This observational study aims to establish a national cohort of patients with hydatidiform mole (molar pregnancy) to investigate its malignant transformation rate and malignant transformation mechanisms, with the goal of developing and promoting precision diagnosis and treatment models across China.

Inclusion Criteria:

1. Clinically or pathologically diagnosed as hydatidiform mole.
2. Availability of complete medical records, including clinical and pathological data.
3. No evidence of myometrial invasion or metastasis.
4. Serum hCG levels normalized after uterine evacuation with at least 6 months of follow-up, OR diagnosed with postmolar gestational trophoblastic neoplasia (pGTN) during follow-up.
5. No history of psychiatric disorders, serious infectious diseases, or immune system diseases (such as systemic lupus erythematosus, myasthenia gravis, HIV infection, etc.).
6. Willing to participate in this study and sign the relevant informed consent form.

Exclusion Criteria:

1. Missing clinical data.
2. Loss to follow-up: Do not return to participating hospital for follow-up visits after uterine evacuation, or could not be contacted for subsequent monitoring of hCG changes.
3. Concomitant malignancies or autoimmune deficiency disorders (e.g., systemic lupus erythematosus, myasthenia gravis, HIV infection, etc.).
4. As determined by the investigator, the presence of medical, psychological, social, occupational, or other conditions that would violate the study protocol or impair the subject's ability to provide informed consent.

This study will enrol women with a confirmed hydatidiform mole who have undergone uterine evacuation. Candidates must possess complete clinical and pathological records and show no myometrial invasion or distant metastasis at baseline. We will exclude those with concurrent malignancy, severe autoimmune or infectious disease, or significant psychiatric illness. Longitudinal follow-up will track malignant transformation (post-molar gestational trophoblastic neoplasia per FIGO criteria), reproductive outcomes, and health-related quality of life. By establishing a large, nationwide, multicentre cohort, we aim to clarify the epidemiology, pinpoint risk factors for malignant progression, and evaluate long-term reproductive and psychosocial outcomes in this population.