“Will my child be born with any abnormalities or birth defects, and will there be any complications?”
Pregnancy and becoming a parent come with a lot of surprises, but prenatal testing can help you know what to expect and prepare ahead for your child’s welfare.
There are so many tests and screenings a pregnant woman has to undergo to learn more about their unborn baby. In this article, we will discuss the required prenatal tests and screenings in each stage of pregnancy.
Why is Prenatal Testing Important
Prenatal testing plays a vital role in ensuring the well-being of both the expectant mother and the unborn child. Here are some reasons why any pregnant woman should seriously consider taking prenatal testing:
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Prenatal testing allows for the early identification of potential genetic disorders and birth defects, enabling timely medical interventions and treatment plans.
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With the information obtained from prenatal testing, expecting parents can make informed decisions about their pregnancy, including potential medical interventions, birth plans, and family support structures.
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Prenatal testing helps parents emotionally and mentally prepare for the arrival of a child with special needs, providing an opportunity to seek appropriate support, resources, and specialised care.
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Knowing the health status of the unborn child through prenatal testing can alleviate anxiety and uncertainty, allowing parents to focus on their own well-being and create a supportive environment for their baby.
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Prenatal testing results can assist in family planning decisions by providing information about the likelihood of passing on certain genetic conditions to future children.
Prenatal Testing
Expecting parents naturally have concerns about their unborn child’s health. Prenatal testing offers a range of diagnostic options to detect potential congenital malformations or disorders, providing early diagnosis and informed decision-making. Let’s explore the different types of prenatal testing, understand the distinction between screening and diagnostic tests, and empower ourselves with knowledge.
Screening tests are commonly performed during pregnancies and assess the likelihood of certain conditions. They include blood tests and ultrasounds, which can indicate potential risks but cannot provide a definitive diagnosis.
Diagnostic tests are either recommended by doctors or chosen by parents, aiming to identify chromosomal disorders with a higher level of accuracy. These tests are particularly advisable for older mothers or those with a family history of genetic disorders.
Screening tests provide an estimate of the likelihood of certain conditions, whereas diagnostic tests offer a more definitive diagnosis. It is essential to discuss with your healthcare provider to determine which tests are most suitable for your specific situation.
Genetic Testing During Pregnancy
While still in the womb, several tests can detect medical abnormalities in newborns. Others examine their DNA for signs of genetic diseases. Genetic carrier screenings can be done even before conception to predict the risk that their child would be born with a genetic disease.
The bulk of the tests are optional, but they can help you make health decisions and prepare for the arrival of your kid.
A carrier is someone who carries the gene for an illness but does not suffer from it. Genetic carrier screening assesses whether you and your partner both contain certain genes and, if so, how likely it is that they will be passed down to your children.
The tests can be used before or throughout pregnancy, but they are most helpful before.
Who should undergo genetic testing during pregnancy?
All pregnant women are advised to undergo these tests, but those who are more at risk for genetic problems are:
- Women over the age of 35
- Couples with a family history of genetic disorders
- Previous pregnancies with chromosomal abnormalities
- Couples from certain ethnic backgrounds with a higher risk of specific genetic conditions
- Abnormal ultrasound findings or blood test results
- Consanguineous couples (related by blood)
What is the screening for?
A doctor will take a sample of your blood or saliva for testing. The lab can look for genes for a range of diseases. But the most prevalent ones are:
- Tay-Sachs disease
- Fragile X syndrome
- Spinal muscular atrophy
- Cystic fibrosis
- Sickle cell disease
Ask your doctor if you fall into this category because some ethnic groups are more prone to be carriers of certain diseases. Carrier testing may assist non-Hispanic whites (cystic fibrosis), Eastern European Jewish people (Tay-Sachs disease, cystic fibrosis, and other diseases), and people from Africa, the Mediterranean, and Southeast Asia (sickle cell disease).
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Tests for Genetic Syndromes
Prenatal genetic testing can detect genetic disorders in our unborn child while she is still in the womb. Your gynaecologist may request extra tests based on risk factors such as age or family history. These screening and diagnostic tests are, of course, optional.
Aside from the prenatal test in the first trimester, the most common tests include amniocentesis and blood testing for genetic disorders.
First Trimester Tests
Blood tests
The blood tests include:
- A complete blood test to rule out anaemia and thalassaemia, a common inherited blood condition.
- Rhesus status and blood group – to determine rhesus compatibility between mother and foetus.
- Viral Hepatitis B
- Rubella (German Measles).
- Tests for syphilis and other venereal disease research laboratories (VDRLs)
- Human Immunodeficiency Virus (HIV)
Other blood tests may be performed based on the mother’s ethnicity and medical history. Screening for infections such as toxoplasmosis, a parasite disease, and cytomegalovirus, a common virus related to those that cause chickenpox and herpes simplex, as well as screening for carrier status of genetic disorders such as cystic fibrosis, sickle cell disease, and Tay-Sachs disease. Blood test results can take up to a week to come back.
