Pre-eclampsia refers to those who show signs of miscarriage but may continue the pregnancy after treatment with birth control. It often occurs in early pregnancy with mild intermittent uterine contractions with or without a small amount of vaginal bleeding called pre-eclampsia, early pre-eclampsia within 12 weeks of pregnancy and late pre-eclampsia from 13 to 27 weeks. The pelvic examination shows that the uterine opening is not open, the fetal membranes are intact, there is no pregnancy discharge, the uterine size is consistent with the gestational week, and there may be a tendency of cervical shortening on ultrasound. If left untreated, it can develop into a refractory miscarriage. Since 62% of miscarriages occur before 12 weeks of gestation, the early appearance of signs of pre-eclampsia must be given sufficient attention and vigilance. One of the most important questions is: Why does preterm miscarriage occur? This is a question that is difficult to answer comprehensively, because up to now, there are still some uncertainties about its causes, but the causes revealed so far are as follows: 1. Chromosomal abnormalities Chromosomal abnormalities are one of the main causes of miscarriage. Chromosomal abnormalities include two major types of chromosomal abnormalities: quantitative abnormalities and structural abnormalities. If one of the couple has a chromosomal abnormality, it can be transmitted to the offspring and can lead to miscarriage or recurrent miscarriage. 2. Maternal factors (1) Endocrine abnormalities such as luteal insufficiency, hypothyroidism, uncontrolled diabetes mellitus, etc. (2) Systemic diseases systemic infections fever can induce uterine contractions causing miscarriage; certain known pathogenic infections such as toxoplasma, cytomegalovirus, rubella virus, herpes simplex, Mycoplasma solium, etc. are associated with miscarriage; ischemic and hypoxic diseases such as heart failure, severe anemia, hypertension, chronic nephritis and severe malnutrition in pregnant women can also lead to miscarriage. (3) Abnormal immune function, such as closed antibody negative. (4) Trauma such as squeezing the abdomen or rapid impact, etc. (5) Bad habits such as smoking, alcohol abuse, excessive coffee consumption, etc. (6) Adverse factors in the environment Such as formaldehyde, benzene, lead and other harmful chemicals. (7) Uterine defects such as congenital uterine malformation, uterine fibroids, etc. (8) Severe malnutrition. (9) Emotional trauma such as excessive excitement, fear, sadness, anger, etc. So, in which cases is birth control possible? Generally speaking, as long as there is no direct evidence that the fetus has chromosomal problems or has been attacked by pathogenic microorganisms or malformations, it should be actively preserved, because at present, most of the pre-eclampsia is caused by endocrine insufficiency, i.e. luteal insufficiency, so it is very reasonable and necessary to use progesterone to actively preserve the fetus. Having said that, one may ask, is there a test that can identify a genetic defect in the fetus at an early stage? The answer is yes, for example, chorionic villus aspiration (suitable before 14 weeks of gestation) and amniocentesis (suitable for 17-23 weeks of gestation) to obtain fetal chorionic cells or amniotic fluid cells for chromosomal examination, but this test can only detect the number and structure of chromosomal abnormalities in the fetus, but can not help with certain genetic diseases, which is its limitation, and this method is invasive, and one of its disadvantages is that it artificially One of the disadvantages of this method is that it artificially increases the probability of miscarriage. The other method is noninvasive genetic testing, which is based on the detection of chromosomal number abnormalities and does not detect structural chromosomal abnormalities or genetic disorders. Therefore, its detection range is less than that of chorionic villus and amniocentesis. Other measures currently used to screen for fetal chromosomal abnormalities include fetal NT and Down’s syndrome screening. The best time to perform this test is between 12 and 14 weeks of gestation. Although this test has some diagnostic value in suggesting fetal chromosomal abnormalities, it is not absolute. Down’s syndrome screening is suitable for singleton pregnant women at 16-20 weeks of gestation and causes a high rate of false positives, so it needs to be combined with fetal NT tests and other tests to determine the risk of fetal chromosomal abnormalities. In general, determining whether a fetus has a genetic defect should follow a non-invasive and then invasive approach, as the latter can artificially increase the probability of miscarriage. If a fetus is determined to have a chromosomal abnormality or an ultrasound suggests a severe structural abnormality, the pregnancy should be terminated as soon as possible at this time. If direct amniocentesis is proposed due to advanced age or other high-risk factors, Down’s syndrome screening is not necessary at this time, but fetal NT screening is still necessary because ultrasound can also rule out fetal structural abnormalities at an early stage.