The fetal germ 0.5cm is usually about 49 days of pregnancy, the germ length can be used to calculate the pregnancy week, the germ length (cm) + 6.5 results in the integer part is the pregnancy week, the pregnancy week multiplied by 7 can get the specific number of days, this method is only applicable to 12 weeks before, after that you can estimate the pregnancy week through the value of the biparietal diameter and other values. Some women’s pregnancy days calculated by this formula and their actual days of menopause do not match, commonly in the following two cases: 1, irregular menstruation: some women have irregular menstruation, ovulation time may be early or postponed, the corresponding fertilized egg implantation time will also be early or postponed, so that the number of days of pregnancy does not match the number of days of menopause. In general, women with irregular menstruation can check the pregnancy week by the size of the gestational bud or the gestational sac; 2. Embryonic dysplasia: some embryos are not of good quality, resulting in slow development of the embryo and slow growth of the gestational bud, and the calculated number of days of pregnancy and the number of days of menopause will not match. It should be noted that early pregnancy is an important period for fetal formation, which is easily stimulated by certain physical and chemical factors, resulting in miscarriage and fetal abortion, so it should be taken seriously. If there is bleeding and abdominal pain, consult a doctor promptly. If you need to take medicine, you must consult in advance whether it is available. During early pregnancy, because the embryo is small, it does not need much nutrition, so it is necessary to control the weight gain, and during the three months of early pregnancy, the weight gain should not exceed 2 kg.