A human chorionic gonadotropin test for pregnancy and an ultrasound showing no pregnancy may be biochemical, or the pregnancy may be so early that the ultrasound did not pick up the gestational sac. Soon after the fertilized egg is laid, the human chorionic gonadotropin in the blood will rise, and this is when a blood test can detect pregnancy. However, it will take some time before the gestational sac appears on ultrasound. So if the pregnancy is still short, it is normal for a pregnant woman to have a blood test for pregnancy but not see the gestational sac on ultrasound for the time being, and to be rechecked a week later. If the woman check human chorionic gonadotropin is pregnant, but the value of the test is obviously lower than that of a normal pregnancy, or the rise is slower, and at the same time the ultrasound can not see the gestational sac, then the pregnant woman may be biochemical pregnancy, ectopic pregnancy, preeclampsia, and other conditions, which need to be under the guidance of the doctor to comprehensively determine.