What diseases are targeted by prenatal diagnosis? 1.Diseases with clear diagnostic criteria and accurate and reliable prenatal diagnosis methods; 2.Diseases with serious symptoms resulting in stillbirth, stillbirth or disability; 3.Diseases without effective treatment; 4.Diseases with high genetic risk. Indications for prenatal diagnosis: 1. Pregnant women aged 35 years or above; 2. Pregnant women with positive serum screening in early or mid pregnancy; 3. Pregnant women with one of the spouses being a chromosomal disease patient or having had a pregnancy or child with chromosomal disease; 4. Pregnant women with one of the spouses being a congenital neural tube defect patient or having had a pregnancy or child with this disease; 5. Pregnant women with a history of unexplained spontaneous abortion, malformation, stillbirth or stillbirth; 6. Pregnant women with fetuses at high risk of severe monogenic genetic diseases; 7. Those with abnormal fetal ultrasound findings (including excessive amniotic fluid); 8. Prenatal diagnosis methods: Prenatal diagnosis methods are generally divided into two categories according to the different methods of sampling and examination, namely traumatic methods and non-traumatic methods. The former mainly includes amniocentesis, chorionic villus sampling, umbilical cord blood sampling, fetoscopy and embryo biopsy, etc.; the latter includes ultrasonography, maternal peripheral serum marker determination and fetal cell testing, etc. The latter includes ultrasound, maternal peripheral serum marker measurement and fetal cell testing. At present, prenatal diagnosis is still dominated by invasive methods, with amniocentesis and chorionic villus sampling being the two most commonly used. The following risks are associated with the sampling: 1) transient fetal bradycardia; 2) preterm delivery or intrauterine fetal death in 0.1-0.9% of cases; 3) umbilical cord placental oozing after cord blood sampling; 4) rare intra-amniotic cavity infection after amniotic fluid sampling.