Prenatal tests are a routine and vital part of pregnancy care. They help monitor the baby’s growth, detect any potential concerns early, and give both parents and healthcare providers valuable insights throughout the journey.
While it may feel overwhelming to navigate blood tests, ultrasounds, and screenings, understanding what each test does and when it should happen can bring clarity and confidence.
This guide outlines the most important prenatal tests, what they check for, and the ideal time to take them during pregnancy.
Why Prenatal Testing Matters
Prenatal testing helps ensure the health and safety of both mother and baby. Some tests confirm expected progress, while others can alert healthcare providers to complications or conditions that may need monitoring or treatment.
Testing also provides reassurance. Knowing that things are on track can ease anxiety and help parents prepare physically and emotionally for their baby’s arrival.
Types of Prenatal Tests
There are two main types of prenatal tests: screening tests and diagnostic tests.
Screening tests
These estimate the risk of certain conditions or abnormalities. They are noninvasive and typically involve blood tests and ultrasounds. If results show an elevated risk, a diagnostic test may be recommended to confirm or rule out the condition.
Diagnostic tests
These offer definitive results and are typically more invasive. They may involve collecting samples from amniotic fluid or placental tissue and are usually offered when screening tests indicate a possible issue.
First Trimester Tests (Weeks 1–13)
Initial Blood and Urine Tests (6–10 weeks)
These are typically ordered during your first prenatal visit.
What they check:
- Blood type and Rh factor
- Complete blood count (CBC)
- Immunity to infections (like rubella or varicella)
- Hepatitis B, HIV, and syphilis screening
- Urinalysis for protein, sugar, and infection
- Thyroid function (if needed)
These tests establish a health baseline for your pregnancy care.
First Trimester Screening (11–14 weeks)
This includes a blood test and an ultrasound known as the nuchal translucency (NT) scan.
What it screens for:
- Risk of chromosomal conditions like Down syndrome (trisomy 21) and trisomy 18
- Fluid collection behind the baby’s neck (linked to genetic conditions)
This is a noninvasive screening test and does not diagnose any condition definitively.
Noninvasive Prenatal Testing (NIPT) (from 10 weeks)
Also known as cell-free DNA testing, this blood test analyzes small fragments of the baby’s DNA in the mother’s blood.
What it screens for:
- Trisomy 21 (Down syndrome), trisomy 18, and trisomy 13
- Fetal sex (optional)
- Some sex chromosome conditions
It’s more accurate than the standard first trimester screening but is still considered a screening test.
Second Trimester Tests (Weeks 14–27)
Anatomy Ultrasound (18–22 weeks)
This is one of the most anticipated prenatal appointments and gives a detailed view of the baby’s development.
What it examines:
- Baby’s organs, limbs, and spine
- Placenta location
- Amniotic fluid levels
- Baby’s growth and estimated weight
It’s also when many parents choose to find out the baby’s sex, if desired.
Maternal Serum Quad Screen (15–20 weeks)
This blood test looks for substances related to the baby’s development.
What it screens for:
- Down syndrome (trisomy 21)
- Trisomy 18
- Neural tube defects (like spina bifida)
It’s often recommended if first trimester screening wasn’t completed.
Glucose Screening Test (24–28 weeks)
This test checks for gestational diabetes, a temporary form of diabetes that can develop during pregnancy.
How it works:
- You’ll drink a sugary drink and have your blood sugar tested after one hour
- If results are high, a longer glucose tolerance test may be needed
Managing gestational diabetes is essential for preventing complications during birth.
Third Trimester Tests (Weeks 28–40)
Group B Streptococcus (GBS) Test (35–37 weeks)
This test checks for GBS bacteria in the birth canal. While harmless to adults, it can be dangerous for newborns.
If positive, you’ll receive antibiotics during labor to prevent transmission.
Repeat Blood Tests (as needed)
Depending on earlier results or risk factors, your provider may repeat:
- Complete blood count (to check for anemia)
- HIV and other infection screenings
- Blood type and Rh antibodies (if you’re Rh-negative)
These ensure that both you and your baby remain healthy as delivery approaches.
Biophysical Profile (BPP) and Non-Stress Test (NST)
These may be performed in the final weeks if:
- The pregnancy goes past 40 weeks
- You have a high-risk pregnancy
- Your baby’s movement decreases
They assess fetal well-being through heart rate monitoring and ultrasound measurements.
Diagnostic Tests: When and Why They’re Done
Chorionic Villus Sampling (CVS) (10–13 weeks)
This test collects placental tissue to detect chromosomal conditions.
- Recommended when there’s a family history or high-risk screening result
- Has a small risk of miscarriage
Amniocentesis (15–20 weeks)
This involves collecting amniotic fluid using a thin needle.
- Provides accurate diagnosis for genetic conditions
- May also detect infections or assess lung development in later pregnancy
- Also carries a small risk of complications
These tests are optional and should be discussed with a genetic counselor or healthcare provider.
Are All Prenatal Tests Required?
Not all prenatal tests are mandatory. Some, like NIPT or diagnostic testing, are optional and depend on personal values, medical history, and provider recommendations.
Discuss with your provider:
- Your comfort level with screening vs diagnostic results
- Whether you want to know about potential genetic conditions
- What you would do with certain information
Your preferences matter, and informed consent is an essential part of prenatal care.
Preparing for Prenatal Tests
While most tests are simple and low-risk, it helps to be prepared.
Tips:
- Ask your provider ahead of time what each test is for
- Write down questions and bring them to appointments
- Schedule tests at times when your partner or support person can join you
- Stay hydrated and follow instructions for any fasting (if required)
Knowing what to expect reduces anxiety and empowers you in your care.
Final Thoughts
Prenatal testing plays a crucial role in ensuring a healthy pregnancy and delivery. By understanding what tests are available, when they’re done, and why they matter, you can approach each appointment with clarity and confidence.
Remember, every pregnancy is different. Work closely with your healthcare provider to choose the right tests for your needs and values.
You’re doing something powerful by being informed and proactive — for yourself, your baby, and your growing family.
