What is the Purpose of Prenatal Screening?

There is a lot more to the pregnancy journey than you think. Prenatal tests are important screening and diagnostic tests that help to diagnose health issues that could affect pregnant women and their babies. Early intervention allows us to treat and manage complications in the initial stages.

Regular prenatal tests must be done to look for health issues that may affect you and your baby. For example, a glucose tolerance test is used to identify gestational diabetes, which is manageable.

Understanding the purpose and types of prenatal screening can help expectant parents make better decisions about their pregnancy journey. This blog will explain what prenatal tests are, why they are done, and what you should know about them.

What are prenatal Tests? 

Prenatal tests are medical assessments that help evaluate the health and development of the unborn baby and identify potential risks or complications. They also assess the risk of disease and disorders to take preventive actions early. Many prenatal tests are available, from simple blood tests to advanced imaging techniques, each serving a unique purpose in monitoring maternal and fetal well-being.

What is the purpose of Prenatal Screening?

Prenatal tests are conducted for several reasons:

• To Assess Fetal Development—Prenatal testing's primary purpose is to monitor the baby's growth and development. Early in pregnancy, these tests can check the formation of essential organs, limbs, and other physical attributes.
• Detecting Genetic and Chromosomal Disorders- Many prenatal tests are designed to evaluate the risk of genetic or chromosomal disorders in the developing baby. 
• About 1 out of 700 babies is born with Down syndrome, and prenatal tests like NIPT can detect the risk of this condition with a high level of accuracy (around 99%).
• Identify Birth Defects and Structural Abnormalities- these prenatal tests can also detect physical abnormalities or congenital disabilities that may affect the baby’s development.
• Monitor Maternal Health- these tests also monitor the mother's health and ensure she remains healthy during pregnancy.

Gestational diabetes affects about 7% of pregnancies globally and can lead to severe complications like preterm birth, larger birth weight, and the need for a C-section. However, prenatal screening can help mitigate these risks.

• Detecting Pregnancy Complications—These tests help to identify complications that may arise during pregnancy. Conditions like preterm labor, preeclampsia, and intrauterine growth restriction (IUGR) can be monitored through various prenatal tests.

According to a study published by the March of Dimes, around 95% of pregnancies with abnormal prenatal screening results are followed up with diagnostic tests like amniocentesis, and most of these babies are born healthy.

Types of Prenatal Tests

Prenatal tests are important to monitor the health of the mother and baby during pregnancy. They are divided into two groups: diagnostics and screening tests.

• Screening Tests are noninvasive tests that help reveal the risk of certain health issues but do not provide definitive diagnoses. 
• Diagnostic Tests: These are more invasive and confirm whether a baby has any health issues.

Prenatal testing can be categorized into several types based on timing and purpose. Here’s a detailed look:

First Trimester Screening 

These tests are generally performed during the early stages of pregnancy (weeks 10 to 14) to assess the risk of genetic or chromosomal conditions.

• Blood Tests—These tests include pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG) levels to assess risk for conditions such as Down syndrome.
• Ultrasound- The nuchal translucency screening measures the fluid at the neck of the baby's neck to detect the risk of Down syndrome and other chromosomal abnormalities.

Second-trimester screening and Diagnostic Tests

These tests are performed between 15 and 20 weeks of pregnancy to monitor the baby’s development and detect potential congenital disabilities.

• Quad Screen: This blood test measures four specific substances: alpha-fetoprotein (AFP), hCG, estriol, and inhibin-A. It helps assess the risk for Down syndrome, neural tube issues such as spina bifida, and other genetic conditions.
• Anatomy Ultrasound (Level 2 Ultrasound)- A detailed ultrasound performed between 18 and 22 weeks to examine the baby’s organs, bones, and overall development. 
• Amniocentesis- This test analyzes the small sample of amniotic fluid removed from the uterus and analyzed for genetic and chromosomal disorders like Down syndrome, cystic fibrosis, and neural tube defects. 
• Glucose Screening- A test performed between 24 and 28 weeks to screen for gestational diabetes. It measures the mother's blood sugar levels after consuming a sugary drink.

Third-Trimester Testing:

Group B Streptococcus Screening: This test determines whether the mother carries Group B Streptococcus bacteria, which could potentially affect the baby during delivery.

Non-Stress Test (NST): This test monitors the baby's heart rate in response to its movements to ensure the baby is getting enough oxygen and is healthy.

Third-Trimester Screening and Diagnostic Tests

As the pregnancy progresses, tests in the third trimester (weeks 28 to delivery) help ensure that the baby and mother remain healthy.

Group B Streptococcus (GBS) Screening- This test is usually performed between 35 and 37 weeks. It checks for the presence of Group B strep bacteria in the mother's body, which can harm the baby during delivery. GBS is often found in healthy women in the following areas:

• mouth
• throat
• lower intestinal tract
• vagina

Who Should Take the Prenatal Tests?

All pregnant women should get prenatal screening. These tests help monitor the baby's health and development and ensure the mother remains healthy throughout the pregnancy. Here is who should take the prenatal tests- 

• Women aged 35 or Older
• Women with a family history of genetic disorders
• Women with pre-existing medical conditions 
• Women with previous pregnancy complications
•  Women carrying multiples (Twins, Triplets, etc.)
• Women with abnormal screening results
• Women with high BMI or Obesity

Key Takeaways

Prenatal screening provides essential information about the baby's and the mother's health, helping identify potential issues early. Understanding the purpose and implications of each test allows for better decision-making and preparedness for the birth process. Always consult with your medical professional to understand the best prenatal testing options for your situation.

Stay informed and aware about prenatal screening to ensure a healthier and happier pregnancy.