Anatomic Factors in Recurrent Pregnancy Loss

Anne S. Devi Wold, MD; Norma Pham, MD; Aydin Arici, MD

Disclosures

Semin Reprod Med. 2006;24(1):25-32. 

In This Article

Acquired Uterine Abnormalities

Intrauterine Adhesions

Intrauterine trauma resulting from vigorous endometrial curettage or postabortal endometritis is a common instigator for the development of adhesions. Intrauterine synechiae or Asherman syndrome is an acquired uterine defect that has been associated with RPL. The severity of adhesions may range from minimal to complete ablation of the endometrial cavity. These adhesions are thought to decrease the volume of the uterine cavity, and may interfere with the normal placentation and lead to pregnancy loss.

The reproductive outcomes of women with Asherman syndrome are generally poor. In the absence of treatment, approximately 40% of pregnancies in these women appear to end in spontaneous abortion and another 23% result in preterm deliveries.[40] Hysteroscopic surgical excision of intrauterine adhesions appears to reduce subsequent pregnancy loss and appears to be superior to blind lysis of adhesions with a curette.[15]

Intrauterine Cavity Abnormalities

Intrauterine cavity abnormalities, such as leiomyomas and polyps, can contribute to pregnancy loss. Myomas are the most common benign tumor in women of reproductive age, affecting 20 to 50% of this population.[11] They are classified according to their anatomical location within the uterus and may be described as subserosal, intramural, and submucosal. Fibroids are considered subserosal if they are located beneath the serosa and if > 50% of the tumor is found protruding out of the serosal surface. If less than 50% protrudes and if the fibroid is located within the myometrium, it is considered intramural. Submucosal fibroids protrude into the uterine cavity and are located adjacent to the endometrium.

There are several hypotheses regarding how fibroids may be associated with RPL. Depending on the fibroid size and location, it may partially obliterate or alter the contour of the intrauterine cavity. It may also provide a poorly vascularized endometrium for implantation or compromise placental development. Uterine fibroids and polyps may also act like an intrauterine device, causing subacute endometritis, and therefore, impair the migration of sperm, ovum, or embryo.[41] Until recently, it was believed 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 myomas in the range of 30 mm.[42] When smaller myomas are identified, it is unclear if myomectomy is beneficial.[43]

In a retrospective study, Li et al[41] concluded that uterine fibroids are associated with a high rate of overall pregnancy loss by determining that women with fibroids had a 60% rate of miscarriage, which after myomectomy was reduced to 24%. Similarly, in another retrospective study, Marchionni et al[44] evaluated 72 patients with unexplained infertility and intramural and subserosal myomas who underwent abdominal myomectomy. The majority of subjects had one to five myomas, size ranged from 3 to 8 cm, and no details were provided about preoperative uterine cavity evaluation. Statistically significant differences were found between preoperative and postoperative conception rates (28 versus 70%), live birth rates (30 versus 75%), and miscarriage rates (69 versus 25%). The authors commented that abdominal myomectomy significantly improved reproductive outcomes in this series, especially if a single myoma was removed, and neither myoma size nor location was a significant factor impairing fertility.

Hysteroscopic myomectomy has been used to treat women with submucous fibroids, infertility, and RPL.[15,45] It is the procedure of choice in women with submucous fibroids because the abdominal approach has been associated with longer anesthesia time, higher blood loss, higher risk of postoperative adhesion formation and infection, and the need for elective cesarean sections in subsequent pregnancies.[15,45]

Uterine artery embolization (UAE) has been used successfully to treat women with symptomatic fibroids; however, the lack of its long-term effect on fertility has made it unattractive to women wishing to conceive. In a study comparing UAE versus laparoscopic myomectomy, Goldberg et al[46] found that pregnancy after UAE had a higher incidence in malpresentation and preterm labor. Spontaneous abortions were also similarly higher but the difference was not statistically significant. Thus, myomectomy should be considered in women with submucosal or intramural leiomyoma presenting with RPL.

Cervical Incompetence

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 trimester. It may be associated with congenital uterine abnormalities such as septate or bicornuate uterus. Rarely, it may be congenital following in utero exposure to DES.[38] However, the majority of cases occur as a result of surgical trauma to the cervix from conization, loop electrosurgical excision procedures, overdilation of the cervix during pregnancy termination, or obstetric lacerations.[47]

Transvaginal ultrasound has been shown to be a reproducible and safe method to assess cervical length in pregnancy in women with obstetrical history suggestive of cervical incompetence.[48,49] The cervical length, however, has a wide range before twenty weeks of gestation. The median cervical length is 35 to 40 mm from 14 to 22 weeks and decreases to approximately 35 mm between 24 and 28 weeks, and 30 mm after 32 weeks.[49] Although a short cervix does not appear to itself indicate cervical incompetence, serial ultrasound examinations starting between 16 and 20 weeks of gestation are considered in women with second-trimester losses and preterm deliveries. Cerclage is often considered in the presence of cervical shortening and/or funneling and in the absence of chorioamniotis.[50] In addition, women with a history of three or more midtrimester pregnancy losses or preterm deliveries may be candidates for elective cerclage.[51]

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