In 30 days of pregnancy, that is, 30 days after menopause, there is usually no abnormality, it is not recommended to do ultrasound examination. In 30 days of pregnancy, the fertilized egg may still be moving in the fallopian tube, or has just reached the uterine cavity to settle down, and the gestational sac in the uterine cavity is very small, so that through ultrasound, it is not possible to clearly observe the gestational sac in the uterine cavity, and ultrasound examination would not have any significance. The embryo can be predicted by checking the chorionic gonadotropin level in the blood. Ultrasound can only be done on the 40th day of pregnancy to be able to clearly observe the size of the gestational sac in the uterine cavity and whether or not there are any fetal buds. Ultrasound is also needed to assist in the diagnosis of lower abdominal pain in the 30th day of pregnancy when there is a suspicion of ectopic pregnancy or rupture of the corpus luteum, or torsion or rupture of an ovarian cyst.