Prenatal Testing: Regular And Genetic Tests For Each Trimester

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From the time you conceive to the day of childbirth, you will be undergoing a series of tests that track your pregnancy. While some tests are routine prenatal checkups, others are voluntary and are performed under exceptional circumstances, on the recommendation of an obstetrician or genetic counselor.

Most of these tests are quick, painless and crucial to the health of the mother and the baby. MomJunction tells you about the tests you’ll have to undergo during the nine months of pregnancy.

What Is Prenatal Testing?

Prenatal testing refers to the series of medical assessments you have over the course of pregnancy. They include blood tests, invasive genetic tests, ultrasounds, vaginal swabs, and electronic fetal monitoring that help your doctor understand yours and your baby’s health (1).

  • Some tests are routine and are usually performed in every pregnancy. They analyze the baby’s progression and check if you are in good health for holding the baby until delivery. The tests also help your doctor understand the need for any special treatments.
  • Some other tests are optional and are done if you opt for it and you are at risk of some complication. These optional tests help determine if your baby has any genetic abnormality or congenital disabilities.
  • If certain health conditions run in your family, you should talk to your genetic counselor. The specialist can help you know about the possible birth defects or conditions which can have an impact on you and your baby’s health.

Next, let’s see the regular and the specific tests that you may undergo during pregnancy.

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What Are The Regular Prenatal Tests Performed During Pregnancy?

The following are the prenatal tests you have to take frequently during your pregnancy:

  • Blood pressure test: This is done to check if you have preeclampsia, a condition of high blood pressure and signs of organ damage mostly to liver or kidneys.
  • Urine test: This is done to check for kidney and bladder infections, and conditions such as preeclampsia. High level of protein in urine is a sign of preeclampsia.
  • Blood tests: They are done to find the blood type, Rh factor, and anemia. They also reveal infections such as hepatitis B, HIV, and syphilis.

Additionally, weight is also determined during every prenatal checkup to understand if your weight gain is ideal.

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What Are The Specific Types Of Prenatal Testing?

Prenatal tests are categorized into diagnostic and screening tests (2).

  • Screening tests: These tests identify your chances of having a baby with chromosomal abnormalities. They do not give definitive results but come with set parameters for results. If results are above or below a set level or measure, they are deemed positive and warrant further testing. There are no risks involved in doing these tests.
  • Diagnostic tests: These tests give definitive results if your baby has a genetic condition or congenital disability. The results are 99% accurate and usually follow screening tests. Diagnostic tests may pose some risks for you and your baby.

Keep reading for a detailed understanding of the tests done in each trimester of your pregnancy.

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First-Trimester Pregnancy Tests

The list of tests in your first trimester, which is from week zero to week 13 (months 1, 2 and 3) is as follows.

TestWhat it isHow it is doneThe risks involved
Blood testsThe initial blood screening test checks for:

  • Blood type
  • Rh factor
  • hCG levels
  • Sexually transmitted infection (hepatitis B, HIV, and syphilis)
  • Immunity to diseases such as German measles and chicken pox
  • Vitamin D deficiency
  • Blood sugar levels
  • Genetic risks for sickle cell anemia, spinal muscular dystrophy (SMA), cystic fibrosis, thalassemia, haemoglobinopathy, and other possible diseases
A blood sample is collected using a needle and syringe and submitted to the lab for testingNo risks involved other than the discomfort of pricking and bruising (3)
Urine testsA quick urine test checks for the following:

  • High levels of blood sugar that indicates gestational diabetes
  • High protein levels that indicate preeclampsia
  • Levels of red or white blood cells and bacteria indicating urinary tract infections (UTI) (1)
You will provide a sample, and the technician uses a dipstick or puts some drops into the testing strips.No risks involved
Chorionic villus sampling (CVS)It is done between the 10th and 13th weeks to detect birth defects such as:

  • Genetic disorders such as cystic fibrosis
  • Chromosomal disorders, such as Down syndrome

It is usually suggested for those who are at a greater risk of genetic disorders (4).

A small sample of placental cells is withdrawn for testing.Safe and reliable
Non-Invasive Prenatal Testing (NIPT)It is performed after nine weeks of pregnancy and checks for chromosomal disorders including:

  • Down syndrome
  • Edwards syndrome
  • Patau syndrome

It also detects Rh blood type and the gender of the baby.

A blood sample is used to look at cell-free DNA for signs of abnormalities (5)Very low risks are involved
UltrasoundThe first ultrasound is done between 6 and 9 weeks to:

  • Check the estimated due date
  • Detect the fetal heartbeat
  • Rule out ectopic or tubular pregnancies
  • Detect the number of fetuses
It is done using a transducer or wand over the abdomen that emits sound waves, which bounce off to give a picture on the screen.Very low risks are involved (6)
Nuchal translucency screeningIt is performed between 11 and 13 weeks of pregnancy to determine the risk of Down syndromeIt uses a unique ultrasound to examine the thickness of the fetal neck to calculate the probability of a chromosomal defect (7).No risk involved

Apart from these, there can be additional screening or diagnostic tests depending upon the condition of the individual.

