Ultrasound examinations can usually be performed at 5-7 weeks of pregnancy. If the periods are regular, most women can see the gestational sac at 5 weeks of pregnancy and can determine whether the pregnancy is intrauterine or ectopic. If menstruation is irregular and delayed, indicating that ovulation is also delayed, the gestational sac may not be visible until 6 weeks of pregnancy. The germ is usually visible at 7 weeks of pregnancy and the primordial heart tube is pulsating when the germ diameter reaches 2 mm and above. Usually, if you find that your period is delayed by 1 week, you can use an early pregnancy test or a blood HCG test to determine if you are pregnant. Once pregnancy is confirmed, an ultrasound can be done in due course to determine the exact pregnancy status and then treated accordingly. If you already see the fetal heartbeat and germ at 7 weeks of pregnancy, you can wait for NT ultrasound during the period of 11 weeks to 13 weeks + 6 days, after which you will have regular maternity checkups and your doctor will arrange subsequent ultrasound examinations according to the week of pregnancy.