Genetic Testing During Pregnancy: Screening, Diagnosis, and What the Results Mean

Most people who are pregnant or planning a pregnancy get offered a set of genetic tests in the first weeks of prenatal care, and often only a short appointment to decide. The words come fast: cell-free DNA, carrier screening, nuchal translucency, amniocentesis. The choice is genuinely personal, the terminology is dense, and one term in particular, a “positive” result, is widely misread as a diagnosis when it usually is not. This guide to genetic testing during pregnancy covers what these tests look for, which ones exist and when they happen, what a positive result actually means, what testing costs, and how to think through what is right for you. Which tests make sense depends partly on how family health history guides screening. The guidance here follows current recommendations from ACOG, the Society for Maternal-Fetal Medicine (SMFM), ACMG, the CDC, and the FDA.

This article is general information, not medical advice. The decisions described here rest with you and your clinician.

Screening tests and diagnostic tests are not the same thing

A screening test estimates the chance that a baby has a genetic condition. A diagnostic test confirms it or rules it out. That difference drives almost everything else about how you read a result.

Screening tests include cell-free DNA screening (cfDNA, also sold as NIPT), first-trimester combined screening, and the second-trimester quad screen. They are safe for the pregnancy because they use a blood sample or an ultrasound, and what they give back is a probability, not a yes or no. Diagnostic tests are chorionic villus sampling (CVS) and amniocentesis. Both take a small sample of placental tissue or amniotic fluid and examine the fetal chromosomes directly, so they give a near-definitive answer, at the cost of a small procedure risk.

The current standard is to offer both paths to everyone. ACOG Practice Bulletin 226 established that prenatal screening and diagnostic testing should each be discussed and offered to every pregnant patient, regardless of age or baseline risk. ACOG has since issued a companion Practice Advisory that replaces Practice Bulletin 226, and SMFM replaced its earlier guidance with SMFM Consult Series #74 in late 2025. The through-line is unchanged: your age no longer decides which tests you are allowed to consider.

This replaced an older model that reserved cfDNA and diagnostic testing for patients considered high risk, usually meaning age 35 or older at delivery, an abnormal earlier screen, or a family history. Under current guidance, cfDNA should be routinely available to all obstetrical patients, and SMFM describes it as the most sensitive and specific screen for the common chromosome conditions in any population (a GRADE 1B recommendation, meaning a strong recommendation backed by moderate-quality evidence). Accepting or declining any of it is your decision, and a screen never closes the question by itself.

The genetic conditions prenatal tests look for

Prenatal tests look for two broad groups of conditions: chromosomal differences and single-gene inherited conditions.

Chromosomal differences, often called aneuploidy (an extra or missing chromosome), include Down syndrome (trisomy 21, an extra copy of chromosome 21), trisomy 18, trisomy 13, and differences in the number of sex chromosomes such as 45,X (Turner syndrome). Most of these happen sporadically, not because a parent carried them, and the chance of some rises with maternal age. Screening estimates the chance; CVS or amniocentesis confirms it.

Single-gene conditions are inherited. Many are recessive, which means a child is affected only if both parents pass on a change in the same gene. Cystic fibrosis, spinal muscular atrophy (SMA), sickle cell disease, and Tay-Sachs disease work this way. Fragile X syndrome follows an X-linked pattern. Carrier screening, done on the parents rather than the pregnancy, is how these are assessed.

Most of these conditions are uncommon. Down syndrome is the most frequent chromosomal condition at birth, with a US birth prevalence of about 15.55 per 10,000, or roughly 1 in 640, in 2016 to 2020, up from 12.78 per 10,000 in 1999 to 2001 (Stallings et al., 2024). You may still see the older figure of about 1 in 700. The CDC estimates about 5,775 US babies are born with Down syndrome each year. Carrier frequencies for single-gene conditions vary widely by ancestry: cystic fibrosis carrier frequency is about 1 in 25 in non-Hispanic White people and lower in several other groups (ACOG Committee Opinion 691). Cystic fibrosis itself affects roughly 1 in 2,500 to 3,500 US newborns (Rho et al., 2023). Sickle cell disease occurs in about 1 in 365 Black or African American births.

One caution about the maternal-age risk tables you may have seen. They are often quoted as the chance at the midpoint of pregnancy, not at live birth, and the two are not the same, because some affected pregnancies do not continue. And because there are far more births to people under 35, most babies with Down syndrome are born to mothers in that age group, even though the individual chance is lower.

