If your baby spends time in the neonatal unit (NNU), they will undergo routine tests and investigations. Here, we have explained some of these tests.

Blood Tests

Many conditions can be diagnosed using a blood sample.  Below are a number of blood tests that your baby may have during their time in the NNU.

Blood Culture

Blood cultures detect infections.  After taking a blood sample, the doctor sends it to the laboratory where it is cultured, i.e.  bacteria, if present, are encouraged to grow.  For a negative blood culture result, the sample must show no signs of bacterial growth after 48 hours of culturing.  If bacteria grow in the sample during this time, the medical team will start antibiotic treatment immediately.  Blood culturing also identifies which type of bacteria is causing the infection which allows the right antibiotic be used to fight the bacteria/infection.      

When taking blood samples for culturing, strict sterile conditions are used.  This minimises the risk of a false positive result because bacteria from the environment have gotten into the sample.  The doctor wears a sterile gown, gloves, and mask when taking blood for culturing.

C-Reactive Protein Blood Test

If C-Reactive Protein (CRP) levels are raised in the blood, it suggests infection or inflammation.  However, CRP does not tell us which bacteria are causing the infection or where in the body the infection is located.  It takes 6 to 8 hours for CRP levels to increase after the infection has started.  For this reason, antibiotic treatment may be started before the blood test result has been returned from the laboratory.  The decision to start treatment early depends on the baby’s risk of developing early onset neonatal sepsis.  Antibiotic treatment is usually stopped when 2 successive CRP blood tests are below the normal concentration, blood cultures remain negative after 24 hour of culturing, the baby appears well, and other worries of infection are low.  The accuracy of this blood test to detect infection is 99.7 % after 24 hour of life.

Full Blood Count

The blood is composed of many parts - red blood cells, white blood cells, platelets, water, haemoglobin, and gases.  A full blood count (FBC) is a set of tests that measures the number and quality of the various parts of the blood.  Therefore, a FBC screens for a number of illnesses.  For example, white blood cells are cells that multiply to fight infection. If the white blood cell count is high, it may be a sign of infection.  

Mom and Baby

If your baby spends time in the NNU they will undergo routine tests and investigations

Blood Gas Analysis

This test gives a lot of important information.  For example, it can inform how well the baby is breathing based on the oxygen and carbon dioxide levels in their blood.  It can show if the baby is jaundice from their blood’s bilirubin levels, and can inform on the baby’s nutrition and hydration status from glucose and electrolyte levels.

To run the test, the nurse takes 3 – 4 blood drops from a vein or capillary.  When a vein is used, the sample is taken during cannulation, i.e. the insertion of a thin tube into the vein for administrating medication.  If taken from the capillary, a heel prick is used.  A Blood Gas Analyser, which is in the NNU, analyses the blood in a few minutes.

Renal and Liver Function Tests

The kidney’s function is to clear waste products from the body into the urine as well as to maintain the fluid-salt balance in the body.  If your baby is dehydrated, the water content in the blood will be reduced and their blood will be more concentrated.  This will show as an increase in blood sodium (salt) levels above the normal range.  Your baby may undergo renal function tests to indicate how well the kidneys are functioning.

Liver function test (LFT) are used to indicate how well the liver is functioning.  This test gives important information on the level of bilirubin in the blood, i.e. jaundice level.

Blood Group Types and Antibody Tests

The Group and Cross Match Test examines what is your baby’s blood type: Group A, B, AB, or O.  This is very important to know if your baby needs a blood transfusion.  This test ensures your baby gets the correct blood type specific to them.

The Coombs Test looks for certain antibodies (proteins) in your baby’s blood. If present, these antibodies could interact with each other to cause the red blood cells to break down quicker than they should. This can sometimes lead to higher levels of jaundice in babies and these babies may need extra blood tests initially.

Equipment in the NICU

Many conditions can be diagnosed from a few simple tests

Urine Sampling

Urine samples can be used to test for many medical conditions.  In the NNU, urine samples are most often used for detecting the presence of infection.  To take a urine sample, a sterile ‘bag’ is placed around the baby’s genitals to catch urine.  This ‘bag’ is removed as soon as possible to prevent skin irritation from its adhesive.  If the sample is contaminated or leakage into the nappy occurs, a repeat sample is collected. 

The laboratory tests the sample. Sometimes,  when a quick guide for ordering further investigations is needed, the NNU staff test the sample with a ‘dip stick’.  Urine samples are not taken within the first 7 days of life unless toxicology, or another specialist investigation, is required.

X-ray

In the NNU, chest X-rays and abdominal X-rays are carried out by a radiographer using a portable X-ray machine.  The machine shows images of a baby’s lungs or abdomen.  These images are available to view within 5 to 10 minutes after the procedure.  Due to radiation exposure concerns, the use of X-ray is kept to a minimum and are only used when necessary.

Cranial Ultrasound Scan

An ultrasound scan uses ultrasound waves to create a picture of inside the body.  It does not use radiation.  A common use for ultrasound scans is to examine a baby’s brain for evidence of bleeding or other problems.  This is a cranial ultrasound scan.  Radiologists and neonatologists perform these scans. 

In the NNU of Cork University Maternity Hospital, all babies born less than 32 weeks’ gestation have a cranial ultrasound scan within the first 7 days of life, another at 1 month of age, and a final scan before discharge.  Some babies may require more scans during their stay in the NNU.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) scanners use magnetic fields to form a picture.  It does not use radiation hence it is safe for babies.  MRI provides a very detailed picture of the structure of the baby’s brain.  If your baby is to have a MRI, they will be brought to the MRI scanner in a special incubator.  A nurse will monitor them at all times.

To create a very detailed image, it is important that your baby stays as still as possible during the procedure.  To achieve this, your baby will be fed prior to the MRI and wrapped in blankets. This generally ensures the baby remains asleep during the MRI. 

 

 

If you have any concerns about any procedure planned for your baby, please do not hesitate to voice them.  Your baby’s doctor will answer all questions.  The medical team understand that waiting on results can be stressful, and will update you on the results as soon as they are available.