Recurrent Miscarriage: A Review

Abstract

pregnancy events [2]. Clinical miscarriages may be subdivided into early clinical pregnancy losses (before gestational week 12) and late clinical pregnancy losses (gestational weeks 12 to 21). The term miscarriage is preferred rather than abortion both by patients and physicians, although "spontaneous abortion" is still used in scientific literature [3,4].For more than 30 years, controversy has existed on the number of miscarriages required to define RM and when diagnostic testing is warranted [5] EpidemiologyEarly pregnancy loss is perhaps the most common obstetric complication, occurring in over two-thirds of human conceptions. Approximately 15 -20% of all clinically recognized pregnancies will end in a miscarriage [4,9,10]. However, prospective cohort studies using sensitive and specific daily urinary hCG assays in women trying to conceive have demonstrated that only around one-third of conceptions progress to a live birth. Most of the losses occur before the clinical recognition of pregnancy as implantation failures. An estimated 30% of human conceptions are lost prior to implantation and a further 30% following implantation but before the missed menstrual period, that is in the third or fourth week of gestation. These are often termed preclinical losses [11].The risk of sporadic miscarriage between 6 and 12 weeks of gestation in women less than 35 years of age is 9% to 12%. The risk increases with age. In women older than 40 years of age, the sporadic miscarriage rate approaches 50%. Late losses between 12 and 22 weeks occur less frequently and constitute around 4% of pregnancy outcomes [4,9].Compared to sporadic miscarriage the prevalence of RM is considerably lower irrespective of whether biochemical losses are included or not. Approximately 1% of all women trying to conceive have recurrent miscarriage, defined as three previous miscarriages; when recurrent miscarriage is defined as two previous miscarriages, the proportion rises to 3% [12,13]. EtiologyMultiple potential etiologies for RM have been described (Table 1). As a consequence, several recommendations have been published regarding the evaluation and management of RM [3].The potential etiologies of RM can be divided into embryologically driven causes (mainly due to an abnormal embryonic karyotype) and maternally driven causes which affect the endometrium and/or placental development [14,15]. Thus, studies that focus on RM have Barrenetxea G, et al., J Reprod Med Gynecol Obstet 2017 AbstractHuman reproduction is characterized by its inefficiency. The loss of pregnancy at any stage can be a devastating experience and particular sensitivity is required in assessing and counseling couples with Recurrent Miscarriage (RM). Recurrent Miscarriage (RM) represents a clinical challenge for physicians not only because there are multiple possible etiologies, but also because the diagnostic testing is costly and time consuming. Despite several well-known etiologic factors, the cause of RM cannot be determined in almost 50% of cases. Multiple potential etiolo...