Share |
Welcome Page | Obdisk | MidAid | Abbramat | Online Shop | How to Buy | Contact Us | Site Map
Obdisk Information | Instructions | Purchase Obdisk
The Professional 3-disc Pregnancy Calculator (Obstetric Wheel)

Instructions for expectant parents
(Based on a regular 28-day menstrual cycle)

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 on your Obdisk 3, line up the purple LMP arrow with your own LMP date. (All dates are clearly marked on the bottom disc.)
3. Line up each day carefully as you follow the calendar around, adjusting the discs very slightly, if necessary, to match the days exactly. You can now read off your EDD (Expected Due Date) at the point marked “LMP EDD”. This is your due date according to your last period.
4. If you have a dating scan, you’ll be told how many ‘weeks’ you are by scan. Simply turn the top disc, so that it agrees with your scan dates.
5. It’s easy to read off both sets of dates on your Obdisk 3 at the same time, because the top two discs are transparent.
Basically, your ‘period dates’ are shown in PURPLE, and the ‘scan dates’ are shown in RED.
6. Throughout your pregnancy you can see how many weeks you are, by dates and by scan, AT THE SAME TIME.
Please Note
Your due date may be calculated differently if you don’t have a regular 28-day menstrual cycle.
And if there’s a difference between your ‘period dates’ and your scan dates, you may wonder why. Different hospitals have different policies about how to deal with a discrepancy, but your midwife or doctor will be able to explain this to you.

LMP: ‘Last Menstrual Period’
EDD: ‘Expected Due Date’ or ‘Expected Date of Delivery’

There are many different terms for ‘pregnancy calculator’.
An Obdisk could be called any of the following:

Obstetric calculator, 3-disc Obstetric calculator, Obstetrical calculator, Obstetric wheel, Pregnancy wheel, Gestation/ gestational age calculator, Human gestation period calculator, Fetal gestation calculator, Foetal wheel, EDD wheel, Ob dating wheel, Pregnancy dating calculator, Due date calculator, Pregnancy dating calendar, Pregnancy disc/ disk, Midwifery wheel, Midwife's calculator, Midwives’ disc, Manual date wheel, Rotary pregnancy calculator…
But whatever you choose to call it, an Obdisk is a professional essential.
And it’s perfect for expectant parents too.

Different Obdisk models are now available.

The Obdisk 3 and other Obdisk models are available to buy now from the
Website Shop Or please contact us for further information

  Products for Childbirth, Midwifery & Nursing  
  Obdisk: Professional 3-disc Obstetric Calculator  
 order obdisk3 
midaid bottom panel