Viability and dating ultrasound scans
An early viability ultrasound examination, performed between 6 and 8 weeks of pregnancy, can confirm that the pregnancy is developing healthily and can detect a foetal heartbeat.
From about 8 to 10 weeks, ultrasonography or ultrasound can be used to date the pregnancy and is accurate to within a week. This allows for the most precise calculation of the expected due date (EDD).
Screening tests for Down Syndrome (Trisomy 21) and other chromosomal problems
These tests are not required, but all pregnant women, regardless of age, should be offered them. There are several choices for this type of screening. It is important to note that screening tests are not diagnostic, which means that while they are often reliable, an ‘abnormal’ result will need to be validated by more intrusive testing procedures (see the section below on CVS and amniocentesis).
- One-stop clinic for assessment of risk for foetal anomalies (OSCAR)
This is made up of two tests. First, an ultrasound scan will be performed by a certified operator to determine the thickness of the skin in the foetal’s neck. This is referred to as nuchal translucency. The mother is then given a blood test.
The combined findings are analyzed using proprietary computer algorithm software, and a ‘risk score’ is created as a result. The test is done between 11 and 14 weeks and is roughly 90% accurate. Typically, test results are provided on the same day.
This is a collection of tests that identify foetal DNA (also known as cell-free DNA) in a mother’s blood sample. In reality, this DNA is derived from the placenta rather than the foetus. As a result, there is a slight probability that the results will be inaccurate.
These tests are available beginning at 9 weeks of age and screen for the following chromosomal disorders: Trisomy 21 for Down Syndrome, Trisomy 18 for Edwards Syndrome, and Trisomy 13 for Patau Syndrome. They can also detect gender and other genetic diseases like as triploidy and microdeletions.
While they cannot detect every genetic condition, they are quite accurate for the most prevalent ones, such as Down Syndrome, with a sensitivity of 97 to 99 per cent.
The test is available from numerous businesses, each with somewhat different screening panels for major genetic illnesses. Harmony, MaterniT21 Plus, Panorama, EasyDNA, and iGene are among the businesses involved.
- Chorionic Villus Sampling (CVS)
This test is usually conducted to detect chromosomal abnormalities such as Down syndrome and inherited disorders. The advantage of this test over amniocentesis is that it can be performed earlier, allowing parents to make decisions and receive counselling.
The test should be taken if you are above 35 years of age, had a child with a birth defect, have a family history of genetic disorders or had an abnormal screening test. Often performed between 10 and 12 weeks into pregnancy.
A needle is used to extract tiny placental tissue from your placenta during an ultrasound scan. The tissue is tested for birth defects because the baby originates from the placenta and the specimen would thus have the same chromosomes present in the unborn baby. Mild pain is felt during the procedure and local anaesthesia is used. Test results are ready within 1-2 weeks.
About 1% of CVS performed result in miscarriage. There are also risks of infection and birth defects developing if the test is done too early in pregnancy.
- Double marker test in pregnancy
The maternal serum screening, also known as the double marker test, is part of the first-trimester screening, which is a more extensive examination. It’s a predictive test, which means the results forecast the possibility of chromosomal abnormalities.
This test examines the blood for levels of free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein A. (PAPP-A). Female fetuses have 22 pairs of XX chromosomes, while male fetuses have 22 pairs of XY chromosomes in a typical pregnancy.
A double marker test and an NT scan are included in the first-trimester screening, which is optional. It is recommended if you are aged 35 and above or have a high risk of chromosomal abnormalities, such as if you have a family history of particular diseases.
Image Source: iStock
It’s important to remember that the result only tells you whether you’re at risk for trisomies. It is unable to determine whether or not your baby is abnormal. The time window in which the double marker test can be performed is limited. Your doctor will ask you to make an appointment near the end of the first trimester or very early in the second trimester.
Blood will be drawn between weeks 11 and 14, to be exact. The Double Marker Test is a simple blood test that doesn’t require any preparation. On the other hand, the doctor must be scared of the medications that will be administered before to the test.
The cost of a double marker test depends on your insurance coverage and where you live. While the test is optional, it may be covered by your health insurance policy.
Nuchal translucency is the appearance of fluid beneath the skin behind the fetal neck in the first trimester of pregnancy.
The term translucency is used regardless of whether it is septated or not, and whether it is confined to the neck or surrounds the entire fetus. In fetuses with chromosomal abnormalities, cardiac difficulties, and a variety of genetic illnesses, the NT thickness is increased.
NT screening can detect:
- around 80% of fetuses with trisomy 21 and other severe aneuploides
- with a false positive rate of 5%.
The NT scan can detect 70 to 80 per cent of Down syndrome babies. The detection rate of the NT scan paired with a first-trimester blood test is 79 to 90 per cent.
With the help of your doctor, you can determine whether the results indicate a high enough risk that you require CVS or amniocentesis for a definitive diagnosis.
- Thalassemia screening test
Before getting pregnant, partners are screened for Thalassemia with a test called haemoglobin electrophoresis or another test called HPLC (HPLC test).
