• Baoyi Huang, Danying Lu, Yanxiang Kong, and Lin Ma.
• The Reproductive Medical Center, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong, China.
• Medicine (Baltimore). 2024 Mar 1; 103 (9): e37399e37399.

RationaleThe success of pregnancy depends on various factors, with the endometrial receptivity being a crucial component. Endometrial thickness (EMT) serves as a direct indicator for assessing endometrial receptivity. Previous studies have suggested that a thin endometrium is associated with lower pregnancy rates, especially in patients with an EMT of less than 4 mm. Even in assisted reproductive technology cycles with high success rates, clinical pregnancy cases in patients with such thin endometrium are reported to be very few, let alone in natural conception cycles. Therefore, a thin endometrium poses significant challenges for infertility patients. In this study, patients with an extremely thin endometrium were able to achieve clinical pregnancy and successful live births through natural conception, highlighting the possibility of success even in challenging cases.Patient ConcernsThe patient presented with polycystic ovary syndrome and ovulation disorders. She underwent a natural cycle of letrozole-induced ovulation. On the day of the human chorionic gonadotropin trigger, she had an EMT of 3.8 mm.DiagnosesPolycystic ovary syndrome, ovulation disorders, thin endometrium.InterventionsThe patient received medications including Progynova, Aspirin, and Dydrogesterone.OutcomesThe patient achieved spontaneous conception and subsequently had a live birth.LessonsThis case report underscores the significance of managing a thin endometrium during letrozole-induced ovulation. While EMT is traditionally pivotal for predicting embryo implantation success, our findings indicate that endometrial receptivity extends beyond thickness alone. Factors such as endometrial morphology, type, and blood supply play crucial roles. Successful pregnancies with a 3.8 mm EMT are rare, making this case a beacon of hope for such patients. It highlights that, with appropriate interventions, successful pregnancies remain attainable. For those with a thin endometrium, emphasis should extend beyond thickness, addressing ways to enhance both endometrial blood supply and morphology for improved pregnancy rates.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.

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