Unless you have kept an accurate calendar of your ovulation dates, you will need a pregnancy calculator to help you determine the time of conception. Pregnancy calendars are a simple and convenient tool that you can use to help you know how long you have been pregnant. Once you have established this, you can go on to work out your date of conception (two weeks after the first day of your last menstrual period) and once you know the date of conception, you can calculate your due date by adding 280 days to your date of conception. Important to note that some tests require you to be a certain number of weeks pregnant to take them. These include:

  • Non invasive prenatal paternity testing- this test uses free fetal DNA in the mother’s blood but should not be taken if less than 12 weeks pregnancy. This is because there may not be enough fetal DNA in the maternal blood to do the paternity test.
  • Baby gender testing: a sample of maternal urine will show fragments of the unborn child’s DNA. However, if the test is taken too early in pregnancy, there again may not be enough fragments in the urine to conclude the test. Pregnancy calculators are recommended.

If you wish to do either of the above tests and you do not know how long you have been pregnant you can use a pregnancy calculator.


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