Prenatal genetic tests are not designed for conditions that come from many genes and daily-life factors together, such as hereditary risk factors for type 2 diabetes or most heart disease. Those are estimated later in life with tools like polygenic risk scores for inherited conditions, not during pregnancy.

Your screening options and when they happen

The main screens, in the order they become available: carrier screening (best done before pregnancy), cfDNA from about 10 weeks, first-trimester combined screening at 10 to 13 weeks, and the quad screen at 15 to 22 weeks.

cfDNA analyzes fragments of placental DNA that circulate in the pregnant person's blood. It screens for trisomy 21, 18, and 13, and it can also report on the sex chromosomes. First-trimester combined screening pairs a nuchal translucency ultrasound (a measurement of fluid at the back of the fetal neck) with two blood markers, PAPP-A and hCG. The quad screen measures four blood markers in the second trimester. It is less sensitive than cfDNA for Down syndrome, but it has a feature cfDNA lacks: through one of its markers, MSAFP, it also screens for open neural tube defects such as spina bifida.

A few points changed with the 2025 guidance. Screening for sex-chromosome differences is now an opt-in choice that should follow a pretest conversation, because these results are the most likely to be misleading, for reasons covered in the next section. Routine screening for microdeletions (small missing pieces of a chromosome) and genome-wide copy-number screening are not recommended for the general population, because at low prior odds they produce more false alarms than true findings. The one exception SMFM allows is a targeted panel for the 22q11.2 deletion (DiGeorge syndrome), which has a positive predictive value of about 44 to 53 percent. Anyone who specifically wants microdeletion information is better served by diagnostic testing.

Sometimes cfDNA returns no result, often called a “no-call.” This happens in roughly 0.85 percent of tests, and it is not a null. A no-call is linked to a meaningfully higher chance of a chromosome condition. SMFM Consult Series #74 cites a relative risk near 130 for trisomy 21, 18, or 13 compared with a reportable result. It also tracks with higher body weight, earlier gestational age, and some pregnancy complications. Treat a no-call as a reason to talk with your clinician about repeating the test or moving to diagnostic testing, not a reason to assume all is well.

What a positive screening result actually means

A positive screen means the chance is higher than the general population's. It does not mean the condition is confirmed. How likely a positive cfDNA result is to be a true positive is called its positive predictive value, or PPV, and it swings widely depending on the specific condition and on maternal age.

For Down syndrome, cfDNA is very accurate as a screen: sensitivity is about 99 percent (it catches nearly all affected pregnancies) and specificity is above 99.9 percent (it rarely flags an unaffected one). Even so, because Down syndrome is uncommon, a share of positives are false. The chance that a positive result is a true positive runs from roughly half at age 20, to around 80 percent at 35, to over 90 percent at 40. At 35, then, something like 1 in 5 positive results is not a true positive. For trisomy 18 and especially trisomy 13, which are rarer, that figure is lower at every age.

The biology behind many false positives is worth understanding. cfDNA measures placental DNA, and the placenta and the fetus do not always match. When a chromosome difference is present in the placenta but not the fetus, it is called confined placental mosaicism (mosaicism means a mix of cell lines with different chromosomes in the same person or tissue). This is common enough with sex-chromosome results that up to about 59 percent of positive 45,X screens turn out to be confined to the placenta. That single fact is why sex-chromosome screening moved to opt-in.

The FDA issued a safety communication in 2022 making the same point in plain terms: no prenatal screening test of this kind is FDA-authorized or cleared, a positive result can reflect a chromosomal change in the placenta rather than the fetus, and results should be confirmed with diagnostic testing before any irreversible decision. Very rarely, cfDNA turns up something unexpected about the pregnant person's own chromosomes, and in rarer cases still, an unusual multi-chromosome pattern has been an early sign of a maternal cancer (SMFM Consult Series #74). Both are uncommon and are handled through follow-up, not alarm. A negative screen, for its part, lowers the chance substantially but never brings it to zero.

Diagnostic testing: CVS and amniocentesis

When you want a definitive answer, whether after a positive screen, an unexpected ultrasound finding, or simply by choice, CVS and amniocentesis provide it. CVS, done at about 10 to 13 weeks, samples placental tissue. Amniocentesis, done from 15 weeks, samples amniotic fluid. Both examine fetal chromosomes directly, and the sample is usually run with a chromosomal microarray, a test that detects small missing or extra pieces of chromosome that a standard karyotype and cfDNA both miss.

