Screening tests and scans: week 14–30

During pregnancy you will be offered screening tests to check that you and your baby are healthy.

Screening is your decision – your midwife (or specialist doctor) will give you information and support to help you to decide whether to have screening or not.

At around 18–20 weeks you will also be offered an ‘anatomy’ scan to check for anything unusual about your baby’s body. Find out about:

  • HIV screening
  • diabetes screening
  • screening for Down syndrome and other conditions
  • the anatomy scan
  • other tests offered during pregnancy.

Screening tests can tell you whether you or your baby are more likely to have a medical condition. Some medical conditions can make you and your baby very sick and others can affect how your baby grows and learns. If screening shows that you or your baby may have a condition, you will be offered further tests that will let you know for certain.

HIV screening

You will be offered HIV screening at the same time as you are offered the first pregnancy blood test. HIV screening can also be done at any time during your pregnancy.

HIV is a virus that can make you and your baby sick. Only a very few women have HIV – but for those who do, treatment can help to keep you healthy and well and reduce the chance of HIV passing to your baby during pregnancy, birth or breastfeeding.

HIV screening is free and is recommended by the Ministry of Health. To find out more, go to HIV testing in pregnancy.

Diabetes screening

Diabetes screening is offered twice: as part of the first pregnancy blood test (or any time up until you are 20 weeks pregnant) and again when you are 24–28 weeks pregnant. This screening is to check whether you already have diabetes or if you are at risk of developing diabetes while you are pregnant (gestational diabetes).

Diabetes is when you have too much sugar in your blood, and it can make you sick and affect your baby’s growth. If you do already have diabetes or you develop diabetes in pregnancy, you will be offered information, treatment and support – including help to eat well and stay active.

To find out more, go to Testing for diabetes in pregnancy.

Screening tests for Down syndrome and other genetic conditions

It’s your choice to have screening tests to check whether your baby may have Down syndrome or another rarer genetic condition. These conditions happen at the start of pregnancy and can affect your baby’s growth and development. Screening can provide information about the chance or likelihood of your baby having one of these conditions. Other tests are needed to find out for sure if your baby has a condition.

The screening depends on how many weeks pregnant you are. If you are less than 14 weeks pregnant, this screening is a blood test from you and a scan of your baby. If you are 14–20 weeks pregnant this screening is a blood test only. The blood test is free; you may be charged for the scan.

To find out more, go to Pregnancy screening for Down syndrome and other conditions.

Anatomy scan

The anatomy scan is offered when you are 18–20 weeks pregnant. Parts of your baby’s body will be measured to check that they are growing as expected and to look for any problems.

Having a scan is usually a happy event, but remember that sometimes scans find serious problems, so you should be prepared. Your midwife (or specialist doctor) will give you more information about this scan, including how much it may cost and where you will need to go to have the scan, so that you can decide whether or not to go ahead.

Some people want to find out the sex of their baby before they are born. If you’d like to know, ask the person doing the scan. Be aware that sometimes they may not be able to tell (depending on the position baby is in) and that assessment isn’t 100% accurate. If you don’t want to know, let them know before the scan so that they don’t say anything by mistake.

Other tests

You will also be offered other tests to check that you and your baby are healthy and well. These include regularly checking your blood pressure, urine (wee/mimi) and weight, the size of your baby ‘bump’ and your baby’s heartbeat. These tests are to check that your baby is growing as expected and you are not showing signs of any problems.

Related websites

Screening tests – National Women’s Health (Auckland District Health Board)
Information about screening tests offered during pregnancy.

18–20 week screening pregnancy ultrasound – Inside Radiology (Royal Australian and New Zealand College of Radiologists)
Information on the anatomy scan at 18–20 weeks.

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