How to use
1. Take the first day of your LMP (last menstrual period). That's the date that your last period started
2. Moving the middle disc, line up the purple LMP arrow with your own LMP date.
(All dates are clearly marked on the bottom disc.)
3. You can now read off your EDD (expected date of delivery) at the point marked "LMP EDD".
This is your due date according to 'your dates'.
4. If you have a dating scan, you'll be told how many 'weeks' you are by scan.
And if your scan agrees with 'Your Dates', then it's quite simple.
But if your 'Scan Date' is different to 'Your Dates', then it can be very confusing.
6. On an OBDISK the top disc is the one that's turned according to the scan result.
It's easy to read off both sets of dates on your OBDISK at the same time, as the top two discs are transparent.
Basically, 'Your Dates' are shown in purple, and the 'Scan Dates' are in red.
7. Throughout your pregnancy you can see how many weeks you are by dates and by scan, at the same time.
Abbreviation reminder
LMP: Last Menstrual Period
EDD: Estimated Due Date
SCAN: Due date as calculated by the ultrasound scan.