{"paper_id":"9f6ef019-a96d-494b-9225-c288f32a72f0","body_text":"A robust endometrial growth pattern is crucial for successful implantation. Ultrasonography often identifies patients with reduced\nendometrial thickness [ 1 ]. Numerous studies have associated low implantation rates with a \"thin\"\nendometrium, which is recognized as a critical factor in implantation failure [ 2 ]. Thin\nendometrium (TE) is defined as an endometrial thickness of ≤7 mm on ultrasonography [ 3 ,\n 4 ]. Enhancing endometrial development in women with TE remains challenging, despite several\ninterventions including low-dose aspirin and estrogen therapy [ 3 ]. Irregularities in endometrial\ngrowth have long been considered a key cause of thin endometrium. An essential component of assisted reproduction is the evaluation of\nthe endometrium, as endometrial thickness is a predictor of success [ 5 ,  6 ].\nWhen the uterine lining is classified as \"thin,\" both patients and clinicians face the difficult decision of whether to continue with\nthe treatment cycle. However, there remains insufficient understanding of the factors contributing to diminished endometrial growth in\nwomen with thin endometrium [ 7 ]. Therefore, it is of interest to evaluate the etiological aspects\nof thin endometrium.\n\nIt was a retrospective study at a tertiary care and IVF centre. After considering the utility of the study and obtaining approval\nfrom the ethical review committee, 61 patients of infertility with thin endometrium from January 2019 to December 20204 were enrolled\nfor the study. Data such as name, age, etc., was recorded. The ultrasonographic definition was a maximal endometrial thickness of no\nmore than 7 mm, as measured by transvaginal ultrasound scans before ovulation or after the administration of human chorionic gonadotropin\n(hCG). The causes of thin endometrium were recorded. The results were compiled and subjected to statistical analysis using the\nMann-Whitney U test. A p-value less than 0.05 were regarded as significant.\n\nThis study included 61 female patients with infertility, where the ultrasonographic measurement defined a thin endometrium as having\na thickness of no more than 7 mm. The causes of thin endometrium were recorded and analyzed. The average age of the participants was\n34.5 years, and the mean BMI was 23.8 kg/m 2 . The mean parity was 1.2, indicating most participants had one previous\npregnancy. The average duration of infertility was 4.5 years, highlighting a prolonged period of infertility among the participants\n(Table 1 - see PDF). The most common cause of thin endometrium was tuberculosis, observed in 18 cases, followed by a history of repeated\ncurettage (12 cases). A significant portion of the cases (21) had no identifiable cause, categorized as unexplained (Table 2 - see PDF).\nAdvancing age was the most commonly associated factor present in 28 cases, followed by parity (14 cases) (Table 3 - see PDF). The\nhormonal profile of the participants showed an average TSH level of 2.8 mIU/L, a Prolactin level of 16.3 ng/mL, an LH level of 6.1\nmIU/mL, and an FSH level of 7.9 mIU/mL. These values indicate a range within normal limits for most participants, though individual\nvariations might contribute to the etiology of thin endometrium (Table 4 - see PDF). The mean uterine artery (UA) resistance index (RI)\nwas 0.92, and the mean radial artery (RA) resistance index (RI) was 0.84 (Table 5 - see PDF).\n\nEndometrial receptivity is fundamental to implantation and pregnancy success in both natural and ART cycles [ 8 ].\nCurrently, there are no standardized criteria to evaluate endometrial receptivity in IVF patients [ 9 ].\nSeveral ultrasonographic parameters-including thickness, echogenicity and pattern-have been assessed for their potential to predict\nimplantation and pregnancy outcomes [ 10 ,  11 ]. Despite\nabundant literature, the predictive reliability of endometrial thickness remains debated, although some studies have noted a positive\nassociation between endometrial thickness and pregnancy rates [ 12 ,  13 ].\nThe present study aimed to explore the etiological factors linked with thin endometrium. Shufaro  et al. \n[ 14 ] reported that 13 of 1,405 IVF patients repeatedly exhibited unresponsive thin endometrium\n(<7 mm), with 10 of them having a history of curettage-comparable to our observation of 19.6% with prior curettage. Similarly, Liu\n et al.  highlighted that intrauterine surgeries such as D & C and adhesion lysis were leading causes of thin\nendometrium [ 15 ]. In our cohort, 29.5% had a history of genital tuberculosis, aligning with\nSharma  et al. 's finding of TB history in 67.8% of women with thin endometrium [ 16 ].\nAdvancing age was the most frequently associated factor in our study (28 cases), followed by parity (14 cases), while uterine fibroids\nand endometriosis were each found in 4 cases. The mean uterine artery resistance index (UA-RI) was 0.92±0.18, and the radial\nartery resistance index (RA-RI) was 0.84±0.12, both of which were elevated. These findings correspond with previous studies\nshowing significantly increased RA-RI in patients with thin endometrium across the menstrual cycle, suggesting the role of vascular\nresistance and hormonal alterations [ 17 ]. Pulsed-wave Doppler studies further support that high\nuterine artery resistance is associated with adverse ART outcomes [ 18 ]. Dain  et al. \nreported no statistically significant difference in CPR or LVBR between groups with endometrial thickness <6 mm and those with\ngreater thickness, but observed more live births with 8.2 mm cut-off [ 19 ]. However, an Endometrial\nthickness < 8.2 mm was linked to lower live birth rates. A thin endometrium may fail to support implantation and fetal growth,\nleading to increased miscarriage and intrauterine death. Notably, patients with <6 mm Endometrial thickness had a higher prevalence\nof Grade A endometrial patterns and fewer Grade C patterns, indicating altered endometrial morphology.\n\nThe most common cause of thin endometrium was tuberculosis, followed by endometrial curettage and chronic endometritis. A large\nnumber of cases were idiopathic.","source_license":"CC0","license_restricted":false}