Angular pregnancies are those in which implantation occurs eccentrically along the fundus of the endometrial cavity, along the lateral upper angle or cornua of the uterus.
In contrast to interstitial tubal pregnancy, angular pregnancies have a more medial location and are considered an intrauterine implantation.
The term "angular pregnancy" is sometimes used interchangeably with "cornual pregnancy". This causes some ambiguity and the latter is best reserved for a pregnancy within a congenitally-anomalous uterus, such as one of the horns of a bicornuate, or the rudimentary corn of a unicornuate uterus.
Given the intrauterine location of angular pregnancies and the enveloping myometrium, these patients are likely to present with symptoms later than patients with ectopic pregnancies.
Angular pregnancy occurs when the blastocyst is implanted in the lateral angle of the endometrial cavity, medial to the uterotubal junction and round ligament 1.
The distinction is important because the developing embryo ovum of an interstitial pregnancy develops in the uterine wall, whereas in angular pregnancy it develops eccentrically within endometrial cavity and may be constrained within the cornua 1.
- 3D ultrasound can be helpful in the precise location of sac
- pregnancy is eccentrically high in location; the gestational sac is located within the endometrial cavity at the lateral upper angle on the spectrum between normal pregnancy and interstitial cornual pregnancies
- should always have normal myometrial coverage, which is thick and usually more than 5 mm
- grows towards the endometrial cavity and requires close follow-up to document the gestational sac growing into the cavity
Treatment and prognosis
Many of these pregnancies result in live birth but have an increased complication rate.
The true complication rate not known as cases reported as angular may have actually been interstitial but complications include:
- spontaneous abortion (~40%)
- uterine rupture (~15%)
interstitial ectopic pregnancy
- located in the intramural portion of Fallopian tube
- also eccentrically located with respect to endometrial cavity but seen separately >1 cm from the endometrial cavity
- interstitial line sign: an echogenic line in continuity from the ectopic to the endometrial echo complex
- covered by myometrium but thinned to <5 mm
- can grow to a larger size than the tubal ectopic pregnancy
- presents in settings of a uterine anomaly such as unicornuate, bicornuate, or septate uterus with a rudimentary horn
- gestational sac is located medial to the Fallopian tube including the anomalous part