ANATOMIC CAUSES OF RPL
Congenital and acquired anomalies of the uterus are a major correctable cause of RPL. Anatomic causes of RPL are typically diagnosed using hysterosalpingography or sonohysterography. Hysteroscopy, laparoscopy, or magnetic resonance imaging can supplement these tests as needed. Recently, transvaginal three-dimensional ultrasonography has been introduced and has allowed an accurate and non-invasive diagnosis of congenital uterine anomalies. The prevalence of congenital and acquired uterine anomalies in 904 women with RPL was reported by our group in 2013 and published in Fertility and Sterility. The summary of the abnormalities that were found in women with RPL is detailed in the table below. Primary RPL is when there have never been any live born children. Secondary RPL is when there has been at least one live born child.
Table. Frequency of Uterine anomalies in primary and secondary RPL Patients
% Occurrence (n)
|Secondary RPL (n=304)
% Occurrence (n)
|Congenital Anomalies Total||8.5 (51)||13.8 (42)||0.003|
|Bicornuate Uterus||1.2 (7)||0||0.102|
|Didelphic Uterus||0.2 (1)||0.3 (1)||1.000|
|Septate Uterus (> 10 mm depth)||5.8 (35)||2.6 (8)||0.032|
|T-shaped Uterus||0.5 (3)||0||0.555|
|Unicornuate Uterus||0.8 (5)||0.3 (1)||0.670|
|Acquired Anomalies Total||14.5 (87)||10.9 (33)||0.146|
|Adhesions (in upper 2/3 of cavity)||3.7 (22)||4.9 (15)||0.337|
|Fibroids (submucosal or distorting cavity)||7.8 (47)||3.6 (11)||0.014|
|Polyps (> 1 cm)||3.7 (22)||2.3 (7)||0.322|
|Congenital and Acquired Anomalies Total||22.3 (134)a||13.8 (42)||0.002|
a Five patients had both congenital and acquired anomalies.
Congenital malformations of the reproductive tract result from failure to complete bilateral duct elongation, fusion, canalization, or septal resorption of the Müllerian ducts. Müllerian anomalies were found in 6-10% of women two or more consecutive spontaneous miscarraiges who underwent hysterosalpingography or hysteroscopic examination of their uteri The most common congenital abnormality associated with pregnancy loss is the septate uterus. The spontaneous miscarriage rate is high, averaging about 65% of pregnancies in some studies. A septum was found in significantly more frequently in women with primary RPL than women with secondary RPL in our recent study . Uncontrolled studies suggest that resection of the uterine septum results in higher delivery rates than in women without treatment. Other congenital abnormalities, such as uterine didelphys, bicornuate and unicornuate uterus are more frequently associated with later trimester losses or preterm delivery.
Sonohysterograms of normal and abnormal uterine shapes.
Intrauterine trauma resulting from endometrial curettage or endometritis is associated with a risk for the development of adhesions. Intrauterine adhesions (synechiae) are an acquired uterine defect that has been associated with recurrent miscarriage. The severity of adhesions may range from minimal to complete ablation of the endometrial cavity. The term Asherman’s syndrome is often used to describe intrauterine adhesions associated with oligomenorrhea or amenorrhea and are thought to interfere with the normal placentation and are treated with Minimally Invasive Surgery such as a hysteroscopic resection.
Intrauterine cavity abnormalities, such as submucosal leiomyomas and polyps, can contribute to pregnancy loss. Depending on the leiomyoma size and location, it may partially obliterate or alter the contour of the intrauterine cavity, providing a poorly vascularized endometrium for implantation or otherwise compromising placental development. Uterine leiomyomas and polyps may also act like an IUD, causing subacute endometritis. Until recently, it was felt that only submucous leiomyomas should be surgically removed prior to subsequent attempts at pregnancy. However, several recent studies investigating the implantation rate in women undergoing in vitro fertilization have clearly demonstrated decreased implantation with intramural leiomyomas in the range of 30 mm . Minimally invasive surgical options are available for correction of intrauterine masses.
Cervical incompetence can be considered as an acquired uterine anomaly that is associated with RPL. The diagnosis of cervical incompetence is based on the presence of painless cervical dilation resulting in the inability of the uterine cervix to retain a pregnancy. Cervical incompetence commonly causes pregnancy loss in the second, rather than first, trimester. It may be associated with congenital uterine abnormalities such as septate or bicornuate uterus. It is postulated that most cases occur as a result of genetic deficiencies of the cervix, surgical trauma to the cervix from conization, loop electrosurgical excision procedures, or obstetric lacerations.