Bicornuate uterus: A rare case of a viable full term pregnancy in the right uterine horn

Abstract

Bicornuate uterus is a rare congenital uterine malformation and structural abnormality that affects less than 05 % of women in the United States. Resulting pregnancies are rarely carried to term and commonly result in fetal abnormalities and complications such as decreased fertility and risks of complicated pregnancies such as spontaneous abortion and miscarriages, IUGR, preterm delivery, cervical incompetence, and fetal malpresentations. This report highlights a case in which a 32-year-old patient with a bicornis bicollis uterus who had a viable pregnancy in one of the uterine horns later delivered a live male neonate at term without complications via spontaneous vaginal delivery (SVD). The study underscores the importance of using the imaging modalities of ultrasonography, magnetic resonance imaging, and hysterosalpingograms to aid in the diagnosis and monitoring throughout the duration of the pregnancy.

Introduction

Uterine malformations are seen in about 7%-10% of women in the general population [1]. They result from either the abnormal formation or fusion of the para-mesonephric and mullerian ducts, or dissolution of the septum during embryonic life, resulting in a variety of congenital uterine malformations. The development of the ducts is highly regulated by a wide array of signaling molecules and gene expression, including include PAX2, EMX2, HOXA13, Wnt, and LIM1 [2]. The anomalies of the Mullerian system are classified into 8 main groups, denoted by class I to VIII and represented chronologically by the most to least severe. They include mullerian agenesis (I), the failure of both ducts to form, unicornuate uterus (II), the failure of 1 duct to form, uterus didelphys (III), the complete failure of fusion, bicornuate uterus (IV), the failure of incomplete fusion cranially, septate uterus (V), the failure of complete septum dissolution and resorption, arcuate uterus (VI), an iconsequential septum, DES (T-shaped) uterus (VII), a resulting feature of the DES teratogen, and other (VIII) [3]. The bicornuate uterus can be subdivided into bicornis bicollis uterus and bicornis unicollis uterus, which are classified by a division at the external cervical os and above the external cervical os, respectively. The bicornuate uterus accounts for approximately 10% of the mullerian anomalies [1].

Pregnancies occurring in the malformed uterus are relatively rare, with many of them presenting as asymptomatic. Uterine malformations should be suspected in patients with recurrent miscarriages and malpresentations [4]. About 15%-25% of women with uterine anomalies encounter difficulties with fertility and reproduction [5]. These patients typically have increased incidence of miscarriage (25%), preterm birth (15%-25%), or cervical insufficiency (38%) [6]. Other outcomes include poor fetal growth, malpresentations, and abnormal placental and ectopic pregnancies [5,6]. However, although less common, some pregnancies may be carried to term [6].

The diagnosis of uterine malformations such as a bicornuate uterus requires radiologic diagnostic modalities like ultrasound, magnetic resonance imaging (MRI), Hysterosalpingogram (HSG), and saline sonohysterography for an accurate diagnosis [7], [8], [9], [10].

Here, we present a case of a 32-year-old patient with a bicornis bicollis uterus who had a viable pregnancy in one of the uterine horns and later delivered a live male neonate at term via spontaneous vaginal delivery (SVD).

Case report

A 32-year-old Nigerian female G₃P₀⁺² (G3P0020) presented to the gynecology department with an eight-week history of amenorrhea and lower abdominal pain. She has been sexually active with the same partner for the last 3 years. She had a history of 2 miscarriages in the last 2 years at 10 and 12 weeks, respectively. However, previous obstetric scans that were obtained from private facilities during the prior pregnancies were reported as normal. Her age at menarche was 14 years and past menstrual history was uneventful. She denied any history of diabetes, hypertension, or Rh incompatibility. On examination she was found to be anicteric, afebrile, acyanotic, and in no form of apparent distress. Her pulse (72 bpm), blood pressure (110/80 mm Hg), and hematocrit (36%) were all normal at the time of presentation. Speculum examination revealed 2 cervices with a visible external cervical os on the right and a dimple on the left. Pregnancy in a patient with a bicornuate uterus was confirmed.

