The purpose of the study is to understand the effect of nicotinamide mononucleotide (NMN) on patients with diminished ovarian reserve and the outcomes of IVF/ICSI-ET.

Inclusion Criteria:

1. Individuals who are 20 to 40 years old.

2. At least two of the following three conditions should be met:

   1. The concentrations of anti-Mullerian hormone < 1.1 ng/ml,
   2. the values of antral follicle count was less than 7
   3. serum concentrations of day-3 follicle-stimulating hormone (FSH)： 10 IU/L ≤ FSH<20 IU/L

3. Individuals who can insist on continuous monitoring in the outpatient clinic.

4. Individuals who are not participating in other research projects currently or 3 months before the intervention.

Exclusion Criteria:

1. Individuals who are during pregnant, lactation or menopause.

2. Individuals who had non-46-XX karyotype, or attributed to known genetic etiology.

   Individuals who had pelvic surgery.

3. Cancer patients or receiving chemo/radiotherapy treatment within the past 5 years.

4. Individuals who need regular medication to treat chronic diseases such as diabetes, hypertension, gout, hyperuricemia, etc.

5. Individuals who currently receiving weight-loss drugs or surgery or within the past 2 months.

6. Use of medications or traditional Chinese medicine that affect hormone levels, appetite, carbohydrate absorption, and metabolism within the past 3 months.

7. Individuals who take niacin, nicotinamide, or other vitamin B3-related supplementation, or other supplementation such as coenzyme Q10, vitamin E currently or within the past 3 months.

8. Use of antibiotics, probiotics, or prebiotics that affect the flora within the past 3 months.

9. Individuals with severe liver diseases or kidney disease that are ineligible to participate in the study.

10. A medical history of severe cardiovascular and cerebrovascular diseases.

11. Individuals who currently suffer from severe gastrointestinal diseases or undergo gastrointestinal resection that may affect nutrient absorption.

12. Individuals who drink more than 15g of alcohol per day or have a smoking habit.

13. Individuals who need drug treatment for any mental illness such as epilepsy and depression.

14. Individuals who suffer from infectious diseases such as hepatitis B, active tuberculosis, AIDS, etc.

15. Unable or unwilling to follow the study protocol.

Individuals who are during pregnant, lactation or menopause. Individuals who had non-46-XX karyotype, or attributed to known genetic etiology.

Individuals who had pelvic surgery. Cancer patients or receiving chemo/radiotherapy treatment within the past 5 years.

Individuals who need regular medication to treat chronic diseases such as diabetes, hypertension, gout, hyperuricemia, etc.

Individuals who currently receiving weight-loss drugs or surgery or within the past 2 months.

Use of medications or traditional Chinese medicine that affect hormone levels, appetite, carbohydrate absorption, and metabolism within the past 3 months.

Individuals who take niacin, nicotinamide, or other vitamin B3-related supplementation, or other supplementation such as coenzyme Q10, vitamin E currently or within the past 3 months.

Use of antibiotics, probiotics, or prebiotics that affect the flora within the past 3 months.

Individuals with severe liver diseases or kidney disease that are ineligible to participate in the study.

A medical history of severe cardiovascular and cerebrovascular diseases. Individuals who currently suffer from severe gastrointestinal diseases or undergo gastrointestinal resection that may affect nutrient absorption.

Individuals who drink more than 15g of alcohol per day or have a smoking habit. Individuals who need drug treatment for any mental illness such as epilepsy and depression.

Individuals who suffer from infectious diseases such as hepatitis B, active tuberculosis, AIDS, etc.

Unable or unwilling to follow the study protocol.

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Patients' information is requested to be confidential.