I am a blood test is pregnant, but B ultrasound can not see the gestational sac, but no bleeding phe

Pregnancy B-ultrasound examination did not see the gestational sac, considering that the patient's pregnancy days are too few, gestational sac development is still small, in the B-ultrasound examination can not accurately distinguish. Also consider that ectopic pregnancy occurred, such a situation will also occur. It is recommended that the patient check again one week later.