Although the term 'interstitial' and 'cornual' ectopic pregnancies are used interchangeably, there is a specific difference
- an interstitial pregnancy refers to an ectopic location of the gestational sac in the intramyometrial segment of the fallopian tube in a normally configured uterus
- an interstitial pregnancy should also be differentiated from an angular pregnancy
- an angular pregnancy occurs when an embryo gets implanted in the lateral angle of the uterine cavity, medial to the internal ostium of the fallopian tube
- a cornual pregnancy pertains to an ectopic location of the gestational sac in the cornu of a bicornuate uterus
Prevalence of congenital uterine malformations is about 6-7% in the female population and higher in women with reproductive problems
- bicornuate uterus is an abnormality with a partial nonfusion of the Müllerian duct resulting in a central myometrium that can extend as far down as the internal cervix opening. This malformation makes up approximately 3% of the uterine malformations (1)
- malformation in itself is asymptomatic but is associated with an increased rate of reproductive problems including repeated late abortions or miscarriages (2)
Prevalence of interstial/cornual pregnancies
- most common location of the ectopic pregnancies continues to be fallopian tubes (accounting for roughly 95% of all the ectopic pregnancies), followed by the far less common interstitial ectopic pregnancies which comprise 2-4% of all the extrauterine cavity pregnancies (3)
An interstitial ectopic pregnancy is a rare and a dangerous form of an ectopic pregnancy. It presents late clinically and it is difficult to be imaged radiographically.
Notes:
- interstitial part of the fallopian tube is the proximal portion that lies within the muscle wall of the uterus. It is 0.7 mm wide and 1-2 cm long, with a slightly tortuous course upwards and outwards from the uterine cavity (4).
Reference:
- Saravelos SH, Cocksedge KA, Li TC. Prevalence and diagnosis of congenital uterine anomalies in women with reproductive failure: a critical appraisal. Human Reproduction Update. 2008;14(5):415-429.
- Rackow BW, Arici A. Reproductive performance of women with müllerian anomalies. Current Opinion in Obstetrics and Gynecology. 2007;19(3):229-237.
- Tulandi T, Al-Jaroudi D. The interstitial pregnancy :results which were generated from the Society of Reproductive Surgeons Registry. Obstet Gynaecol. 2004;103:47-50.
- Te Linde's Operative Gynaecology. Ninth. Ectopic pregnancy.