How to Work Out Your Due Date

The due date is an estimate of when a baby is expected to be born, and it is calculated based on the first day of a woman’s last menstrual period (LMP).

Here are the steps to work out your due date:

  1. Determine the first day of your last menstrual period. This is the first day of the bleeding, not spotting or discharge. If you have irregular periods, it may be difficult to determine your exact LMP.
  2. Count forward 280 days (or 40 weeks) from the first day of your last menstrual period. This is the estimated due date. It is important to remember that this is just an estimate, and only around 5% of babies are actually born on their due date.
  3. You can also use online due date calculators, which will calculate your due date based on the first day of your last menstrual period. These calculators can be found on various pregnancy and parenting websites.



It’s important to note that your healthcare provider will likely perform an ultrasound during the first trimester to confirm your due date and ensure that your pregnancy is progressing as expected. They may adjust your due date based on the measurements taken during the ultrasound.

How Many Babies are Born on Their Due Date?

It’s important to keep in mind that the due date is just an estimate, and only about 5% of babies are born on their due date. Most babies are born within two weeks before or after the due

Additionally, the due date is an estimate based on the assumption that a woman’s menstrual cycle is 28 days long and that she ovulates on day 14. However, many women have cycles that are shorter or longer than 28 days, and some women ovulate earlier or later than day 14. This means that the estimated due date may not be accurate for every woman.

First Baby Scan Ultrasound

As mentioned earlier, an ultrasound performed during the first trimester can provide a more accurate due date calculation. The ultrasound measures the size of the fetus and compares it to an established growth chart to estimate the gestational age. This information can be used to adjust the due date, if necessary. The NHS provide an early pregnancy scan around 11 to 14 weeks.

It’s important to remember that the due date is an important milestone in pregnancy, but it is not the only indicator of a healthy pregnancy. Your healthcare provider will monitor your pregnancy to ensure that your baby is growing and developing properly, and will make recommendations for any necessary tests or treatments. It’s important to attend all scheduled prenatal appointments to ensure the best outcome for you and your baby.

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