Early Pregnancy Loss: Anatomic Causes

Anatomic uterine defects are known to cause obstetric complications, including recurrent pregnancy loss, preterm labor and delivery, and malpresentation. Therefore, a uterine malformation should be considered in any woman with recurrent pregnancy loss. However, not all women with abnormal uteri have obstetric complications. Impaired vascularization and fetal growth restriction due to uterine distortion are 2 commonly discussed reasons for pregnancy loss.

The incidence of uterine anomalies is estimated to be 1 per 200-600 women, depending on the method used for diagnosis. When manual exploration is preformed at the time of delivery, uterine anomalies are found in approximately 3% of women. However, in women with a history of pregnancy loss, uterine abnormalities are present in approximately 27%.

Uterine müllerian anomalies

The most common uterine defects include septate, bicornuate, and didelphic uteri. The unicornuate uterus is least common. Bicornuate and unicornuate uteri are frequently associated with second-trimester loss and preterm delivery. The highest rate of reproductive losses are found in bicornuate uteri (47%) compared with unicornuate uteri (17%). Malpresentation and fetal growth restriction are other complications that women with unicornuate uteri face. Women with unicornuate and didelphys uteri have the highest rate of abnormal deliveries, while women with uterine septa have a 26% risk of reproductive loss.

In addition to müllerian anomalies, other anatomic causes of recurrent pregnancy loss to consider for include diethylstilbestrol exposure related-anomalies, Asherman syndrome, incompetent cervix, leiomyomas, and uterine polyps.

Controversies exist among these listed uterine anatomic abnormalities as causes for pregnancy loss. They are suggested but not scientifically proven potential causes.

Management

Imaging studies of choice include hysteroscopy, hysterosalpingography (HSG), and vaginal ultrasonography. Findings may be confirmed with MRI. For instance, a banana-shaped cavity with a single fallopian tube is the most common finding in a unicornuate uterus. Prophylactic cervical cerclage should be considered in patients with a unicornuate uterus. Some authors support expectant management in these patients, with serial assessments of cervical lengths by using digital and ultrasonographic examinations.

Surgical correction of uterine anatomic abnormalities has not been shown to benefit pregnancy outcomes in a prospective controlled trial. However, data from uncontrolled retrospective reviews have suggested that resection of the uterine septum increases delivery rates (70-85% in 1 study).