Haan na, starting mein calculation kitna confusing hota hai! Actually 9 months means around 40 weeks, but delivery 37 to 42 weeks ke beech kabhi bhi ho sakti hai. So weeks pe hi dhayan do.
I tracked my whole journey on apps, and they show that 9 months roughly translates to 40 weeks from your last menstrual period. Download a good tracker app, it makes understanding the trimesters so much easier!
Basically, 9 calendar months are equal to 40 weeks because each month has slightly more than 4 weeks. Most doctors will calculate your due date at exactly 40 weeks. Don't stress too much about the exact math.
When I was staying at my mom's place, she used to count 9 months, but my scans always showed weeks. Generally, 40 weeks is considered the full 9 months. It's beautiful how the weeks fly by.
Usually, doctors count pregnancy in weeks rather than months, and a full term is about 40 weeks. It is best to follow your gynac's calculations based on your last period date to avoid confusion.