Pregnancy Due Date Calculator

One of the first things a doctor plans after telling a woman she is pregnant is to assess the due date. A normal pregnancy lasts for around 280 days or 40 weeks. Parents spend these 9 months planning for everything that is to be done to welcome the child on the due date. Here, a Pregnancy Due Date Calculator can prove helpful. Read ahead for an overview of this tool.

The Due Date or Estimated Date of Delivery (EDD) is the provisional date on which a pregnant woman is expected to spontaneously progress into labour and give birth. (The word spontaneously is used here to denote that the progression happened naturally on its own and without any medical intervention.) 

The calculation for your EDD starts with knowing your LMP (Last Menstrual Period). The LMP is the date of the first day of the last period cycle you had prior to conceiving. The most commonly used methods of EDD calculation are dependent on knowing your LMP date. This method is only used for women who have their periods in a regular monthly pattern. It cannot be reliably used in those whose periods are irregular.

The Pregnancy Due Date Calculator is for women with period cycles that last for 28 days, which is the average duration of a cycle. It takes into consideration the starting date of your last menstrual period and the average length of your menstrual cycles. Such a calculator can be found online on reliable healthcare websites such as NHS (UK). You simply have to input the data points mentioned above and it will tell you the EDD. 

It works under the assumption that in a 28 day regular menstrual cycle, ovulation occurs on the 14th day from the start of the period. Ovulation is the process where the egg is released from the ovary into the uterus where it can be fertilised by a sperm cell to form an embryo; colloquially known as conception.

It is important to note that this date is an estimate. Most deliveries happen within 2 weeks on either side of the Estimated Delivery Date, with all that duration within term. In fact, only about 4% of deliveries take place exactly on the EDD!

The estimation of EDD by this formula should always be supplemented and confirmed with the help of an Ultrasound Scan. This is also the method of choice for determining the EDD in those mothers who do not have regular period cycles, or those who cannot reliably recollect their LMP accurately. 

Once you confirm your pregnancy by a urine pregnancy test either at home or at a hospital, you must consult your doctor for an ultrasound scan as soon as possible. This scan, also sometimes called a Dating scan, is done in the first trimester (within 14 weeks) and is the most accurate method to determine how long you have been pregnant as well as the most reliable EDD. 

If the EDD determined by Ultrasound done before 14 weeks of pregnancy varies from the EDD that is calculated from your LMP by more than 7 days, then the EDD should be changed to match the one determined by the scan. 

If you have conceived with the help of techniques like IVF, etc., (Assisted Reproductive Techniques), the age of the embryo and the date of the embryo transfer (the process by which it is implanted in the womb) is taken into account for calculating the EDD and the duration of the pregnancy. 

Determining an accurate EDD during your first pregnancy consultation is extremely important. It is vital information for you to know so that you can plan and be prepared. In clinical practice, knowing your LMP, EDD, and gestational age (how far along your pregnancy is) is critical for planning the following. 

Knowing your gestational age and EDD helps your doctor plan your pregnancy in such a manner as to have the ability to diagnose any problems with you or the foetus at the earliest possible juncture. 

Accurate estimation of your EDD and gestational age has a big impact on the course of your pregnancy. If you suspect you are pregnant, make sure to visit your doctor as soon as possible so that you may have a scan done without delay.

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.