PEDIATRICS & CHILD CARE
What Is Pre-Natal Screening?
As the name suggests, pre-natal screening tests are procedures which are conducted during pregnancy. The main aim of these non-invasive prenatal tests is to know whether your baby is healthy, or may run the risk of suffering from any birth defects. During prenatal visits, your doctor will conduct a physical examination, and also suggest a few routine tests to ensure that all is well with you and your baby.
In the first few visits, our doctors will conduct the following pre-natal tests:
A Urine Test: This will be tested to confirm your pregnancy. During your subsequent visits, your doctor will keep asking you for a urine sample, to check if you may be suffering from any urinary tract infections or other conditions.
A Blood Test: This will be tested to map your blood grouping and typing, and help determine if you are suffering from any deficiencies for which supplements need to be prescribed. Also, a blood test will be able to determine if you have any sexually transmitted disease, like Syphilis or Hepatitis B, as some of these can be transmitted to your baby. In such cases, your doctor will also advise you on different forms of treatment that can reduce the chances of passing on this ailment to your child.
An Ultrasound: This will be conducted to give an indicative idea about your delivery date, as well as whether you are expecting twins or triplets.
What Are Trimester-based Tests?
Your doctor, during the first, second and third trimester of your pregnancy, will suggest that you go in for a set of prenatal diagnosis tests.
First Trimester Screening Tests
The First Trimester Fetal Diagnosis Tests include:
Early Blood Tests – Two types of prenatal blood tests are conducted – serum integrated screening and sequential integrated screening test. The purpose of these tests is to measure the levels of substances in the blood, namely the plasma protein A, which is pregnancy associated. Also, your doctor will also use the blood test to rule out any genetic ailments like cystic fibrosis, sickle cell disease and thalassemia, among others.
Ultrasound – Prenatal ultrasound tests offer you an image of the baby in the uterus. The main aim of ultrasound is to help you know the position of the baby, to find any potential abnormalities, to help you know how far the baby has come and so on.
Second Trimester Screening Test
The Second Trimester prenatal diagnosis tests majorly includes:
Blood tests – During the second trimester, a quad marker screening test is performed. The main aim of this test is to know whether there is any sign of birth defects like Down syndrome.
Glucose Screening– This prenatal test typically checks for any gestational diabetes. It is a condition which happens during pregnancy and is temporary. This type of problem could lead to the mother having a caesarian delivery.
Third Trimester Screening Test
The third-trimester screening test includes:
Group B testing – It is majorly performed during the 34-36 week. Your healthcare provider will swab your rectum and vagina. The samples would be sent to a lab to look for any bacteria. If the group B strep test is negative, no action is required. In case the group B strep test is positive, antibiotics are given during labour to prevent group B strep disease in your baby.
Bio-Physical Profile (BPP) – This, essentially, is a test that is a combination of both non-stress and ultrasound. This late pregnancy test helps you to know how is baby doing.
Quadruple marker test, also known as the Quad screen or simply the Quad test, is included in the second-trimester prenatal screening that is typically done between weeks 15 and 20 of pregnancy. The quad screen test derives its name from the fact that it measures the levels of four hormones found in all pregnant women’s blood:
- Alpha-fetoprotein (AFP) – a protein that is made by the developing baby
- Human chorionic gonadotropin (HCG) – a hormone that is made by the placenta
- Estriol – a hormone that is produced by the placenta and the baby’s liver
- Inhibin A – another hormone that is produced by the placenta
The quad test is done to evaluate the risk of carrying a baby who has any of the following conditions: Edwards syndrome (trisomy 18), Down syndrome (trisomy 21), Spina bifida and Anencephaly.
The quadruple marker screening test is a routine prenatal screening test. The test poses no risk of miscarriage or other pregnancy complications. The quadruple marker screening test is voluntary. Test results only show whether you have a higher risk of carrying a baby with Down syndrome, not whether your baby really has the condition. If the risk level is moderate or high, you have the option to follow the quad test with another test that’s more conclusive.
Before opting for additional testing, it is important to consider whether any strain caused by it may be worth it. Would you take the risk of choosing a more invasive follow-up test if screening tests come positive? How would you handle the results and would you manage the pregnancy differently based on a positive result
Before you consider taking any action on the basis of prenatal screening, make sure that an experienced physician or genetic counsellor at Women and Newborn Hospital has evaluated the results and you have had the opportunity to discuss it with them.
