The process of sperm-egg union, i.e. the formation of a fertilized egg, takes about 24 hours. The completion of the fertilization process is marked by the complete fusion of the chromosomes of the egg nucleus and the sperm nucleus in 6-7 days afterwards. After the sperm and egg have united to form a fertilized egg, it is not possible to determine whether sperm-egg union has occurred before the fertilized egg has settled in the uterine cavity, but only after the fertilized egg has settled in the uterine cavity, through clinical manifestations and auxiliary examinations. 1. Judgment of sperm-egg union 1. Clinical manifestations Menopause, early pregnancy reaction, frequent urination, breast changes, and vaginal mucosa and cervical-vaginal congestion with purple-blue color. (1) Pregnancy test: soon after the fertilized egg is laid, the HCG level in the blood of the test subject can be measured by radioimmunoassay; (2) Early pregnancy test paper: the test result is positive; (3) Ultrasonography: the gestational sac can be seen. In order to ensure the successful union of sperm and egg, the couple must have the following conditions: 1) the male has normal sexual function and is able to ejaculate normally; 2) the male has enough sperm of normal form and function and a liquid environment suitable for sperm to swim; 3) the female is able to produce normal and mature eggs and the fallopian tubes are open; 4) normal sexual intercourse occurs before and after the female’s ovulation period to ensure that the sperm and egg are intact. 4. Normal sexual intercourse occurs around the time of ovulation to ensure that the sperm and egg have a chance to meet.