What are routine pregnancy scans?

In the UK, all women and pregnant people are offered a minimum of two routine scans. One is called the dating scan - but it’s colloquially known as the 12 week scan. The second scan is the anomaly (or anatomy) scan - also known as the 20 week scan. Some NHS Trusts now also routinely offer a growth scan at around 36 weeks, but this is not a national standard in the UK.

The 12-week dating scan

What does the 12-week scan involve?

The 12-week scan is offered between 10 and 14 weeks of pregnancy and one of its purposes is to estimate how far along you are in your pregnancy. It’s at this scan that you’re given an ‘estimated due date’, which can differ from the date you had worked out based on the first day of your last period. It’s always worth remembering that only 3-5% of babies are actually born on their estimated due date. The 12-week scan can also identify how many babies are growing - one, two or perhaps even three!

Screening for chromosomal conditions

In addition to dating your pregnancy, the 12-week scan also forms part of a screening test for three chromosomal conditions. If you opt to have this screening test (called the combined screening test) the sonographer will measure the fluid-filled space on the back of your baby’s neck, which is called the nuchal translucency. You’ll also be offered a blood test, usually one the same day as the scan. The results of the ultrasound scan and your blood results will be combined to see if your baby has a high or a low chance of having one of the three chromosomal conditions: Down’s syndrome (T21), Edwards’ syndrome (T18) and Patau’s syndrome (T13). If for any reason you have a scan after 14 weeks, you’ll be offered an alternative screening test called the Quadruple test. This is a blood test offered between 14+2 and 20+0 weeks of pregnancy that screens for Down’s syndrome only, and you’ll be offered ultrasound screening for signs of Edwards’ and Patau’s syndrome at the 20 week scan, if you choose to have that.

Screening tests are not diagnostic - what this means is that you could be told you have a higher chance of having a baby with one of these chromosomal conditions and you would then be offered diagnostic testing to confirm this - this could either be via an amniocentesis or chorionic villus sampling (CVS).

You can choose if you want to have the screening at all, if you’d like to screen for all the conditions or if you’d like to choose which conditions you want to be screened for. About 85% of babies with Down’s Syndrome and 80% of babies with Edwards’ or Patau’s Syndromes are identified by combined screening. The Quadruple test can detect around 75% of babies with Down’s syndrome.

Antenatal Results and Choices (ARC) is a charity that provides information about screening tests and results, diagnostic tests and is able to offer support to parents. It’s a useful resource both for deciding about having scans and in the event that a chromosomal condition is suspected or identified.

The 20-week anomaly scan

What is the sonographer looking for?

At the 20 week scan the sonographer is looking at the anatomy of the baby and screening for 11 conditions, including spina bifida and cardiac anomalies. They also assess where the placenta is growing and make sure it’s not covering (placenta praevia) or too near the cervix (low-lying placenta. The scan can also check that for a rare condition where the placenta has attached through the lining of the uterus into the muscle and/or beyond (read more about the Placenta Accreta Spectrum here). Like with all screening tests, the 20 week will not pick up every single condition.

The history of routine pregnancy scans in the UK

Ultrasound scans were developed in the 1950s but didn’t really start to form part of maternity care until the 1970s. In the early 2000s, the NHS developed the Fetal Anomaly Screening Programme (FASP) which included implementing the 12 and 20 week scans as part of standard care for all women across all NHS trusts. Regardless of where you give birth and who you choose to be your care provider in pregnancy, you should be offered these scans in pregnancy.

Potential benefits of pregnancy ultrasound scans

Pregnancy ultrasounds are a non-invasive tool that can identify when there is a problem. For example, if your baby has an anatomical abnormality the scan may highlight this and prompt further review and testing. It can also be beneficial to know where the placenta is lying as this may affect how you plan to give birth - conditions like placenta praevia or placenta accreta are not compatible with vaginal birth and knowing this ahead of time is useful to plan birth and help prevent serious complications. Scans can tell you what position your baby is in, for example head down or breech and this may also influence your plan for birth. They can identify if you’re having more than one baby, which changes the care you’re offered and if you need more specialist input. When the umbilical dopplers are assessed (this relates to the blood flow between the baby and the placenta) they can form part of a wellbeing check for your baby too - particularly where babies are growing smaller than expected.

