A bicornuate uterus is a type of congenital uterine malformation (müllerian duct abnormality). A bicornuate uterus is heart-shaped with two joined cavities whereas a typical uterus has a single cavity.
Causes of a Bicornuate Uterus:
A bicornuate uterus results from the uterus not forming properly in a woman's early prenatal development. This can happen to women whose mothers took a medication called DES during pregnancy, or it can happen for unknown reasons.
Diagnosing Bicornuate Uterin:
Doctors can get an idea of whether a woman has a bicornuate uterus by using a hysterosalpingogram (HSG) or a hysteroscopy, but diagnosis should be confirmed with a three-dimensional ultrasound or laparoscopy (see below).
Bicornuate Uterus and Pregnancy Loss Risks:
Most studies find that the primary risk associated with a bicornuate uterus is of preterm labor and possible cervical insufficiency (not first-trimester miscarriages). Cervical insufficiency and preterm delivery could potentially cause a second-trimester miscarriage or loss at birth if the baby is born too prematurely, such as before 24 or 25 weeks of pregnancy (the point at which a premature baby can potentially survive).
However, many women with bicornuate uteri carry pregnancies to full term without any problems, so the risk may vary for each woman.
Treating a Bicornuate Uterus:
Some sources recommend reconstructive laparoscopic surgery of bicornuate uteri, but in most cases doctors do not suggest surgical treatment. Some women may need a cervical cerclage, a stitch placed in the cervix to stop premature dilation, which is what can cause premature delivery and possible late pregnancy loss. Treatment depends on the physician and the circumstances of each situation.
Why Confirming the Diagnosis May Be Important for Women With Miscarriages:
Particularly for women with recurrent miscarriages, it’s important to note that there is a documented trend that women who actually have septate uteri are sometimes misdiagnosed as having bicornuate uteri. The two congenital uterine malformations can look similar on imaging studies, such as HSG or ultrasound, but they differ in that a septate uterus is round on the top with a single cavity in the uterus and a bicornuate uterus dips on the top, forming a heart shape with two cavities.
Why is this important? For starters, the treatment is different –- a bicornuate uterus might not be treated at all except to watch for signs of cervical dilation. And if it is treated surgically, the treatment is a reconstruction via laparoscopy. Whereas a septate uterus is usually treated through a hysteroscopic surgery. In addition, a bicornuate uterus is often not considered a factor in recurrent miscarriages, whereas a septate uterus is known to increase miscarriage risks.
For these reasons, if you are having recurrent miscarriages and your doctor has diagnosed a bicornuate uterus through an imaging study, consider seeing a specialist for a second opinion to confirm the diagnosis and treatment plan.