The concern most people bring to these procedures is miscarriage risk, and the number many still hear, about 1 in 100 to 1 in 200, is out of date. A 2019 meta-analysis (Salomon et al.) put the procedure-related loss risk at about 0.30 percent for amniocentesis (95 percent confidence interval 0.11 to 0.49) and about 0.20 percent for CVS (95 percent confidence interval -0.13 to 0.52), close to the background rate for people at the same starting risk. An earlier meta-analysis by Akolekar and colleagues estimated 0.11 percent for amniocentesis and 0.22 percent for CVS. Estimates vary by method, but the modern range lands near 1 in 300 to 1 in 500 or lower, below the older figure.

Results usually come in stages: a rapid result for the common trisomies within a few days, and the full microarray in one to two weeks. Diagnostic testing is also the right route for anyone who wants microdeletion or copy-number information, which the general-population screens are not built to provide reliably.

Carrier screening, and why your partner matters

Carrier screening is a blood or saliva test, ideally done before pregnancy, that shows whether you carry a recessive gene change. On its own it tells you little about a pregnancy. It becomes meaningful when both partners are tested: if both carry a change in the same gene, each pregnancy has a 25 percent chance of being affected, a 50 percent chance the child is a carrier, and a 25 percent chance the child inherits neither copy.

Guidance bodies genuinely differ on how wide the panel should be, and it is worth knowing both positions. ACOG (Committee Opinions 690 and 691, reaffirmed 2023) treats ethnicity-based, pan-ethnic, and expanded panels as all acceptable. It recommends offering cystic fibrosis and SMA carrier screening to everyone, along with a complete blood count and hemoglobinopathy screening. It adds fragile X screening for those with a family history or unexplained intellectual disability, and ancestry-based screening for conditions such as Tay-Sachs.

ACMG takes a wider line. It recommends a single pan-ethnic panel of 113 genes for everyone who is pregnant or planning a pregnancy, regardless of ancestry. The panel covers conditions with a carrier frequency of at least 1 in 200, fragile X included, and ACMG restated the approach in a 2024 laboratory technical standard. One caveat: the ACMG document is a “practice resource,” a lighter evidence bar than a full clinical guideline.

Partners can be screened at the same time (concurrent) or one after the other, with the second partner tested only if the first is a carrier (reflex, or tandem). Concurrent testing is faster and matters when time is short. A negative result lowers the chance of being a carrier but does not erase it, and detection rates are not equal across ancestries, which means the residual risk after a negative result is higher for some groups than others. Before either partner is screened, it helps to document your family health history, since known conditions on either side change which panel a clinician recommends.

Carrier frequencies give a sense of scale. SMA is about 1 in 54 pan-ethnic. Cystic fibrosis is about 1 in 25 in non-Hispanic White people, about 1 in 80 in Black or African American people, and about 1 in 100 in Asian American people. Tay-Sachs is about 1 in 30 in people of Ashkenazi Jewish descent versus about 1 in 300 in the general population, and enzyme testing catches carriers that DNA panels miss in non-Ashkenazi people. The FMR1 premutation linked to fragile X is found in roughly 1 in 150 to 1 in 290 US women (Owens et al., 2018). Figures for the rest are from ACOG Committee Opinion 691, linked above.

If both partners are carriers for the same condition, the options include in vitro fertilization with preimplantation genetic testing for that specific condition (PGT-M), donor eggs or sperm, prenatal diagnosis with CVS or amniocentesis, using the pregnancy time to prepare, and adoption. A genetic counselor can walk through what each would mean in your situation.

What genetic testing costs, and what insurance covers

With insurance, cfDNA and carrier screening are often $0 to about $300 out of pocket. Self-pay prices at major labs commonly run about $99 to $299. Without coverage, list prices and diagnostic procedures are much higher. The figures here are approximate ranges drawn from consumer cost-comparison sites and published lab price sheets, not official rates. Confirm your own numbers with your plan and, if relevant, your state Medicaid program.

Rough ranges: cfDNA self-pay about $99 to $299, with list prices of $800 to $2,000 or more; expanded carrier screening about $100 to $250 patient-pay, with list prices up to about $2,000; CVS or amniocentesis about $1,500 to $5,000 without insurance, though these are usually covered when medically indicated.

Coverage rules are uneven. Under the Affordable Care Act framework, non-grandfathered plans must cover services graded A or B by the US Preventive Services Task Force and the HRSA women's preventive services guidelines with no cost sharing, but routine screening for chromosome conditions is not on that guaranteed zero-cost list. Some plans still limit coverage to patients 35 or older or require a documented medical indication, even though clinical guidance dropped that age line years ago. Medicaid coverage of cfDNA also varies from state to state, so a test that is fully covered in one state may not be in another.

