Clinically, 4 weeks of pregnancy is 1 month and 11 weeks is 2 months and 3 weeks. Pregnancy is counted from the 1st day of the last menstrual period as gestational week, gestational month and due date, which need to be calculated according to the natural week, 4 gestational weeks is 1 gestational month, not 30 days is 1 gestational month, the due date is 40 weeks of pregnancy, i.e. 280 days. In the early stages of pregnancy, regular prenatal checkups and prenatal screenings are performed to rule out the possibility of fetal malformations. NT test is performed at 11-14 weeks of pregnancy, which is a very important small screening test to diagnose whether the fetus has abnormal karyotype and any other structural malformations and whether it is at risk of prematurity or Down’s syndrome by measuring the thickness of the nuchal translucency. Pregnant women can take oral multivitamins containing folic acid, avoid strenuous activities and forbid sexual intercourse.