An ultrasound usually does not detect pregnancy until about 40 days into the pregnancy. There is no way to see the gestational sac on the ultrasound in the early stages of pregnancy, and it takes about 40 days of pregnancy for the sac to enter the uterine cavity and be visible on the ultrasound. Ultrasound during early pregnancy is mainly used to rule out the possibility of ectopic pregnancy and to observe whether the gestational sac is developing normally. If you want to determine whether you are pregnant as early as possible, you can draw blood to check the chorionic gonadotropin in your blood, or you can use early pregnancy test paper to check. If you are sure you are pregnant, the pregnant mom must pay attention to rest, strengthen the diet and nutrition, how to promote the development of the baby. Do not contact places with strong radiation after pregnancy, and do not take drugs indiscriminately, which can easily cause fetal malformation. It is best to have regular maternity checkups during pregnancy, and regular maternity checkups can understand the development of the baby. If you find abnormal development of the fetus, it is best to take timely measures. If menstruation is delayed for more than a week, it is recommended to use early pregnancy test paper to check, or go to the hospital to take blood tests, in order to confirm whether you are pregnant as soon as possible.