At pregnancy term measure by weeks, but weeks go from the moment of conception or...

[The anonym]

At pregnancy term measure by weeks, but weeks go from the moment of conception or from last menses? At me the menses was 10 go, I consider or count that 24 I have become pregnant. What term at me now? 1 week or 3 weeks?

[Pasenjuk A.M.]

There are two calculations - obstetric - from first day of last menses; and gestatsionnyj - from day of conception. Obstetric term - 3 weeks, gestatsionnyj - 10 days.