OBJECTIVE: To describe the natural history and outcomes of a large cohort of expectantly managed angular pregnancies diagnosed in the first trimester by specific ultrasound criteria. METHODS: We conducted a prospective case series of women with prenatally diagnosed angular pregnancy at a single academic tertiary care center from March 2017 to February 2019. Participants were identified at first-trimester ultrasound scan using specifically proposed diagnostic criteria for angular pregnancy and followed prospectively. Maternal and fetal data were gathered from the medical record. RESULTS: Forty-two cases of angular pregnancy were identified at first-trimester ultrasound scan. At presentation, 33 patients (79%) were asymptomatic, eight (19%) had vaginal bleeding, and two (5%) had pain. The mean gestational age at diagnosis was 7.4±1.0 weeks; the mean myometrial thickness was 5.1±1.6 mm (95% CI 4.6–5.6). At initial follow-up about 2 weeks later, 23 patients (55%) had ultrasound scans that normalized, 13 (31%) cases persisted as angular pregnancies, and six (14%) resulted in early pregnancy loss. After each gestation had been followed until completion, 33 (80%) pregnancies resulted in live birth and eight (20%) in early pregnancy loss. One patient was lost to follow-up. Of the 33 live births, 24 (73%) were vaginal deliveries, nine (27%) were cesarean deliveries, 27 (82%) were term deliveries, and six (18%) were preterm deliveries. There were no cases of uterine rupture, maternal death, abnormal placentation, or hysterectomy. CONCLUSIONS: In 42 cases of angular pregnancy diagnosed by first-trimester ultrasound examination, outcomes were largely positive, with an 80% live-birth rate and a 20% early pregnancy loss rate. Early diagnosis of angular pregnancy using the described criteria may represent an entity that more closely resembles a normal, noneccentric intrauterine pregnancy rather than an ectopic pregnancy. Therefore, most cases can be closely observed and efforts made to expectantly manage pregnancies while awaiting viability.

Eccentrically located intracavitary pregnancies, which include pregnancies traditionally termed as cornual and/or angular, have long presented complex diagnostic and management challenges given their inherent relationship to interstitial ectopic pregnancies. This review uses the existing literature to discriminate among interstitial, cornual, and angular pregnancies. Current arguments propose the outright abandonment of the terms cornual and angular may be justified in favor of the singular term, eccentric pregnancy. Disparate definitions and diagnostic approaches have compromised the literature’s ability to precisely describe prognosis and ideal management practices for each of these types of pregnancies. Standardizing the classification of these pregnancies near the uterotubal junction is important to unify conservative, yet safe and effective management strategies. We advocate the use of early first trimester ultrasound to correctly differentiate between eccentric pregnancy and interstitial ectopic pregnancy as current research suggests substantially better outcomes with correctly diagnosed and expectantly managed eccentric pregnancies than past investigations may have shown. The expectant management of eccentric pregnancies will often result in a healthy term pregnancy, while interstitial ectopic pregnancies inherently have a poor likelihood of progressing to viability. When the terms and diagnosis of cornual, angular, and interstitial pregnancy are indistinct, there is substantial risk of intrauterine pregnancies to be inappropriately managed as ectopic pregnancies. Until we standardize terms and criteria, it will remain difficult, if not impossible, to determine true risk for pregnancy loss, preterm labor, abnormal placentation, and uterine or uterotubal rupture. The development of best practice guidelines will require standardized terminology and diagnostic techniques.

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The proposed human chorionic gonadotropin threshold model optimizes the balance between identifying viable intrauterine pregnancies and minimizing rates of misdiagnosis of nonviable pregnancies.