Potential limitations of pregnancy ultrasound scans

Scans don’t always pick up if your baby does have a condition. They can only tell you at that point in time that your baby is well, having a scan isn’t a guarantee that your baby will be okay. It’s commonly accepted that growth scans have a 15% error margin - meaning the estimated fetal weight that is generated could be as much as 15% more or less than what the baby actually weighs when it’s born. This is important as sometimes women are told they have a large baby and this then has implications for their care. Rachel Reed wrote a brilliant article highlighting the impact a ‘big baby’ label has on women and birthing people’s birth outcomes - but not because of the actual size of the baby, but because of healthcare provider fear when it comes to suspected big babies.

Your right to choose: accepting or declining scans

Can I decline a scan or consent to only part of a scan?

You’re not obliged to have any scans at all in your pregnancy - it’s always your choice. As a society we have accepted routine scans as part of pregnancy care, so it’ill likely be assumed that you will have a scan. However, your midwife should always discuss the pros and cons of scans with you so that you can make an informed choice. You may wish to have a scan at one point in your pregnancy but not at another. You may want to have all the scans that are offered to you. It’s also possible to consent to only part of the scan, for example at the 12 week scan you may choose to not have the nuchal measurement or at a later scan you may wish to not have your baby’s weight estimated. In the event that you don’t want to have all parts of the scan, you need to make this clear to the sonographer before the scan starts.

What are the alternatives to scanning for chromosomal conditions?

Non-invasive prenatal testing (NIPT aka The Harmony Test) is an alternative method of screening for chromosomal abnormalities. It involves a single blood test. Currently it’s not offered as standard on the NHS in England, but is offered to women who receive a higher chance result from the combined or quadruple test. Several professional bodies, including the Royal College of Obstetricians and Gynaecologists (RCOG), have recommended that the NIPT be rolled out in the NHS as standard for all women and birthing people given its higher level of accuracy when compared to the standard options available.

You can pay to have the NIPT privately - which is something we offer. The NIPT detects the chromosomal conditions 99% of the time, which is significantly more sensitive than the combined screening test or the quadruple test.

Choosing independent midwifery care in Folkestone and Kent

What is independent midwifery care?

Independent, or private, midwifery care is care by midwives who do not work for the NHS. Instead independent midwives work outside and alongside the NHS, but have the same referral rights as an NHS midwife. Most independent midwifery care will happen in the comfort of your own home, but we also can attend any appointments or scans you may have during your pregnancy and we can support you in a non-clinical capacity if you give birth in hospital. Care can begin the moment you find out you’re pregnant, throughout your birth and then for 4 weeks after your baby is born. Independent midwifery offers a safe, personalised and compassionate alternative to NHS midwifery care.

How do Juno Midwives support scan decisions during your pregnancy?

We discuss the routinely offered scans with all our clients and have plenty of time to go through the pros and cons. The choice is always yours to make and if you choose to have scans, we’ll support you and if you choose not to have scans, we’ll support you too! If you have agreed to have your belly measured (symphysis fundal height or SFH) during pregnancy as a means of assessing your baby’s growth, there may be occasions when a measurement is smaller or bigger than anticipated. This would prompt a discussion about growth scans, the pros and cons of these and potentially a recommendation for a scan. Again, we’ll support you whatever you choose and we’re able to make the scan referral for you. Scans are also offered if you report reduced fetal movements (depending on your gestation at the time) - and if this situation arises this is something we discuss with you.

Can I have a homebirth in Kent with private midwives and still access NHS scans?

Yes - choosing independent or private midwifery care does not exclude you from accessing any NHS care in your pregnancy. You are still entitled to blood tests, ultrasound scans, care during your pregnancy, birth and afterwards too. Most of our clients choose to have scans with the NHS, it is however also possible to have scans (including the anatomy scan) privately if you’d prefer. We can signpost you to a fetal medicine specialist in Kent who offers ultrasound scans in pregnancy.