unicornuate uterus are rare forms of ectopic pregnancy but carry a high risk for maternal morbidity
and mortality. Their diagnosis is challenging and can be misdiagnosed with less dangerous conditions; namely: angular pregnancy or pregnancy in one side of septate or bicornuate uterus.
This study aimed to differentiate between these four situations
to allow early detection that will enhance the prognosis.
Methods: This is a retrospective study, carried out on 26 patients referred to a private referral center for obstetric and gynecology sonography, in the period from November 2019 till
November 2020. All cases were referred due to unusual eccenteric location of the gestational sac. In each case we assessed
3 variables using 2D -TVUS which were: relation to the endometrium , interstitial line sign and condition of the overlying
myometrium. We assessed also 2 variables using 3D- TVUS
which were: shape of the uterine cavity and the relation of the
gestational sac to the uterotubal junction.
Results: It was found that the gestational sac (GS) is within
the endometrium in angular pregnancy and pregnancy in septate and bicornuate uterus while GS is outside the endometrial interface in interstitial ectopic pregnancy and pregnancy in
rudimentary horn of unicornuate uterus. The interstitial line
sign was +ve and the overlying myometrium was thin only in
interstitial ectopic pregnancy. Cavity was normal in angular
and interstitial ectopic pregnancy but it has a Mullerian fusion
anomaly in cases of pregnancy in rudimentary horn of a unicornuate uterus and cases with pregnancy in one side of a septate
or bicornuate uterus. GS was lateral to the uterotubal junction
in interstitial ectopic pregnancy and pregnancy in rudimentary
horn of unicornuate uterus but it was medial to it in the other 3
situations.
Conclusion: Our study described a simple triaging model based
on sonographic criteria for four pregnancy situations where the
gestational sac appears eccenterically in the early 1st trimester.
These four situations are namely; interstitial ectopic pregnancy,
ectopic pregnancy in a rudimentary horn of a unicornuate uterus,
angular pregnancy and pregnancy in one side
of a septate or bicornuate uterus. This model
will be helpful for early accurate diagnosis to
avoid false positive diagnosis that may lead to
unnecessary intervention and false negative
diagnosis that may lead to maternal morbidity
or mortality.