You need to know not only when the ultrasound will show pregnancy, but also the reasons why it is not confirmed. Sometimes the test indicates that there is a pregnancy, and during an ultrasound examination, the embryo is not detected. For example, if the procedure is carried out too early. With a delay of several days, the test may already show a second strip, however, an embryo may not be noticed on an ultrasound scan - its size is less than one millimeter. Therefore, you do not need to immediately run for an ultrasound. Even if you can't wait, you should wait 2 weeks.
Chorionic gonadotropin can increase due to tumor formations in the liver, as well as with cystic mole during pregnancy - this is a dangerous anomaly, so there is a need for additional research.
The probability of error during ultrasound in the early stages is approximately 1:10. It may be due to poor-quality equipment or insufficient qualifications of a specialist. However, such cases are becoming increasingly rare. As a rule, even at an early date, the doctor can determine the exact date of conception.
It is interesting, of course, to find out after how many days you can see the sex of the child. But in the early stages, no one will report this. Therefore, it will be possible to choose pink or blue with confidence only after 15-18 weeks.