Pre-eclampsia is pregnancy-induced high blood pressure. It is one of the most common life-threatening conditions occurring in pregnancy. It occurs 1 in 50 pregnancies. High blood pressure can be extremely dangerous to both, the mother and baby. Currently, the only treatment is delivery. The delivery needs to be timed carefully as it needs to balance the condition of the mother and the maturity of the baby.
The probability of developing pre-eclampsia is increased by some factors including high body mass index (BMI), first pregnancy, and having any previous personal and family history of pre-eclampsia.
In addition to your 11-13 week scan you can opt to have a pre-eclampsia pregnancy screening for this potentially serious condition. There is vast evidence that early pre-eclampsia is associated with an increased risk to you and your baby’s health. Better maternal and fetal monitoring if detected high risk would lead to the early detection of pre-eclampsia from the clinical signs of the disease and where necessary medication can be given.
Pre-eclampsia screening process involves an ultrasound scan that measures the placental blood flow at 11-13 weeks of pregnancy in combination with mean arterial blood pressure, maternal history, placental growth factor (PLGF) and serum PAPP-A maternal blood marker.
A routine mid-trimester scan should be performed to check for not only the baby’s structural development but also growth, as close to 20 weeks as possible. At 23-24 weeks, it is important to check baby’s uterine artery dopplers, growth, your urine and blood pressure. At this stage, if everything is fine, your doctor will continue to check your urine and blood pressure throughout the pregnancy on a regular basis till you go into labour.
We, at Women and Newborn Hospital, know that the health of your unborn baby is your top priority. Therefore, we offer multiple screening tests including the Down Syndrome screening test. Not many know that Down syndrome can be easily detected while in the womb itself.
What Is Down Syndrome Screening?
Down syndrome is a genetic disorder that is caused when abnormal cell division results in extra genetic material from chromosome 21. Down syndrome causes a distinct facial appearance, intellectual disability, developmental delays and may be associated with thyroid or heart disease.
A test for Down Syndrome during pregnancy is offered to all women to assess the risk of the baby being born with this If your Down syndrome screening test shows a high risk, you will usually be offered a diagnostic test.
Combined First Trimester screening or NT scan: The vast majority of babies are normal. However, all women, whatever their age, have a small risk of delivering a baby with a physical or a mental abnormality such as Down syndrome. This condition is mainly looked for in the first-trimester screening.
Keep in mind that screening is not a diagnostic test; it is only a tool which indicates whether your baby has Down syndrome. The screening gives the probability of your baby having Down syndrome, trisomy 13, or trisomy 18.
The screening for Down syndrome involves an ultrasound assessment of the fetus for nuchal translucency (NT), which is a measurement of the fluid underneath the skin, alflow across the ductus venosus, the physiological valve regulating blood to the heart. It is advised to have the ultrasound at week 12 of pregnancy. However, the ultrasound can be performed at 11 weeks to 13 weeks and six days of pregnancy. It is a highly specialised ultrasound.
Blood Test – Although, the blood test can be performed up until 13 weeks and six days of pregnancy, it is recommended to have the blood test at week 10 of pregnancy. It analyses three chemicals found in the blood of all pregnant women – free beta-human chorionic placental growth factor (PLGF), gonadotropin (hCG), pregnancy-associated plasma protein-A (PAPP-A).
The NT measurement, nasal bone data and blood flow data are combined your age-related risk to arrive at one risk figure for Down syndrome and one risk figure for trisomy 13 or trisomy 18.
As this is only a screening test, a positive result (showing an increased risk) does not mean that your baby has an issue, only that further diagnostic tests are options for you to consider. Similarly, a negative or normal result (one that shows a decreased risk) does not mean that your baby will not have a chromosome abnormality. It is important to remember that most women will have normal babies, even if they are grouped as high risk.
If the screening test result positive, the following options are available:
- Diagnostic test by chorionic villus sampling (CVS) performed between 10-13 weeks,
- Diagnostic tests by amniocentesis are performed after 15 weeks
- Second-trimester maternal serum is drawn for screening after 15 weeks and a result combining first, and second-trimester is obtained
- Detailed anatomy ultrasound is performed at approximately 18-20 weeks.
Diagnostic tests such as CVS and amniocentesis can tell you whether or not a baby has a chromosome abnormality with more than 99% accuracy. While the final results of the chromosomal analysis may take 2-3 weeks, interim results may be available in a few days.
Couples or individuals may elect not to proceed with additional tests for various reasons. They may be comfortable with the results irrespective of the outcome or may choose to avoid any testing that poses a potential risk of harming the developing baby. It is important to discuss the risks and benefits of testing thoroughly with your doctor.