The obstetric ultrasound revealed 2 uterine horns and 2 cervices (Fig. 1). The right uterine horn was gravid and measured to be 11.4 cm x 5.6 cm. It contained a gestational sac with a fetal pole within it (Fig. 2) that exhibited cardiac activity. The myometrium of the right uterine horn showed uniform and normal myometrial echoes (Fig. 2). The gestational age of the fetal pole was 7 weeks and 6 days. The left uterine horn was empty and measured to be 8.4 × 3.7 cm (Fig. 3). The left horn revealed normal endometrial echoes, however, there was an oval shaped hypoechoic structure that was casting venetian shadows seen in the anterior myometrium near the fundus indicative of a fibroid (Fig. 3). The fibroid measured 1.8 cm x 1.9 cm. There was also an oval shaped, thin-walled anechoic structure seen within the right ovary with posterior acoustic enhancement consistent with a cyst. It measured 4.9 cm x 4.7 cm x 4.7 cm with an estimated volume of 56 mL (Fig. 4). The patient declined to undergo hysterosalpingography (HSG) after delivery of her child.

Fig. 1.

(A) and (B). Transverse B mode ultrasound scans at higher (A) and lower (B) levels of the pelvis showing the urinary bladder and 2 uterine horns and cervices. The right horn contains gestational sac with its respecitive fetal pole inside (bent arrow), while the left uterine horn is empty (block arrow). There is a depression (deep fundal cleft) between the 2 uterine horns (star) which can be seen in cases of a present bicornuate uterus.

Fig. 2.

Sagittal B-mode ultrasound of the pelvis showing the right uterine horn and cervix measuring 11.43 × 5.58 cm with a gestational sac (GS) its respective fetal pole inside (bent arrow). The myometrial echoes and the urinary bladder (star) are normal.

Fig. 3.

Sagittal B-mode ultrasound of the pelvis portraying the left uterine horn and cervix measuring 8.36 × 3.72 cm with a small fibroid (“f”) detected in the antero-fundal myometrium. The urinary bladder (star) and endometrial plate are normal.

Fig. 4.

Sagittal and transverse B-mode ultrasound of the pelvis showing an oval shaped, thin-walled anechoic structure (star) with posterior acoustic enhancement consistent with a cyst-likely a corpus luteal cyst, seen within the right ovary (block arrow). It measured 4.9 cm x 4.7 cm x 4.7 cm with an estimated volume of 56 mL.

The patient was advised to book her index pregnancy at the antenatal clinic, but she was noncompliant and subsequently presented in labor at term (38 weeks). At presentation, the symphysis fundal height (SFH) was measured to be 38 cm and commensurable with the gestational age. The external cervical os was 7 cm dilated and the fetal presenting region was cephalic. Her labor progressed and a 3.1 kg live male neonate was delivered an hour later via SVD.

Discussion

This case is a unique presentation of a bicornuate uterus in which the patient had a viable pregnancy that was carried to term and presented with interesting radiographic features. Given the rarity of this case and the variety of potential fetal complications that can result from this structural abnormality, it is crucial to understand its clinical presentation and manifestations on radiographic imaging throughout the pregnancy.

This case is a novel one as not many patients with bicornuate uterus can carry a healthy fetus to term and deliver via SVD. Moreover, understanding the radiographic findings and diagnostic modality of choice may guide radiologists and other clinicans to accurately evaluate as well as monitor both the mother and the fetus to yield a favorable prognosis. Although it presents less commonly than other etiologies for infertility and miscarriage, uterine malformations should be kept in mind for the differential diagnosis and initially suspected of patients with recurrent miscarriages and malpresentations [4].

Uterine abnormalities are due to anomalies or disturbances at the time of fusion and formation of the Mullerian or paramesonephric ducts or the dissolution of the septum during embryonic life [1,6]. A bicornuate uterus is a congenital uterine anomaly that results from the defective partially incomplete lateral fusion of the paramesonephric ducts at about the tenth week of intrauterine life around the fundus, leading to duplication of the uterus [6]. A bicornuate uterus consists of two symmetric horns that are fused inferiorly with communication of the endometrial cavities, most often at the level of the uterine isthmus [6]. Bicornuate uterus is estimated to represent 10% of Mullerian duct anomalies and occur in under 0.5% of females [10]. Pregnancies without subsequent complications occurring in the malformed uterus are relatively rare. Many affected women are asymptomatic, but the diagnosis should be suspected in patients with recurrent miscarriages and malpresentations. When asymptomatic and not presenting with multiple miscarriages, women with a bicornuate uterus may remain undiagnosed except when detected incidentally during routine pelvic scans or during abdominal and pelvic surgeries that are typically performed past childbearing years (ie, hysterectomies) [7].