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Second-Trimester Pregnancy Tests

These prenatal tests are commonly done in your second trimester (months 4, 5 and 6 of pregnancy):

TestWhat it isHow it is doneThe risks involved
AmniocentesisIt is performed between weeks 15 and 20 (sometimes much earlier) to check for:

  • Chromosomal conditions such as Down syndrome, Tay-Sachs disease, Sickle cell anemia
  • Neural tube defects such as spina bifida
A fine needle is inserted into the amniotic sac to draw the fluid containing fetal cells (8).Very-low risks are involved
Cordocentesis/ Fetal blood sampling/ Percutaneous umbilical cord sampling

It is performed as early as 17th week and checks for:

  • Anemia and blood oxygen levels
  • Maternal Rh antibodies
A fetal blood sample is withdrawn from the umbilical cord or fetusFetal risks and infections can develop (9)
Quad screenThis is performed in between 15 and 18 weeks to check for chromosomal disorders and neural tube defects.

It measures four substances that pass into the mother’s bloodstream from the fetus: alpha-fetoprotein, hCG, unconjugated estriol and Inhibin-A (10).

Uses blood sample for testingCompletely safe
Level 2 ultrasoundIt is done anytime between 18 and 20 weeks to see how the fetus is developing (11).It uses a transducer that sends sound waves to view the ultrasound images on the screen.No risks are involved
3D and 4D ultrasoundThey are usually done when the pregnancy seems to be complicated. They examine fetal abnormalities such as neural tube defects and cleft lip palate or anything specific.Multiple two-dimensional images are captured at different angles using the hand-held ultrasound device (12).
Glucose screeningThis is performed in between the 26th and 28th weeks of pregnancy to determine your risk of gestational diabetes.

Based on the results, you may need a glucose tolerance test (1).

You will be asked to consume a sweet drink followed by a blood test for glucose levels.No risks involved
Glucose tolerance testIt is done in between 26 and 28 weeks to detect gestational diabetes (1).You need to follow a strict dietary for a few days. Then, you fast for 14 hours before the test.

A blood test followed by consumption of sugary drink and serial blood tests helps detect the condition.

While you will have a good idea of how your baby is doing by this time, your provider will do a few more tests to make sure the baby arrives healthy and in the best condition.

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Tests During The Third Trimester Of Pregnancy

These prenatal tests are recommended in your third trimester (months 7, 8 and 9 of pregnancy):

TestWhat is itHow it is doneAre there any risks
Group B strep testIt is usually done between 35 and 37 weeks of pregnancy to screen for group B streptococcus bacteria (13).A swab is inserted into the vagina and another into the rectum, after which they are sent to a lab for testing and detecting any bacterial strains on the cells.No risks are involved
Nonstress testIt is performed anytime after the 28th week in the case of high-risk pregnancies, or if you are past your due date. It monitors the baby’s health and can show if the baby is in distress.A stretchable belt monitor is placed around the belly to track the fetal movements (14).
Biophysical profileIt is performed after 32 weeks of pregnancy when tests such as the nonstress test need a follow-up. It determines the risk of some possible complications and also decides if it is the time of labor.An ultrasound wand is used along with an elastic band with two sensors around the abdomen to detect the fetal heartbeat, body movement, breathing, amniotic fluid levels and muscle tone (15)No risks involved

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What Are The Optional Tests During Pregnancy?

Optional tests are performed on pregnant women who are at a risk of having a baby with a genetic disorder or congenital disability.

TrimesterOptional tests included
First
  • Cystic fibrosis
  • Chorionic villus sampling
  • Nuchal translucency screening
Second
  • Multiple marker screening
  • Amniocentesis
Third
  • Nonstress test
  • Biophysical profile

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What Are The Recommended Prenatal Tests For Women Over 35?

Genetic screening tests are usually recommended for pregnant women over 35. It is because the risks of chromosomal abnormalities increase with advancing age. The usual tests the obstetrician recommends are amniocentesis, nuchal translucency screening, chorionic villus sampling and anatomy ultrasound around the 20th week of pregnancy.

If results from these tests are abnormal, your doctor will refer you to a genetic counselor, who will help you understand the options and manage the condition.

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Understanding Prenatal Tests And Their Results

If your healthcare provider recommends prenatal tests, you should ask the following questions and more.

  • Why do I require the tests?
  • What will the results say?
  • Is it compulsory to get the test?
  • How accurate are the tests?
  • How long does it take for the test?
  • What are the risks involved?
  • How much does it cost?
  • Is there insurance coverage?
  • Where should I get the tests performed?

Getting answers to these questions will help you learn about the test, and cope with any fears and worries that you may have.

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Can You Refuse Blood Tests During Pregnancy?

You cannot decide whether you need a blood test or not. It is only your healthcare provider who can make the right decision.

Remember that these tests are done to ensure that you and your child are safe. The exact number of tests done or frequency of ultrasound varies from one woman to another, as it depends on their health condition.

Consult your doctor for any specific tests that you need.

Have any prenatal test experiences to share with us? Let us know in the comments section.

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Rebecca Malachi

She is a Biotechnologist with a proficiency in areas of genetics, immunology, microbiology, bio-engineering, chemical engineering, medicine, pharmaceuticals to name a few. Her expertise in these fields has greatly assisted her in writing medical and life science articles. With 8+ years of work experience in writing for health and wellness, she is now a full-time contributor for Momjunction.com. She is passionate about giving research-based information to readers in need. Apart from writing, she is a foodie, loves travel, fond of gospel music and enjoys observing nature in silence. Know more about her at: linkedin.com/in/kothapalli-rebecca-35881628
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