A heart-shaped uterus, medically known as a bicornuate uterus, is a congenital anomaly classified as a Müllerian duct anomaly. This variation occurs when the two ducts that normally fuse to form the uterus in a female fetus do not fully join together. This incomplete fusion results in a reproductive organ that deviates from the typical pear shape, presenting with a distinct indentation at the top. The condition affects a small percentage of the general female population.
Anatomy of the Bicornuate Uterus
The characteristic heart shape is defined by a deep cleft or indentation at the top of the uterus, known as the fundus. This structure results in the uterine cavity being partially divided into two “horns,” or cornua, giving the organ a two-pointed appearance. The depth of this division varies among individuals, ranging from a slight dip to a near-complete separation of the upper uterine body.
While the upper portion is split, the lower parts of the reproductive tract, including the cervix and the vagina, typically fuse normally and remain singular. This anatomical division is a direct result of the Müllerian ducts failing to completely merge during fetal development. It is important to distinguish a bicornuate uterus from a septate uterus. The bicornuate uterus is defined by its external cleft, usually greater than one centimeter deep, while the septate uterus has a normal external contour but an internal wall dividing the cavity.
How the Condition is Diagnosed
A diagnosis of a bicornuate uterus often occurs incidentally during fertility investigations or routine pelvic imaging. Initial detection frequently happens via a standard transvaginal or abdominal ultrasound, which visualizes the organ’s external contour and internal split. However, ultrasound alone can sometimes struggle to definitively differentiate a bicornuate uterus from a septate uterus, which is a crucial distinction for treatment planning.
To confirm the diagnosis and assess the full extent of the anomaly, specialized imaging techniques are employed. Hysterosalpingography (HSG) uses a contrast dye to map the internal uterine cavity, revealing the divergence of the two horns. Three-dimensional pelvic Magnetic Resonance Imaging (3D MRI) is considered the most reliable tool, providing high-resolution images of both the internal cavity and the external uterine surface for precise measurement of the fundal cleft.
Pregnancy Risks and Outcomes
Although conception is not impaired by a bicornuate uterus, carrying a pregnancy to term is the main concern associated with the condition. The reduced internal volume and irregular shape of the uterine cavity limit the space available for the growing fetus. This restriction can compromise blood supply to the developing placenta and restrict fetal movement and growth.
Women with this anomaly face an elevated risk of adverse pregnancy outcomes, particularly second-trimester miscarriage and preterm birth, defined as delivery before 37 weeks of gestation. The irregular structure can also lead to issues with fetal positioning, as the baby may not have enough room to turn into the head-down position. This often results in fetal malpresentation, such as a breech presentation, which frequently necessitates a cesarean section for delivery. Furthermore, the condition is associated with a higher likelihood of intrauterine growth restriction (IUGR), where the fetus does not grow to its full potential weight.
Treatment and Management
For most women who have not experienced recurrent pregnancy loss, the condition is managed conservatively with close medical surveillance during pregnancy. Increased monitoring with frequent ultrasounds is recommended to watch for signs of complications, such as cervical insufficiency or the onset of preterm labor. Early detection allows for timely intervention to prolong the gestation period.
Surgical correction, known as metroplasty, is rarely performed unless a woman has a history of multiple late-term miscarriages or preterm deliveries linked to the anomaly. The most common procedure is the Strassman metroplasty, which involves surgically unifying the two uterine horns into a single, larger cavity. This procedure has demonstrated high success rates in improving live birth rates for selected patients. Following this surgery, subsequent deliveries must be performed via cesarean section to mitigate the risk of uterine rupture.