The precise diagnosis of bicornuate uterus and other uterine anomalies requires radiologic diagnostic modalities such as ultrasonography (US), magnetic resonance imaging (MRI), hysterosalpingogram (HSG), and saline sonohysterography [7], [8], [9], [10]. Magnetic Resonance imaging and ultrasound should be primarily used to identify the presence of a deep fundal cleft [9] in presentations of a bicornuate uterus such as this case. US should be used as the baseline for detecting uterine abnormalities such as bicornuate uterus [7], making reliability on ultrasound the mainstay of initial assessment, especially in instances of associated pregnancy due to minimal risk. As seen in this case, divergent uterine horns and separation of uterine cavities may be optimally seen on US [11]. However, an MRI is considered to be the preferred modality due to its multiplanar capabilities and ability to evaluate the uterine contour, junctional zone, and other pelvic anatomical structures [9]. However, due to its high cost and the lack of resources at the Nigerian hospital, an MRI was not readily available. On MRI imaging, both uterine horns commonly have normal zonal anatomy. The appearance of a duplicated cervix, as denoted by “owl eyes”, is seen in patients with a bicornuate bicollis uterus [11].

In patients with a bicornuate uterus, HSG commonly demonstrates an opacification of 2 symmetric fusiform uterine cavities (horns) and fallopian tubes [11]. Historically, an intercornual angle of greater than 105° was used for diagnosis. However, imaging overlap with a septate uterus makes differentiation impossible during an HSG and pregnancy is a contraindication [11]. For this reason, an HSG was not performed for this patient as she was pregnant. Even though she did not give consent to undergo an HSG after delivery, it would normally assist in its diagnosis and prognostic value.

Women found to have a bicornuate uterus may experience a successful pregnancy outcome, such as in this patient, but are still at risk of obstetric complications such as fetal malpresentations, preterm rupture of membranes, small for gestational age fetuses, recurrent pregnancy losses, preterm deliveries, intra-uterine growth restriction (IUGR), and cervical incompetence [7].

In fact, other successful pregnancies in patients with a bicornuate uterus exist in literature. In 2013, a women diagnosed with bicornuate uterus in Ogbomoso was able to give birth to a live male infant weighting 2.8 kg [12]. However, it is important to note that the mother had 2 previous failed pregnancies: 1 failed pregnancy was an intrauterine fetal death at term and the other pregnancy ended in a spontaneous abortion at 12 weeks of gestation [12]. This illustrates that the diagnosis of bicornuate uterus doesn't guarantee infertility, however, the risk of poor pregnancy outcomes may be increased. In fact, numerous studies have been done to assess the reproductive performance in women with bicornuate uterus. In a study of 21 patients with bicornuate uterus it was found that the probability of giving birth to a live-born infant in patient with bicornuate uterus with no corrective surgery was 30%, 58% and 79% for the first, second and third pregnancy respectively [13].

Furthermore, in the aforementioned case, the male infant was born with bilateral forefoot abnormalities: the infant also had overriding of the second and fourth toes bilaterally, and mild pseudo-tallipes [12]. The abnormalities eventually resolved on its own [12]. The fetal limb deformity might have resulted from prolonged pressure on the limbs due to lack of space within the uterine horn where the fetal development took place [12]. This again illustrates the fact that while pregnancy with bicornuate uterus may be viable, there is still the added risk of deformities that may or may not go away on their own. It is therefore feasible to conclude that pregnant patients diagnosed with bicornuate uterus must be closely monitored and followed in order to provide the best possible care.

In conclusion, it is of utmost importance for clinicians such as OBGYNs, radiologists, and other members of the multidisciplinary health care team to be aware of the multitude of manifestations that occur in such a presentation and monitor through proper imaging as the pregnancy may be potentially viable and carried to term.

Ethical approval

This case report was conducted in accordance with the Declaration of Helsinki. The collection and evaluation of all protected patient health information was performed in a Health Insurance Portability and Accountability Act (HIPAA) compliant manner.

Patient consent

Written informed consent for publication was obtained from the patient described in the OGM case.