How often is pregnancy best checked?

The first pregnancy test is mainly to /confirm/i, at the same time should be clear whether it is intrauterine pregnancy, if the pregnancy days are few, B ultrasound can not see the gestational sac, need to check again after 5-7 days. After clear intrauterine pregnancy, pregnancy before 28 weeks, check once a month. 28-36 weeks should check once a fortnight, 37 weeks before delivery should check once a week.