Prenatal Care & Testing
Carrier Screening: What Expanded Panels Detect and When to Test
Expanded carrier screening can identify whether you and your partner carry recessive gene variants before a pregnancy is affected. Here is what the panels cover, how the 25% risk math works, and what testing actually costs in 2026.
Clinically reviewed · June 2026
Expanded carrier screening tests whether you or your partner carry a recessive gene variant that could affect a child if both parents carry the same one. Both ACOG and ACMG recommend it for all pregnancies. Testing before conception gives you the most options, but first-trimester testing is equally valid using the same panels.
Carrier screening is one of the quieter conversations in prenatal care — not because it is unimportant, but because most carrier results come back reassuringly low-risk and life goes on. For the roughly 1 in 22 couples who discover they are both carriers for the same recessive condition, however, the result opens a door to information that can meaningfully shape the decisions ahead. This guide explains what expanded carrier panels actually detect, how the genetics of recessive inheritance work in plain language, and what to expect in terms of cost and next steps in 2026.
This article is general health information, not personalized medical advice. Talk with your OB-GYN, midwife, or a certified genetic counselor about which panel is right for your situation and family history.
What does expanded carrier screening actually detect — and what does it miss?
Expanded carrier screening (ECS) uses next-generation sequencing (NGS) of a blood or saliva sample to look for pathogenic variants in genes associated with recessive conditions. A carrier carries one working copy of the gene and one variant copy. Carriers are almost universally healthy and unaffected — the risk arises only when two carriers for the same condition have a child together.
Modern expanded panels cover conditions that are medically significant, have a detectable carrier frequency in the general population, and have clinical actionability — meaning that a result changes reproductive decision-making. Every major panel includes:
- Cystic fibrosis (CF) — the most common life-limiting autosomal-recessive condition in people of European ancestry; carrier frequency approximately 1 in 25 among that population.
- Spinal muscular atrophy (SMA) — a progressive neuromuscular disease; carrier frequency approximately 1 in 40 to 1 in 60 in the general population.
- Sickle cell disease — a hemoglobin disorder particularly prevalent in individuals of African, Mediterranean, Middle Eastern, and South Asian ancestry.
- Tay-Sachs disease — a fatal lysosomal storage disorder with higher carrier frequency in Ashkenazi Jewish, French Canadian, and Cajun populations, though carriers exist across all ancestries.
- Fragile X syndrome — the most common inherited cause of intellectual disability; X-linked and screened differently from autosomal-recessive conditions.
- Duchenne muscular dystrophy — X-linked; female carriers can pass the condition to sons.
Natera Horizon is available in multiple tiers ranging from Horizon 4 through Horizon 274 and custom panels extending to 835 conditions. The Horizon 14 panel — a common starting point — screens 12 autosomal-recessive and 2 X-linked conditions; on average 1 in 9 individuals tested carries at least one variant. Myriad Foresight's June 2024 Universal Plus panel screens up to 272 genes and aligns specifically with the ACMG 2023 practice resource for carrier screening, including a custom assay for 21-hydroxylase-deficient congenital adrenal hyperplasia — a condition other panels commonly miss. The Foresight Universal panel is the only expanded carrier screening test in the U.S. with published analytical validation in a peer-reviewed journal, backed by data from more than 2 million patients; detection exceeds 99% across all major ancestries for the vast majority of genes on the panel.
What expanded panels do not detect: dominant conditions (such as Huntington's disease), chromosomal aneuploidies (Down syndrome, trisomy 18 — those are NIPT's domain), structural fetal anomalies, or variants of uncertain significance in genes not covered by the selected panel. Expanded carrier screening is not a genome-wide diagnostic test; it is a targeted, validated screen for the conditions on the chosen panel.
Separate from standard recessive-disease panels, many integrative practitioners recommend assessing MTHFR gene status before pregnancy. The C677T and A1298C polymorphisms reduce MTHFR enzyme activity and may impair conversion of synthetic folic acid to the active form of folate (5-methyltetrahydrofolate). A 2025 scoping review raised the concern that high supplemental folic acid specifically in C677T carriers may carry unintended metabolic risks — making the form of folate in a prenatal vitamin a meaningful personalization, not a fringe detail. ACMG does not currently recommend universal MTHFR screening, and any supplement changes should be discussed with your provider.
