National Institutes of Health, National Library of Medicine, , December 2020.
That's because healthcare providers use your last menstrual period to , so technically the first day of your period is also the first day of your pregnancy.
Routine second trimester ultrasounds are usually done in 2D.
They think I should be 5weeks but to me that is mathematcially not possible as I definatly know the date when I could have conceived.
For example, drinking healthy herbal tea abundantly would be helpful.
But that's still a long way away.