Questions worth asking before you consent: Is this lab in network? What is my expected out-of-pocket cost? Is there a patient-pay cap if insurance denies it? And if the result is positive, is the follow-up diagnostic testing covered? Broadly, cfDNA has moved from a test reserved for high-risk pregnancies to a first-line option in routine prenatal care, now covered by commercial plans and many state Medicaid programs for average-risk pregnancies.

Deciding what's right for you, and what to do with the results

There is no universally correct amount of prenatal genetic testing. The useful questions are practical: do you want a risk estimate or a definitive answer, would a result change your medical care or how you prepare, and how do you weigh a procedure-related risk of roughly 0.1 to 0.3 percent?

Some people want every data point available. Others decline screening entirely because a result would not change what they do. Both are reasonable. If you would want certainty after a positive screen, it is worth knowing that before you start, since it points toward diagnostic testing either way.

After a positive screen or a diagnosis, the next steps are a referral to a genetic counselor, often a maternal-fetal-medicine specialist, and a realistic timeline for any decision. Reputable condition-specific organizations can connect you with families living with the same diagnosis. Continuing the pregnancy is a valid choice, and the preparation time has real value: for medical planning, for the delivery team, and for the family.

Researchers are testing machine-learning tools to help interpret uncertain genetic variants and flag chromosomal changes on lab images. A systematic review of 38 studies through January 2025 found the work is still early, pointing to validation gaps, algorithmic bias, and no prospective clinical data yet. As of 2026, no major medical society recommends these tools for prenatal screening, variant interpretation, or counseling. Kaizen Health's assistant, Kai, does not interpret genetic results. It helps you keep test results and family history in one place, translate the terminology into plain language, and build a question list for your clinician and a genetic counselor.

A few things to carry into the appointment. Screening estimates a chance; diagnostic testing with CVS or amniocentesis confirms or rules out. A positive screen is not a diagnosis, and how likely it is to be a true positive depends on the condition and your age. Carrier screening works best before pregnancy and only describes risk to a pregnancy once both partners are tested. The added miscarriage risk from diagnostic testing is lower than the figure many people still quote. And the amount of testing you do is a personal choice, not a fixed protocol.

Bring your family health history and any earlier results to your first prenatal visit, ask which screening fits your situation, and keep prenatal test results and records organized so your whole care team sees the same picture you do.

References
[1] SMFM Consult Series #74, “Prenatal genetic screening,” Pregnancy, 2025. Accessed September 2026.
[2] ACOG Practice Bulletin 226, “Screening for Fetal Chromosomal Abnormalities,” 2020. Accessed September 2026.
[3] ACOG Committee Opinions 690 and 691, “Carrier Screening,” 2017, reaffirmed 2023. Accessed September 2026.
[4] Gregg AR et al., ACMG practice resource on screening for autosomal recessive and X-linked conditions, Genetics in Medicine, 2021. Accessed September 2026.
[5] ACMG laboratory technical standard for expanded carrier screening, Genetics in Medicine, 2024. Accessed September 2026.
[6] FDA, “Genetic Non-Invasive Prenatal Screening Tests May Have False Results,” Safety Communication, 2022. Accessed September 2026.
[7] American Family Physician, “Prenatal Screening and Diagnostic Testing,” 2020;101(8):481-488. Accessed September 2026.
[8] Stallings EB et al., “Population-based birth prevalence of Down syndrome,” Birth Defects Research, 2024. Accessed September 2026.
[9] Salomon LJ et al., “Risk of miscarriage following amniocentesis or chorionic villus sampling,” Ultrasound in Obstetrics and Gynecology, 2019. Accessed September 2026.
[10] Akolekar R et al., “Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling,” Ultrasound in Obstetrics and Gynecology, 2015. Accessed September 2026.
[11] CDC, “Down Syndrome,” Birth Defects. Accessed September 2026.
[12] CDC, “Data and Statistics on Sickle Cell Disease.” Accessed September 2026.
[13] Owens KM et al., “FMR1 premutation frequency in a large, ethnically diverse population,” American Journal of Medical Genetics Part A, 2018. Accessed September 2026.
[14] Rho J et al., cystic fibrosis incidence analysis, Journal of Cystic Fibrosis, 2023. Accessed September 2026.
[15] HRSA, “Women's Preventive Services Guidelines.” Accessed September 2026.