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6. Calculating The Due Date Of Birth

Introduction

1. The Feminine Cycle

2. The Man's Contribution

3. The Fertilisation

4. How A Girl Or Boy Is Created

5. Marking the Ovulation Time

6. Calculating The Due Date Of Birth

Annex.  Female Anatomy

One of the first questions a man and woman ask each other when they know that they have a baby on the way is "when will it be due?".  Well, to be honest, that's up to the baby!  However there are a few simple calculations that can be used to give a good idea of when it should arrive. 

The calculation of the due birth date is by no means an exact science. About 96% of babies DO NOT arrive on the calculated due date, no matter which method is used in the calculation.  To access directly to the different calculators that we have available, Click Here (they all require a Java enabled browser).

The 'Count-Back' method: 

The simplest method of estimating the birth date is to follow a basic mathematical process....

You take the date of the first day of the last menstrual period as the base point (in this example we will use April 1st 2006).

• From this base point, add 7 days... (This gives you April 8th).

• Then subtract 3 Months... (This gives you January 8th).

• If your start date is after March, add one to the year portion of the date.

• This gives a date of "January 8th 2007".

Go to the 'Count-Back' calculator  

The '40-Week' method:

This calculation is again fairly straightforward.  The date of the start of the last menstruation cycle is again used as a base point.  The next step is to simply add 40 weeks from this point.  The problem with this method is that it does not take into account women that have a longer or shorter menstruation cycle.  In these cases, the ovulation point can be different to the usual 28 day cycle.

Go to the '40-Week' calculator

The '266-Day' method (with personalised schedule):

This method tries to take into account the varying menstrual cycles (which is normal between different women).  This method is used by many modern medical practitioners.  An estimation is made of the conception date according to whether it is longer or shorter that 28 days, then a count of 266 days is projected forward from that point.  266 days is the average gestation period for humans from conception to birth.  Note: This gives a date that has a tolerance of plus or minus 3 days.

Go to the '266-Day' calculator

Please note:  All of these calculation methods must be amended after the usual 6 or 10 week scan.  At this time your practitioner can give you more accurate information based on the size of the embryo that has grown up to this point.  This is also the first time that you will have a first inkling as to the status of the young embryo that will become your child.

See the Due Date Calculations Page

Introduction

1. The Feminine Cycle

2. The Man's Contribution

3. The Fertilisation

4. How A Girl Or Boy Is Created

5. Marking the Ovulation Time

6. Calculating The Due Date Of Birth

Annex.  Female Anatomy

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All information provided on this web site is for the purpose of education, information & discussion only and is not a replacement or substitute for consultations with your medical practitioner.  If you have ANY concerns about your health, please see your doctor immediately and do not rely solely on information found here or anywhere else on the internet.