1.Disease activity period (1), temporarily unsuitable for pregnancy: heart disease, hepatitis, nephritis, tuberculosis, diabetes, hyperthyroidism, asthma, epilepsy, high fever; tumors (abdominal, pelvic, breast, thyroid) should be operated before pregnancy, so as not to aggravate or difficult to deal with during pregnancy; reproductive tract infections, sexually transmitted diseases, serious urinary tract infections; viral infections <3 months; long-distance business trip fatigue and return <2 weeks; serious of mental trauma (excessive sadness, depression, tension or facing great stress). (2) Diseases that prevent pregnancy for life: dementia of one or both partners, mental illness, severe heart disease, cardiac insufficiency or heart failure. (2) harmful substances (1) being on medication: chronic diseases are taking medication or <3 months after stopping medication; during or after stopping the use of contraceptives (oral, implant) <3 months. (2) Before the exclusion of environmental pollution factors; (3) <3 months after drug use, excessive smoking, alcohol consumption, detachment from toxic substances (pesticides, lead, mercury and cadmium), X-rays; ④ <6 months after radiotherapy. 3.Post-pregnancy Within two years after cesarean section; within six months after natural delivery; those whose menstruation has not returned to normal after abortion, medical abortion, curettage or IUD removal; those who are free of malignant gravida and choriocarcinoma after 2 years of tracking after gravida clearance can be considered for pregnancy. 4, climate abnormalities strange cold and heat, heavy rain and thunder, frequent sunspot activity, flash floods, volcanic eruptions, earthquakes, tsunamis, nuclear radiation.