Repeat Samples

There needs to be enough fetal DNA in the maternal blood to be able to provide a result. If there is insufficient fetal DNA in the sample (occurring in 3% of cases), another blood sample from the mother may be required. This will be processed in the laboratory at no extra charge.

What is the process?

​Once you have taken an independent personal decision that you want to have the non-invasive prenatal test performed, you will be asked to sign a consent form and your blood sample can be taken from a vein in your arm.

Who carries out the analysis of the test?

​We will send your blood sample along with your personal information (including name, date of birth, gestational age) to The Doctors Laboratory based in London, UK, which has an arrangement with a company called Ariosa Diagnostics Inc, based in San Jose, CA, USA. Ariosa will perform their non-invasive test called Harmony™ Prenatal Test on the DNA extracted from your blood sample.

  • What is this test
  • Safety of the Test
  • Accuracy
  • Who can have the test?
  • Repeat Samples
  • Do I need to have any other tests?
    • Due date & Gestational age based on period

      Due date & Gestational age based on period

      Due Date Calculator based on Last Menstrual Period (LMP).
      Enter the first day of your Last Menstrual Period and the length of your cycle in order to estimate your Due Date and the gestational age at present.
      Note, all dates given are estimates; We will give you a more accurate indication of your due date when you have your 7-10 week ultrasound scan.

      Enter first day of last menstrual period:

      Length of menstrual period cycle:

    • Gestational Age based on Due Date

      Gestational Age based on Due Date

      Gestational Age based on the Due Date
      If you know your due date, you can calculate how many weeks of pregnancy you have completed so far.

      Enter your due date:

    • Fertility calculator

      Fertility calculator

      Enter the date of your last menstrual period and the length of your cycle to show the period at which you are most fertile.

      Date of your first day of your last menstrual period:

      Ferility Window: