There are many reasons for the biochemistry of in vitro embryos after implantation, and the specific reasons can not be accurately determined, and there are common maternal factors, external factors, and embryo factors. Maternal factors: 1. Women who are older may experience a decrease in endometrial tolerance, which in turn leads to a decrease in the pregnancy rate and an increase in the rate of biochemical pregnancies and miscarriages. Abnormal immune function and low hormone levels are also causes of biochemistry after embryo transfer. 2. If the woman herself suffers from basic diseases, such as hyperthyroidism or hypothyroidism, etc., which reduces the ability of embryo implantation and endometrial tolerance, the chances of biochemistry after embryo implantation will also increase. External factors: smoking and second-hand smoke, alcohol consumption, exposure to chemical poisons, severe noise and vibration, abnormal emotional excitement, high temperature environment can lead to placental and fetal damage, resulting in miscarriage. Embryonic factors: Most of the embryos themselves are of poor quality, or accidental factors lead to chromosomal mutations in the fertilized egg, thus resulting in miscarriage. When preparing for pregnancy, you should regulate your own physical condition, ensure adequate nutritional intake, you can first go to the hospital for pregnancy test, to ensure that you are in good health, to be fully prepared for pregnancy.