How to find the exact date of pregnancy

Check the precise day of pregnancy, can pass through the last menstruation, B ultrasound examination, especially in the case of menstruation is more regular, the last menstruation is more accurate, some people menstruation irregular, it needs to be verified through B ultrasound. Generally in early pregnancy can pass the gestational sac size, fetal bud length, especially pregnant in about 12 weeks, do nt check, the accuracy of measuring fetal bud length is relatively high, this time can also do Down screening, see if there is abnormal baby, usually in addition to determine the time, but also need to closely monitor the baby's development, in the diet above to protein content is relatively high food-based.