How is NIPT (non-invasive prenatal testing) done?

NIPT is done with a simple blood draw from the mother's arm, typically after 10 weeks of pregnancy. The lab analyzes cell-free DNA fragments from the placenta circulating in the mother's blood to screen for trisomies 21, 18, and 13, as well as sex chromosome conditions.

How is chorionic villus sampling (CVS) performed?

CVS is done between 10 and 13 weeks. A doctor inserts a thin needle through the abdomen or a catheter through the cervix to collect a small sample of chorionic villi from the placenta. Ultrasound guides the procedure, and the sample is sent to a lab for full chromosomal analysis.

How is amniocentesis performed?

Amniocentesis is typically done between 15 and 20 weeks. A thin needle is guided through the abdomen into the amniotic sac to withdraw a small amount of amniotic fluid containing fetal cells. The cells are cultured and analyzed for chromosomal abnormalities or genetic disorders.

What is the difference between screening and diagnostic genetic tests?

Screening tests like NIPT and the quad screen estimate the risk of a condition but cannot confirm it. Diagnostic tests like CVS and amniocentesis provide a definitive yes or no answer about specific chromosomal abnormalities but carry a small risk of miscarriage.

How is NIPT (non-invasive prenatal testing) done?

NIPT is done with a simple blood draw from the mother's arm, typically after 10 weeks of pregnancy. The lab analyzes cell-free DNA fragments from the placenta circulating in the mother's blood to screen for trisomies 21, 18, and 13, as well as sex chromosome conditions.

How is chorionic villus sampling (CVS) performed?

CVS is done between 10 and 13 weeks. A doctor inserts a thin needle through the abdomen or a catheter through the cervix to collect a small sample of chorionic villi from the placenta. Ultrasound guides the procedure, and the sample is sent to a lab for full chromosomal analysis.

How is amniocentesis performed?

Amniocentesis is typically done between 15 and 20 weeks. A thin needle is guided through the abdomen into the amniotic sac to withdraw a small amount of amniotic fluid containing fetal cells. The cells are cultured and analyzed for chromosomal abnormalities or genetic disorders.

What is the difference between screening and diagnostic genetic tests?

Screening tests like NIPT and the quad screen estimate the risk of a condition but cannot confirm it. Diagnostic tests like CVS and amniocentesis provide a definitive yes or no answer about specific chromosomal abnormalities but carry a small risk of miscarriage.

How Is a Genetic Test Done in Pregnancy?

Q: How is carrier screening done in pregnancy?

Carrier screening is a blood test that checks both parents for recessive genes for conditions like cystic fibrosis, spinal muscular atrophy, and fragile X syndrome. It can be done before or during pregnancy. The lab sequences specific genes from the DNA in the blood sample.

Learn how genetic testing in pregnancy works in the US, from NIPT to CVS. Understand each step and order a comprehensive prenatal screening panel online.

Genetic testing in pregnancy is done through a simple blood draw or tissue sampling to analyze DNA from the baby or placenta, looking for chromosomal conditions like Down syndrome or single-gene disorders. In the US, most tests begin with a non-invasive prenatal screening (NIPT) around 10 weeks, followed by diagnostic procedures if needed. This guide explains the step-by-step process for each major test type, helping you understand what to expect and how to order a comprehensive screening panel.

Non-Invasive Prenatal Testing (NIPT): The First Step

NIPT, also called cell-free DNA testing, is the most common first-line screening in the US. It requires only a maternal blood draw—no needles near the baby. The lab isolates tiny fragments of placental DNA floating in your bloodstream. Because the placenta shares the baby's genetic makeup, analyzing these fragments reveals the baby's risk for trisomies (like Down syndrome) and sex chromosome variations. Results typically return in 7 to 10 days. NIPT is not diagnostic, so a positive result leads to a follow-up diagnostic test.

What Happens During the Blood Draw?

A phlebotomist draws about 10–20 mL of blood from a vein in your arm.
You do not need to fast or prepare in any way.
The sample is shipped to a certified lab where it undergoes DNA sequencing.
The lab measures the fetal fraction—the percentage of cell-free DNA from the placenta—which must be above a certain threshold (typically 4%) for accurate results.

First-Trimester Screening and the Quad Screen

Before NIPT became widespread, first-trimester screening combined a blood test (measuring PAPP-A and hCG) with a nuchal translucency ultrasound. The quad screen, done in the second trimester, measures four markers in maternal blood. These tests estimate risk but are less accurate than NIPT. Integrated screening combines both trimesters for a single risk estimate. All are still offered, especially when NIPT is not covered by insurance.

Diagnostic Tests: CVS and Amniocentesis

If a screening test suggests a high risk, your genetic counselor may recommend a diagnostic test. Chorionic villus sampling (CVS) retrieves a tiny piece of the placenta using a needle or catheter. Amniocentesis collects amniotic fluid containing fetal cells. Both are performed under ultrasound guidance and carry a small risk of miscarriage (roughly 1 in 300 to 1 in 500 for CVS, and 1 in 500 to 1 in 1000 for amniocentesis). Results take 1–2 weeks for full karyotype analysis, though some results may be available in a few days.

Test Type	When Done	Sample Required	What It Detects
NIPT (cell-free DNA)	10 weeks onward	Maternal blood	Trisomies 21, 18, 13; sex chromosome conditions
First-trimester screening	11–13 weeks	Blood + ultrasound	Risk of Down syndrome, trisomy 18
Quad screen	15–20 weeks	Maternal blood	Risk of Down syndrome, trisomy 18, neural tube defects
Chorionic villus sampling (CVS)	10–13 weeks	Placental tissue	Full chromosomal analysis (diagnostic)
Amniocentesis	15–20 weeks	Amniotic fluid	Full chromosomal analysis (diagnostic)

Carrier Screening: A Separate Blood Test

Carrier screening is a different type of genetic test done in pregnancy—or even before conception. It checks both parents for recessive genes that could cause serious conditions in the baby, such as cystic fibrosis, spinal muscular atrophy, and fragile X syndrome. The test uses a blood sample from each parent, and the lab sequences specific genes. If both parents carry the same recessive gene, the baby has a 25% chance of inheriting the condition. A genetic counselor can help interpret results and guide next steps.

Prenatal Paternity Testing

Though less common, prenatal paternity testing can be done using cell-free DNA from a maternal blood draw as early as 8 weeks. The lab compares fetal DNA with a cheek swab from the alleged father. This is a separate test from medical screening panels and is not covered by insurance.

What to Expect After Your Test

After any genetic test, results are reviewed by a genetic counselor who will explain the findings and discuss options. For screening tests, a low-risk result means the baby is unlikely to have the condition, but it is not a guarantee. For diagnostic tests, a normal result provides reassurance. If a condition is found, your counselor will help you understand the implications and connect you with specialists.

To get started on your prenatal genetic journey, you can order a prenatal screening panel online and receive your results quickly through a secure portal. This comprehensive panel includes NIPT and carrier screening for the most common genetic conditions, giving you peace of mind from the comfort of your home.