The difference between 14 days and 28 days of descending regulation lies in the difference in time and the different dosages of medication used. 1. Time difference: (1) 14 days of down-regulation generally refers to the luteal phase of the use of the program, generally in the luteal phase of intramuscular injection of down-regulation drugs, hormone levels and ultrasound examination after 14 days, if up to standard after the start of the use of ovulation-promoting drugs. (2) 28 days of down-regulation is generally in the menstrual period on the start of down-regulation drugs, in the use of drugs 28 days after the examination, if the down-regulation of the standard, you can continue to use ovulation drugs. 2. Dosage of drugs: (1) 14 days of down-regulation is usually the use of 1 to 1.85 mg of down-regulation drugs. (2) 28 days of down-regulation is generally the use of 3.75mg of down-regulation drugs. The above two programs have their own advantages and disadvantages, in the specific use of drugs also need to be based on their own situation, under the guidance of the doctor to choose the appropriate treatment program.