If there is still bleeding after one month of taking birth control pills, it may be caused by improper use of medication, embryo abnormality, or systemic diseases of the pregnant woman. 1. Improper use of medication: If the medication is not used in strict accordance with the doctor’s instructions, it will affect the effect of birth control, so there is still bleeding after one month of medication. 2. Abnormal embryo: If the embryo has chromosomal abnormalities, including abnormal chromosome number and abnormal structure, it will lead to abnormal development, at this time, even with the use of medication to protect the fetus, the embryo can not develop normally, and ultimately, it will be eliminated naturally, and spontaneous abortion occurs. 3. Pregnant women have systemic diseases: If pregnant women have some systemic diseases, such as diabetes, chronic inflammation, severe anemia and chronic wasting disease, pregnancy is prone to spontaneous abortion, then even if the use of birth control drugs may not be able to keep.