The general pregnancy cycle of 4 weeks is one month, totaling about 280 days (40 weeks). Pregnancy is calculated from the first day of the last menstrual period, because everyone’s menstrual cycle is different, can be checked by a professional doctor according to the early pregnancy ultrasound suggests that the size of the gestational sac and buds, or the length of the head and buttocks to check the week of pregnancy, but also to estimate the expected date of delivery, the month should be subtracted from 3 or add 9, the number of days should be added to 7. The general pregnancy cycle of pregnancy according to the 4-week period is a month, a total of about 40 weeks. From the early pregnancy ultrasound clear intrauterine pregnancy, but also follow the medical advice at 11-13 ⁺ ⁶ weeks of gestation for NT (fetal nuchal translucency) measurement, 15-20 weeks of gestation for Down’s syndrome, 20-24 weeks of gestation for fetal structural anomalies ultrasound screening and other malformations detection test. Standardized OB tests can detect pregnancy risks early and manage them in time to ensure the safety of mother and baby.