Menopause 42 days, b ultrasound did not see gestational sac, how to do

Female menopause 42 days later to the hospital to do B ultrasound examination, found that there is no pregnancy sac in the uterus, at this time you can take blood to check the HCG in the body, if HCG has doubled the phenomenon, may be pregnant for a short time, resulting in pregnancy sac has not yet appeared, you can go to the hospital for a period of time to review.