“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.
Prenatal Tests
It is natural for expecting parents to be concerned about the health of their unborn child. Prenatal diagnostics are a type of health screening that allows our doctors to run extensive testing on the fetus to detect whether any congenital malformations or disorders occur.
Early diagnosis, like with many diseases and medical disorders, can assist doctors to choose the best course of action and also allow parents to be prepared for their unborn child’s medical condition.
While most babies are born healthy, concerns such as these are natural. But take comfort in the fact that there are a number of tests available that will allay your fears. These can help identify potential health problems for you and your unborn child, some of which are treatable.
It is important to educate yourself and anticipate what you would do should you detect problems. Early detection means more time for treatment and planning various courses of action.
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Some prenatal tests are routine in pregnancies and are mostly screening tests. These include blood tests and ultrasounds that can only identify if your baby is likely to have certain conditions but cannot diagnose these with certainty.
Diagnostic tests, on the other hand, will either be suggested to you or you may opt to take them. They usually test for chromosomal disorders, which refer to an abnormality in the structure or number of chromosomes.
The chance of a child being born with these disorders increases if the expectant mother is older.
For example, the American College of Obstetricians and Gynaecologists found that 1 in 1,667 babies born to women in their early 20s have Down syndrome, but this number increases to 1 in 378 in women in their mid-30s and 1 in 106 for 40-year-old women.
Doctors would usually recommend older women or women with a family history of genetic disorders take these tests. However, an expectant can opt to take them as a precautionary measure as well.
Aside from the normal tests performed at each antenatal visit, such as blood pressure, weight, and urine dipstick for sugar and protein, the following tests may be performed if your doctor deems them necessary.
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.
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).
Diseases that emerge as a result of genetic alterations are known as genetic syndromes. Genes are DNA segments that contain protein-making instructions.
They have a wide range of functions, including defining cell shape, and structural functions, and controlling practically all metabolic processes.
Proteins are absolutely necessary for our bodies to function properly. A mutation in the genes, on the other hand, can lead them to lose their “code,” causing them to malfunction as a result of the altered information they acquire as they form. Genetic abnormalities may arise as a result.
How are genetic syndromes passed?
Genes are squeezed within chromosomes. The human genome’s 46 chromosomes are divided into 23 pairs of homologous chromosomes. The sex chromosomes, which determine an individual’s gender, are the last pair, and the rest is autosomal.
One or both parents can pass down a genetic mutation. Mutations, on the other hand, might occur by chance throughout our lifetimes.
During conception, each parent contributes a set of chromosomes, a unit from each spouse. If the groups of chromosomes change, it can be passed on to the children.
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.
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.
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 foetal heartbeat.
From about 8 to 10 weeks, ultrasonography 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.
Diagnostic tests for a chromosomal or genetic disorder
These are invasive tests that are typically used for the following reasons – some women who have previously had a kid with a chromosomal/genetic abnormality may want a test that is 100 per cent accurate, while those who receive a high-risk OSCAR or NIPT result may want a confirmatory test
- 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.
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 – 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 in 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 1-2 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%).
- 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 aged 35 and above or have a high risk of chromosomal abnormalities, such as if you have a family history of particular diseases.
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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.
Oral glucose tolerance test
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.
It 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.
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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.
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