Your first trimester scan

The first 12 weeks of pregnancy is called the 'first trimester'.

We offer all pregnant women a scan towards the end of the first trimester. This is usually at around 11 to 14 weeks of pregnancy.

It is important that you have read all the relevant patient information before your appointment.

At the scan we will:

  • check your baby’s heartbeat
  • measure your baby's length to calculate how far through the pregnancy you are and your expected due date
  • look to see how many babies you are having.

The scan is also part of screening for three chromosomal conditions (sometimes also called genetic conditions). These are Down’s syndrome, Edwards’ syndrome and Patau’s syndrome.

Screening tests in your pregnancy

You can choose to have screening for all three chromosomal conditions, only some of the conditions, or no screening at all.

For example, you can opt to have screening for Down’s syndrome only, or Edward’s and Patau’s combined. You can also opt to have screening for all three of the chromosomal conditions.

It is important to note that screening tests can only calculate your chance of having a baby with a chromosomal condition. They will not tell you that your baby has the condition.

Combined Test

In line with National Screening recommendations, all women are offered the Combined Test in the first instance. This screens for Down’s, Edward’s and Patau’s syndromes. 

The combined test involves two tests.

  1. Using the ultrasound scanner, we measure your baby's 'nuchal translucency'. This is a collection of fluid at the back of the baby’s neck.
  2. We take a sample of the mother's blood to measure two hormone markers.

The results of these two tests, combined with the age of the mother, is used to calculate the chance that your baby is affected with the chromosomal conditions screened for.

Quadruple Test

If, at your first trimester scan, your baby is measuring more than 14 weeks gestation, we will offer you the Quadruple Test, instead of the Combined Test.

The Quadruple test can only be performed up to 20 weeks gestation.

It involves the mother having a blood test to measure four hormone levels. The results of these, and the mother's age, is used to calculate the chance of your baby being affected with Down’s syndrome.

The Quadruple test does not screen for Edwards’ and Patau’s syndrome.

We will send you the screening results by letter within two weeks of your blood test.

DNA Reflex Test

At Kingston Hospital, we also offer another screening test called the DNA Reflex test. It is also commonly known as 'Non-Invasive Prenatal Testing (NIPT)'.

This is usually only offered to those found to be at high chance of having a baby affected with a chromosomal condition. However, at Kingston, we offer it to all women, in addition to the Combined or Quadruple test.

DNA Reflex involves a second blood test which measures the amount of the baby's DNA in the mother's blood. DNA is what makes up our genetic material. The test looks for higher amounts of the baby's DNA from chromosomes 21, 18 and 13. These are the chromosomes linked to the chromosomal conditions.

Although this test is more sensitive and accurate than the Combined or Quadruple tests, it still cannot tell you that your baby has a condition. It can only calculate the chance of it.

What happens next

Following your ultrasound scan, if you wish to have any screening, the person doing the scan will ask you to have your blood taken. 

At this stage, you can decide if you would like to have the DNA Reflex test or not. 

You will have one or two samples of blood taken. One for the Combined or Quadruple test, and one for the DNA Reflex test if you have opted for it.

All blood samples are sent to an external laboratory for analysis. The laboratory will do the Combined or Quadruple test first. This will calculate the chance that your baby has a chromosomal condition.

  • If there is a high chance (more than 1 in 300 babies affected), the laboratory will proceed with the DNA Reflex test, unless you have opted not to have it.
  • If there is a low chance (fewer than 1 in 300 babies affected) the laboratory will not proceed with the DNA Reflex test.

You will receive one screening result. This will give either a low or high chance of a chromosomal condition. You will receive your screening result within two weeks of your blood samples being taken. 

If the laboratory has proceeded with the DNA Reflex test, they will not give you your Combined or Quadruple test result. This is because the DNA Reflex test is more accurate and overrides the Combined or Quadruple test result.

If you have a high-chance result, a Screening Midwife will contact you directly to discuss your result and next steps. If you have a low-chance result, the results will be posted to you. Please file these in your maternity notes.

Contact information

Antenatal Screening team

Telephone:

020 8934 6440