Tests during pregnancy

Once your pregnancy has been confirmed you’ll be offered a variety of tests and checks to ensure that everything is progressing as it should. These will range from taking a urine sample, through to ultrasound baby scans and if necessary screening for certain conditions.

The basics

On your first booking appointment you’ll be weighed so that the doctor or midwife can determine your body mass index (BMI). This is your weight in kilograms divided by your height in metres squared. This will tell your health team if you are overweight. If you are carrying a few extra pounds you’ll be given advice on how to eat and exercise safely during your pregnancy.

Throughout your pregnancy you’ll be asked to give urine samples. These will be checked for any sign of protein or albumin. If this is found it can imply an infection which requires treatment or may be a sign of pre-eclampsia (a pregnancy complication that will require urgent treatment and sometimes medication).

During every antenatal visit you’ll have your blood pressure taken.

You’ll also be offered several blood tests. One will be to determine your blood group. This will be useful if you require any blood products during birth (due to heavy bleeding) or if your blood is ‘rhesus negative’ but your baby’s is ‘rhesus positive’. In such cases you’ll require extra monitoring. You’ll also be tested for anaemia which is common in pregnancy and can leave you feeling exhausted. If tests show you are anaemic you’ll probably be given iron and folic acid.

Your midwife will also offer you tests for common infections including rubella (German measles) sexually transmitted diseases including syphilis and HIV, and also hepatitis B an hepatitis C. All these conditions can impact on the baby and if you test positive for any of them you’ll health team will advise you on your treatment options.

You may require additional screening if there is a family history of certain genetic conditions. For example sickle cell or thalassaemia screening can be carried out via a simple blood test to be carried out before you are 10 weeks pregnant.

Ultrasound Scans

When you are around 8-14 weeks pregnant you’ll be offered your first ultrasound. This is sometimes called the dating scan as it will estimate your estimated date of delivery (EDD). The ultrasound will also check the baby’s size, will determine if you are carrying more than one baby, can show the position of the baby and the placenta, will check that the baby is growing normally and can detect most abnormalities.

You may be asked to attend the scan with a full bladder. Lubricating gel will be put on your tummy and a small handheld device moved across your skin. High-frequency sound is beamed to the womb to reflect back a picture which you’ll be able to see on a screen. This can be very exciting as it will be the first glimpse you’ll have of your baby.

A second ultrasound is carried out between 18-21 weeks. This scan checks for physical abnormalities, including checking the spine to rule out spina bifida. The sonographer who carries out the scan will be able to explain what he or she sees.

Screening for Down’s Syndrome

A variety of tests are available to check for the genetic disorder Down’s Syndrome. These include a blood test to check hormone levels and a nuchal translucency scan which involves an ultrasound to measure the pocket of fluid at the back of the baby’s neck. An increased amount of fluid indicates a higher chance of Down’s Syndrome.

Usually mothers will opt for ‘combined screening’ which occurs at between 11 and 13 weeks of pregnancy and involves a nuchal translucency scan together with blood tests to check for two pregnancy hormones called Papp-A and HcG. The results are combined with the mother’s age and the gestation of the baby.

If it is too late for the combined test, or if it is not offered in your area, you may be given a triple or quadruple test - both measure specific hormones in the blood to give you a risk measurement for Down’s Syndrome.

Following these tests (whether combined or just blood tests) you’ll be given a result which tells you the statistical likelihood of your baby having Down’s Syndrome. If the risk comes out as lower than 1 in 150 this is considered low-risk, if the results show the risk is greater than 1 in 150 then you will be offered a diagnostic test: either chorionic villus sampling (CVS) or amniocentesis.

Diagnostic Tests

Amniocentesis

Amniocentesis is offered from the time you are 15 weeks into the pregnancy. Ultrasound is used to guide a fine needle through the tummy into the amniotic fluid that protects the baby inside the womb. A sample of the fluid is taken and sent for testing. The fluid contains the same chromosomes as the baby so it’s these that will get checked. The test takes between 5-10 minutes to perform. The results will check not just for Down’s Syndrome but for other conditions such as cystic fibrosis. The results are usually available within three working days. The test can also reveal if you are expecting a boy or a girl.

Amniocentesis is associated with a 0.5-1% risk of miscarriage so is only carried out if the risk of a genetic disorder is considered to be higher than normal.

Chorionic Villus Sampling (CVS)

CVS sampling is usually performed from around 11 weeks of pregnancy. A fine needle is passed through your tummy into the placenta inside the womb. A tiny piece of the placenta is withdrawn to be tested for chromosomal abnormalities. The test takes 5-10 minutes and you may be given a local anaesthetic. You’ll receive the results within three working days.

A CVS has a 1% chance of miscarriage.

Although both an amniocentesis and CVS can yield results within three working days, the results can take up to three weeks if you require all the chromosomes to be checked.