A Complete Blood Count (CBC) blood test can be done to determine the number of red blood cells and any abnormalities in the haemoglobin content.
Second Trimester Tests
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Detailed foetal anomaly scan
This is normally done between the ages of 19 and 22 weeks. This test searches for structural abnormalities in the pregnancy that can arise even if no genetic abnormalities are found. The scan specifically looks for aberrant cardiac structures, facial clefts, head, abdomen, and limb size, placental position, doppler blood flow, cervical length, and amniotic fluid levels.
Foetal Blood Sampling (FBS)
This blood test is usually conducted to detect chromosomal abnormalities such as Down syndrome, inherited disorders, infections which can affect the foetus and anaemia or low platelet levels in the foetus. The major advantage of this test is that it can be carried out quickly, which is helpful when the foetus is in distress.
The test should be taken after an abnormality is noted on a screening test such as an ultrasound, when other test results are not conclusive or when you have been exposed to an infectious disease that could affect your foetus. The FBS is often performed between 18 and 23 weeks of pregnancy.
A fine needle is guided from the abdomen and into the uterus to extract blood from the foetus during an ultrasound scan. Mild pain may be felt during the procedure and local anaesthesia is used. Test results are ready within three to five days.
However, there is a risk as about 1% to 1.5% of FBS performed result in miscarriage.
Amniocentesis
This test is usually conducted to detect chromosomal abnormalities such as Down syndrome, inherited metabolic disorders and some foetal infections. Amniocentesis is usually performed later, between 16 to 20 weeks and also involves inserting a hollow bore needle through the abdomen under ultrasound guidance.
The test should be taken if you are above 35 years of age, had a child with a birth defect, have a family history of genetic disorders or had an abnormal screening test. Often performed between 15 and 20 weeks into pregnancy.
The doctor will remove some amniotic fluid through the abdominal wall of the uterus during an ultrasound scan with a very thin needle. These cells are grown in a special culture and analysed. You may experience slight pressure or pain, but usually nothing more. Test results are ready within 1 to 2 weeks.
Injury to the baby is rare. The risk of miscarriage is 1 in every 200 procedures. There is also a low risk of uterine infection and leakage of amniotic fluid.
Both CVS and Amniocentesis are invasive examinations that have a low chance of inducing miscarriage (CVS 0.5 – 1%; Amniocentesis 0.25 – 0.5%).
Oral glucose tolerance test (OGTT)
This test, which screens for gestational diabetes, is usually performed between 24 to 28 weeks. Gestational diabetes is a type of diabetes that affects some women during pregnancy. While most cases will resolve after delivery, women with gestational diabetes are at higher risk of developing Type 2 diabetes later in life.
OGTT involves 3 blood tests. You will begin the test in a fasting state and drink a 75g glucose drink. This is followed by 2 more blood tests 1 and 2 hours later. Results are usually available within 1 – 3 days.
Third Trimester Tests
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Regular and Doppler Ultrasound Scans
Some women may be required to have repeat ultrasound scans to monitor the progress of the foetus beginning late in the second trimester and continuing into the third trimester. This frequently includes Doppler ultrasound scans to check the flow of blood in the blood arteries nourishing the foetus.
Group B Streptococcus (GBS) test
This is a kind of bacterium that is found in the vaginal area of approximately 30% of women. GBS is normally harmless, but it can harm the baby as it goes through the birth canal during delivery. A vaginal swab is done, generally, around 35 weeks, and antibiotics are usually administered if it is positive for GBS.
Cardiotocograph (CTG)
During labour, this is a regular test that is used to continually monitor the baby’s heartbeat as well as the frequency and severity of any uterine contractions. A CTG may be prescribed by the doctor throughout the third trimester to monitor the baby’s health.
There are a variety of prenatal tests and scans available to monitor the health of both the mother and the baby during pregnancy, but not all tests are required. Your doctor can advise you on the ones you require.
Do not panic if your doctor does not ask you to undergo a certain test or if you haven’t done all the tests on the list. They will definitely let you know once they find an irregularity that needs to be confirmed through a test or a screening. But if you have any questions or concerns regarding these tests, do not hesitate to talk to your OB-Gynaecologist about it.
How Much Is Prenatal Testing in Singapore
Prenatal tests in Singapore can cost from $S50 to $S3000, depending on whether you will have it done in a government hospital, a private hospital or even a specialist clinic, and the type and number of tests your doctor advises you to undergo.
Pretty steep, right? But the good news is most of the tests are covered by Medisave and maternity insurance plans in Singapore.
Prenatal testing is super important for the health and well-being of both mums-to-be and their precious little ones. It gives us valuable insights to make informed decisions, catch any possible issues early on, and prepare for whatever may come our way.
Just remember to chat with your healthcare provider to figure out which tests are right for you and when to take them. Keeping those lines of communication open ensures that you and your baby get the best care possible and gives you that peace of mind you deserve!
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