The causes of estradiol decline in early pregnancy usually include poor ovarian function, endocrine disorders or bad lifestyle habits of pregnant women, which require prompt medical treatment once detected. 1. Estradiol is a kind of estrogen, which is usually secreted by the ovaries. When the ovaries of women suffer from reduced ovarian function or premature aging, the level of estradiol will naturally decrease. 2. Estradiol is usually regulated by the hypothalamus-pituitary-ovary axis, and when the function of this axis is abnormal, it will lead to endocrine disorders, which will result in the phenomenon of estrogen decline. 3. Malnutrition, irregular diet, excessive weight loss, physical weakness and other bad habits can also lead to a decrease in estradiol in early pregnancy, once found, you need to go to the hospital in time for examination.