The common term “heart-shaped uterus” describes the Bicornuate Uterus, a Müllerian duct anomaly. This congenital structural difference is characterized by an indentation at the top, dividing the organ into two distinct horns or cavities. This anomaly affects approximately 0.4% of females in the general population. While many individuals remain asymptomatic, this uterine shape can sometimes lead to complications, particularly concerning reproductive outcomes.
The Embryological Origin
The cause of the bicornuate uterus is a failure during the normal development of the female reproductive tract in the fetus. The uterus, fallopian tubes, and upper vagina develop from two parallel structures called the Müllerian ducts. These ducts are meant to fuse together and the separating wall should resorb, creating one single, smooth uterine cavity.
The bicornuate uterus results from the incomplete fusion of the upper segments of these two Müllerian ducts. This developmental failure typically occurs between the sixth and tenth weeks of gestation. Because the upper portions do not fully merge, the top of the uterus retains a separation, forming the characteristic deep indentation that resembles a heart. The severity of the shape, described as partial or complete, depends on how far down the incomplete fusion extends.
How Doctors Identify This Condition
Diagnosis of a bicornuate uterus often occurs incidentally during a routine pelvic examination or ultrasound. It is also frequently discovered when a patient is investigated for fertility issues or recurrent pregnancy loss. Although the condition may not cause symptoms outside of pregnancy, the unique shape can sometimes be found when searching for causes of pelvic pain or painful menstruation.
Doctors use advanced imaging techniques to distinguish the bicornuate uterus from other anomalies. Three-dimensional (3D) transvaginal ultrasound is a preferred initial method, providing detailed views of the uterine shape and contour. Magnetic Resonance Imaging (MRI) is also utilized for its ability to produce highly detailed images of the soft tissues, helping map the extent of the division.
A key diagnostic factor is the appearance of the outer contour, which must be concave or heart-shaped, with a fundal cleft typically deeper than one centimeter. Imaging like Hysterosalpingography (HSG) visualizes the two internal cavities but is less reliable for determining the outer contour. This differentiation is important: a bicornuate uterus has an abnormal external shape, while a septate uterus has a normal external shape but a divided internal cavity.
Pregnancy Risks and Outcomes
Fertility itself is usually not impaired, but the presence of a bicornuate uterus introduces several risks during pregnancy. The primary issue is the reduced internal space available for the developing fetus, which restricts growth and movement. Because of the two-horned structure, the uterus cannot expand as effectively as a typically-shaped uterus.
The restricted space and potential for reduced blood supply can lead to an increased risk of complications. These include recurrent pregnancy loss, especially in the second trimester, and a higher likelihood of preterm labor and delivery (birth before 37 weeks). Fetal malpresentation is also common, as the baby may not have enough room to turn into the head-down position. This often results in a breech or transverse lie, frequently necessitating a Cesarean section delivery. The irregular shape can also be linked to an increased risk of cervical insufficiency, where the cervix opens too early.
Surgical and Non-Surgical Management
For individuals who have not experienced adverse reproductive outcomes, the standard approach is expectant management. This non-surgical path involves close monitoring during pregnancy, including regular ultrasounds to track fetal growth, position, and the condition of the cervix. Early detection of potential issues allows for timely intervention.
When a woman has a history of recurrent miscarriages or severe pregnancy complications linked to the bicornuate shape, surgical correction may be considered. The procedure is known as a Strassman Metroplasty. This reconstructive surgery involves incising the tissue that divides the two horns and suturing the uterine muscle layers back together to create a single, larger cavity.
Strassman Metroplasty can be performed through an open abdominal incision or using minimally invasive laparoscopic techniques. The goal is to improve uterine capacity and integrity, increasing the chances of carrying a pregnancy to term. Following this unification procedure, subsequent pregnancies are almost always delivered via Cesarean section to prevent the risk of uterine rupture along the surgical scar.