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Pregnancy Screenings and Scans 

Prenatal screening tests encompass various tests that your doctor recommends for you during pregnancy. There are additional tests and scans that you may want to do to get rid of certain doubts.

These screening tests begin at your first prenatal appointment and are mostly non-invasive. A screening test only tells you if you are at risk, or high probability of a particular condition.

Once you notice the early signs of pregnancy and take a test to confirm pregnancy, the next step is to go through what to do after a positive pregnancy test, a large part of which is screenings and scans. Listed below is details of what each one entails: 


The first-trimester screening or 12-week scan is a prenatal test that gives you information at an early stage about certain chromosomal conditions that your baby might be at risk at. This focuses particularly on trisomy 21, commonly referred to as Down syndrome, and trisomy 18 also known as chromosome 18.  The 12-week scan tells you the number of babies you are having, calculates the age and the delivery date of the baby and screens the baby for any common chromosomal conditions. The First trimester screening is a combination of two tests – an ultrasound and a blood test. It is typically done between the 11th and 14th week.  

  • There is a blood test that measures pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (HCG) and indicates the level of these pregnancy-specific- substances in the mother’s blood. 
  • An ultrasound exam is conducted for nuchal translucency. This measures the size of the clear space in the tissue at the back of the baby’s neck. 

What are the risks and what should you do to prepare yourself for the test?  

The First trimester screening is a non-invasive routine prenatal test. This 12-week scan does not put you at any risk of miscarriage or pregnancy complications. It is a regular test and does not require any special prep – you can continue to eat and drink as you were before the blood test and the ultrasound. You can resume your day-to-day activities right after the screening.  

Why is the first trimester screening done?  

The 12-week scan is done to inform you about the risk of carrying a baby with Down syndrome. Besides, this test evaluates the risk of Trisomy 18. Down syndrome leads to permanent damages in development – both social and mental and is associated with several physical impairments. Trisomy is fatal and results in death by age 1. 

This is one of the first prenatal screening tests and gives you results at an early stage during the pregnancy. The first trimester screening is an optional test and evaluates if the mother is at an increased risk of carrying a child with Trisomy 18 or down syndrome. It does not tell you if the baby will be born with one of these conditions.  

This first trimester screening sets the course of action for the future pregnancy – taking decisions about other diagnostic tests, mentally preparing you for caring for a child with special needs (if the baby is at a high risk of chromosomal abnormality) and taking treatment and management decisions post-delivery.  

Please note that this is just an indicative test – a low risk does not guarantee that baby will be born without any abnormalities and similarly a high risk is no sure shot reason for your child to have down-syndrome.   

If everything comes out fine during the tests, it is believed to be one of the most amazing moments for the parents to be. You see your baby for the first time, you get to hear the heartbeat and if you are lucky, you may see some movements as well.  

Other screening tests are done during the pregnancy which are combined with the first trimester screening to improve the detection of the test. This process is called integrated screening 

Other screening tests are done during the pregnancy which are combined with the first trimester screening to improve the detection of the test. This process is called integrated screening


The second trimester screening popularly known as the 20th-week scan or anatomy scan is scheduled between Week 18 and Week 22 of your pregnancy. It checks the growth and development of the baby, the positioning of the placenta, identifies the sex of the baby, scans the body parts and checks any spinal issues like spina bifida, limb abnormalities and heart defects. It may also indicate if your baby has a genetic condition.  

The second trimester screening also involves a blood test known as quad screen done anywhere between Week 15 and Week 20 of the pregnancy. This screening evaluates the risk of carrying a baby with chromosomal abnormalities such as Trisomy 18 and Down syndrome or any neural defects such or abdominal wall defects. 

  Why is the 20th-week scan done?  

  • Evaluate the baby’s growth. Your health care provider takes measurements during the ultrasound to determine if your baby is growing at a normal rate.  

The spine is checked to ensure that the vertebrae are aligned and covered by the baby’s skin.  It is used to monitor your baby’s movement, breathing and heart rate which should range between 120 to 180 beats per minute 

  • Assess the risk of placenta previa – The placenta is the source of vital nutrients and oxygen-rich blood for the baby. The ultrasound studies the amniotic fluid levels (the fluid that surrounds the baby in the uterus) and any placenta complications that require special attention. Too little or too much of the fluid is not good.  
  • Identify any birth defects or abnormalities – An ultrasound helps to check for congenital heart defects which is extremely common by evaluating the function of the four chambers of the heart.  

The scan brings to light any potential genetic disorders like Down Syndrome or Trisomy 18. The technician may be able to spot a cleft lip and sometimes even a cleft of the palate. They ensure that the kidneys are working fine by checking for liquid in the bladder.  

  • Investigate and possible complications – They check for premature labour possibilities using a transvaginal ultrasound wand to inspect the cervix. Ideally, it should be closed and long, however, if it is shortened or/ and opened the risk of premature labour is high 

Why is the quad screen done?  

The quad screen is done to evaluate the following medical conditions in the baby you are carrying: 

  Down syndrome (Trisomy 21): This is a chromosomal abnormality that causes lifelong intellectual and developmental impairment. It also leads to health problems for certain children.  

  Trisomy 18: Often fatal by age 1 this chromosomal disorder causes severe delays and abnormalities in the development of the structure of the body.  

  Spina bifida: Spina bifida is a birth defect in the spinal cord and the bones of the spine. It occurs when a part of the neural tube is unable to develop or close properly.  

  Abdominal wall defects:  these are birth defects where the baby’s abdominal organs or intestines stick through the belly button. 


The third trimester tests are diagnostic tests and ensure the well-being of the baby and mom-to-be. The various tests that are a part of the third trimester screening are:  

  Biophysical profile: This ultrasound is done to check if the baby is getting enough oxygen.  

  Group B streptococcus screening: This is done between the 35th to 37th week using Vaginal and rectal swabs to detect the presence of group B strep bacteria. This bacterium is the leading cause of life-threatening infections in newborns. It can also lead to impaired vision and hearing and intellectual disability. If a woman tests positive, she is prescribed antibiotics to prevent the baby from contracting the infection at birth.  

  Nonstress test: This is a weekly test done for many high-risk pregnancies – if the woman is carrying twins or more, has high blood pressure or diabetes.  

A fetal monitor is strapped across the mother’s abdomen and it measures the baby’s heart rate as it moves. This test is also used to monitor overdue babies.  

  Electronic fetal heart monitoring: As the name suggests this test monitors the heart rate of the fetus during pregnancy, labor, and delivery. This test ensures the well-being of the fetus and is done post 20 weeks.  

  Contraction stress test: This is prescribed for high-risk pregnancies. It involves the usage of a fetal monitor to measure the baby’s heart rate as a response to nipple stimulation or contractions caused by oxytocin (Pitocin). The measurements are used by the Doctor to predict how well the baby will cope with labor stress. 


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