Angular pregnancy occurs when a fertilized egg implants in an unusual location within the uterus, specifically in the upper, outer corner near where the fallopian tube connects. While technically inside the uterus, this eccentric placement can lead to unique considerations for pregnancy safety and progression. This article clarifies the nature of angular pregnancy and its potential implications.
Understanding Angular Pregnancy
Angular pregnancy occurs when the blastocyst implants in the lateral angle of the endometrial cavity, medial to the uterotubal junction. This distinguishes it from a typical intrauterine pregnancy, which implants more centrally. While some medical guidelines suggest “eccentric intrauterine pregnancy,” “angular pregnancy” remains widely used for this specific off-center implantation.
It is important to differentiate angular pregnancy from an interstitial pregnancy, a form of ectopic pregnancy. An interstitial pregnancy implants within the muscular wall of the fallopian tube as it courses through the uterine wall, making it a true ectopic pregnancy. In contrast, an angular pregnancy is an intrauterine implantation because the gestational sac remains within the endometrial cavity, though eccentrically located. A “cornual pregnancy” refers to a pregnancy developing in a malformed uterus, such as in one horn of a bicornuate uterus.
Potential Complications and Risks
Angular pregnancy carries a higher risk of complications due to its specific location. The implantation site in the uterine angle may have a thinner myometrial layer, the muscular wall of the uterus. This layer can stretch and thin as pregnancy progresses, increasing the risk of uterine rupture, where the uterine wall tears and can lead to severe internal bleeding. Ruptures have been reported even in early gestation.
Significant bleeding can arise from the implantation site, potentially leading to substantial blood loss. There is also an increased likelihood of placental retention, where the placenta does not detach completely after birth, and postpartum hemorrhage. For the fetus, potential adverse outcomes include growth restriction and preterm birth, possibly due to the compromised implantation site and blood supply.
Identifying and Diagnosing Angular Pregnancy
Identifying an angular pregnancy can be challenging because its symptoms often resemble those of a typical early pregnancy. Some individuals may experience non-specific symptoms such as abdominal pain or vaginal bleeding. Due to its intrauterine nature, these symptoms might appear later in gestation compared to true ectopic pregnancies.
Diagnosis primarily relies on transvaginal ultrasound imaging to visualize the precise location of the gestational sac within the uterus. Key features include an eccentrically located gestational sac in the lateral angle of the uterus, positioned medially to the uterotubal junction. Providers also assess the myometrial thickness surrounding the sac, as a thinned myometrial layer can be an indicator. Three-dimensional ultrasound can be helpful in providing a clearer visualization. Serial measurements of human chorionic gonadotropin (hCG) levels may also be used to monitor pregnancy progression, though they are not diagnostic on their own.
Treatment and Monitoring
Management of an angular pregnancy is individualized, depending on gestational age, symptom severity, and the patient’s overall health. In some cases, particularly when diagnosed early and without significant symptoms, close monitoring (expectant management) may be considered. Studies have shown positive outcomes with expectant management for asymptomatic cases, suggesting not all angular pregnancies lead to severe complications.
Medical management, such as methotrexate, has limited applicability and higher failure rates for angular pregnancies compared to other ectopic pregnancies. For symptomatic cases or those with increasing risk, surgical interventions are the primary treatment. These may involve laparoscopic or open surgery to remove pregnancy tissue and repair the uterine wall, aiming to preserve uterine integrity. The goal of any treatment strategy is to prevent severe complications, especially uterine rupture and hemorrhage.
Outlook and Future Considerations
With early diagnosis and appropriate monitoring, many angular pregnancies can result in successful live births. After treatment or delivery, thorough follow-up care is important for the mother’s recovery, including monitoring for any residual tissue or complications.
Individuals who have experienced an angular pregnancy may have an increased risk of recurrence in subsequent pregnancies, possibly due to unique uterine anatomy. Therefore, in future pregnancies, early and careful ultrasound monitoring is recommended to identify the implantation site promptly and manage potential risks effectively.