About tests in pregnancy
During your pregnancy, your midwife or doctor might recommend that you have some tests to check your health and your baby’s health and development. These could be ultrasound, blood, urine and swab tests.
The results of these tests help you and your health professional plan your options for pregnancy care and birth.
You have to give your permission for your doctor or midwife to do tests in pregnancy. It’s OK to ask your health professional for more information about tests – what they’re for, why you need them, and what could happen if you do or don’t have them.
In pregnancy, you can also have screening and diagnostic tests for chromosomal abnormalities and other conditions in your baby. Tests for chromosomal abnormalities and other conditions are different from the health and development tests described in this article.
Ultrasound scans in pregnancy
You might be offered an ultrasound scan at 11-13 weeks (usually called the 12-week scan). Health professionals also usually recommend you have an ultrasound scan at 18-20 weeks (usually called the 20-week scan).
The 12-week ultrasound scan:
- shows whether you’re having more than one baby
- can work out the age and due date of your baby
- can screen your baby for Down syndrome and other chromosomal conditions.
Your doctor might also recommend an ultrasound scan if you have bleeding from your vagina or abdominal pain in early pregnancy. These symptoms might be – but aren’t always – a sign of miscarriage early in pregnancy.
The 20-week ultrasound scan:
- checks that your baby is growing normally
- checks the position of your placenta
- looks at your baby’s body parts and can usually pick up any problems like spina bifida, heart defects and limb defects
- might indicate that your baby has a genetic abnormality.
If you’re interested in finding out your baby’s sex, you can ask the ultrasonographer doing the 20-week ultrasound to look. But the ultrasonographer won’t always be able to tell the sex for sure.
You might have extra scans before or after this if you’re having twins or more, if you have a medical condition, or if you’ve had problems in previous pregnancies.
Most ultrasounds show that babies are developing normally, but sometimes ultrasounds can pick up abnormalities. Some fetal abnormalities aren’t serious and won’t need much, if any, treatment. But other abnormalities can be a sign of serious disability. It’s worth thinking about how you might feel if your ultrasounds show abnormalities.
Blood tests in pregnancy
Your midwife or doctor will want to do a blood test in early pregnancy to find out your blood type and check for some infections and other health concerns.
These include your rubella immunity, and whether you have anaemia, HIV, hepatitis B or syphilis. Depending on your results, your health professional will let you know about the best treatment for you in pregnancy or straight after the birth.
Rh type blood test
It’s important to test your blood to find out your blood type and Rh type.
If you’re Rh-negative, and your baby turns out to be Rh-positive, this can cause serious health problems for your baby. But no-one knows what your baby’s blood type is until after birth. So if you’re Rh-negative, you’ll be offered a special injection called Anti-D at your 26-28 week antenatal appointment and your 34-36 week appointment.
You’ll also be offered Anti-D if you have bleeding during pregnancy. This reduces the risks of health problems.
After your baby is born, blood is collected from your baby’s umbilical cord and the Rh type is checked. You’ll have another Anti-D injection if your baby is Rh-positive.
Gestational diabetes blood test
The blood test for gestational diabetes is usually done at 24-28 weeks of pregnancy. If you’ve had gestational diabetes in a previous pregnancy or you’re at high risk of getting this condition, your health professional will probably suggest you have the test earlier.
The test usually involves a glucose tolerance test (GTT), where you have to fast (not eat or drink) overnight. Your blood is tested, then you drink 75 gm of glucose in a sugary drink. You have your blood tested twice more – after one hour and after two hours.
If you have high blood sugar levels on a glucose tolerance test, you’ll be diagnosed with gestational diabetes.
If you have gestational diabetes, it means you have a high-risk pregnancy and need special care and management. If the diabetes isn’t managed carefully, it can cause serious problems for you and your baby. You might be referred to a high-risk pregnancy clinic and diabetes educator for help with managing your diabetes.
Urine tests in pregnancy
Some urine infections don’t have symptoms, so a urine test is recommended at your first antenatal appointment to check whether you have an infection.
You might be offered a urine test at other times during pregnancy as well.
The test usually involves you urinating into a small jar. Sometimes you can do this at home and take the jar with your urine sample to your doctor’s or midwife’s consulting rooms. Or you might just do it while you’re at your appointment with the doctor or midwife. Your health professional will tell you exactly what to do and send the sample for testing.
This test is important because if urine infections aren’t treated, they can cause premature labour or low birth weight in your baby.
Urine tests also look at sugar, blood and protein in your urine. These things can be signs of other medical concerns.
Group B streptococcal (GBS) test
Group B streptococci (GBS) are bacteria that often live in the vagina and anus. They don’t usually hurt you. But if the bacteria pass to your baby during birth, this could cause an infection that might make your baby very sick.
There are two ways of reducing the chance of your baby getting a GBS infection. Different hospitals or health care providers will recommend one of these ways. Both ways are effective.
The first way is a screening method called a ‘low vaginal swab’ at about 36-38 weeks. This involves wiping a special stick (called a swab) just inside your anus and vagina. You can do this yourself, but you’ll probably do it in your doctor’s or midwife’s consulting room. Your doctor or midwife sends the stick away to be tested for GBS.
If you have GBS, you’ll be offered intravenous antibiotics during labour to lower the risk of infection to your baby.
The other way is to give intravenous antibiotics to women who have risk factors in labour without doing the swab in pregnancy. The risk factors can be when:
- the baby is premature (less than 37 weeks)
- the woman has had a baby with a GBS infection in the past
- it’s been over 18 hours since the woman’s waters broke
- the woman has a temperature in labour
- GBS is found in a urine test.