Superfertility and subfertility in patients with recurrent pregnancy loss: A comparative analysis of clinical characteristics and etiology based on differences in fertile ability.

This study aimed to elucidate the etiologies of and risk factors for recurrent pregnancy loss (RPL) according to fertile ability, focusing on the differences between superfertile and subfertile patients. This retrospective observational study included 828 women with RPL between July 2017 and February 2020. Patients were divided into three groups based on time to pregnancy (TTP): superfertile (SUP) (TTP ≤3 months for all previous pregnancies), subfertile (SUB) (previous TTP ≥12 months and use of assisted reproductive technology [ART]), and Normal (N) (TTP >3 or <12 months without ART). All patients were assessed for uterine anatomy, antiphospholipid antibodies (APAs), thyroid function, and thrombophilia. Of the 828 patients, 22%, 44%, and 34% were assigned to the SUP, SUB, and N groups, respectively. The mean ages were 33.9, 38.2, and 35.9 years in the SUP, SUB, and N groups, respectively, revealing a significant difference (P < 0.001). The anti-CL β2GPI antibody positivity rate was significantly higher in the SUP group (4.6%) than in the N group (0.8%; P = 0.016). The prevalence of APA positivity was lowest in the N group. Overall, the clinical characteristics and etiologies of RPL associated with superfertility and subfertility were strikingly similar, with comparable positivity rates after adjusting for maternal age. Further investigation including chromosomal analysis of products of conception is needed to elucidate the clinical impact of differences in fertility on patients with RPL.