How does the 25% risk math work when both partners are carriers?
Autosomal-recessive inheritance is governed by Mendelian probability. Each carrier parent has one working allele (call it N) and one variant allele (call it v). At conception, each parent independently passes one allele to the child. The four equally likely outcomes are:
| Outcome | Alleles inherited | Probability per pregnancy | Status |
|---|---|---|---|
| Unaffected, not a carrier | N from each parent | 25% | No clinical impact |
| Carrier (like parents) | N from one parent, v from the other | 50% (two equivalent paths) | Healthy carrier; may pass variant to their own children |
| Affected | v from each parent | 25% | Will have the condition |
These probabilities are independent for every pregnancy. Having one unaffected child does not reduce the risk for the next. The 25% figure applies only when both biological parents carry a pathogenic variant in the same gene — if only one parent is a carrier, no child will be clinically affected (though 50% on average will be carriers themselves).
In practice, Myriad Genetics reports an at-risk couple detection rate of 1 in 22 for the Foresight Universal panel — the highest published rate in the category. This does not mean that 1 in 22 couples will have an affected child; it means 1 in 22 couples share a variant for at least one of the screened conditions, and each of their pregnancies carries that 25% probability for that condition.
For X-linked conditions like fragile X, the inheritance math differs: female carriers of the full mutation or premutation face a different set of reproductive considerations, and genetic counseling is particularly valuable before acting on an X-linked result.
When should you test, what does it cost, and what happens next?
Both ACOG and ACMG recommend that carrier screening be offered to all individuals who are pregnant or planning pregnancy, regardless of ethnicity. The previous approach — ethnicity-targeted screening (e.g., sickle cell only for people of African ancestry, Tay-Sachs only for Ashkenazi Jewish individuals) — missed a substantial fraction of at-risk couples because carrier variants exist across all ancestries. Universal expanded screening is now the clinical standard.
Preconception is preferred. Testing before conception gives you and your partner the widest menu of options if you are both found to be carriers: IVF with preimplantation genetic testing (PGT), prenatal diagnosis via CVS or amniocentesis, or informed expectant management with neonatal planning in place. Testing during the first trimester using the same panels is equally valid and remains clinically useful because CVS can still be performed, and amniocentesis is available throughout the pregnancy. If you are already in the second trimester and have not been screened, testing is still worth pursuing — the information guides neonatal preparation even if first-trimester timing has passed.
What testing looks like in practice: both Natera Horizon and Myriad Foresight accept blood or saliva samples (saliva is often collected via a kit mailed to your home). Results typically return within approximately two weeks. A positive result in one partner triggers expedited testing of the other biological parent. If both are carriers for the same condition, a referral to a certified genetic counselor is the standard next step — not cause for immediate alarm, but a prompt to have a deeper, structured conversation about your options.
Cost in 2026: Natera Horizon self-pay pricing runs approximately $249 for smaller panels and up to $449 for larger ones, with a price-transparency program that estimates your out-of-pocket cost after the sample arrives. Myriad reports that most insured patients pay $0 out-of-pocket, based on 12 months of claims data from major U.S. carriers; a personalized estimate is provided after sample submission. Both companies offer financial assistance programs. Most major commercial insurers and Medicaid cover at least a standard carrier-screening panel; coverage for very large expanded panels (200+ conditions) is more variable and worth confirming with your insurer before ordering. Both Natera and Myriad provide free access to board-certified genetic counselors — use this resource, particularly if a result is unexpected or if you are navigating a positive result without a specialist referral yet in hand.
Frequently asked
What is carrier screening and how is it different from NIPT?
Carrier screening tests you (and your partner) for recessive gene variants that could be passed to a child. A carrier is typically healthy — the issue arises only when both parents carry a variant in the same gene, giving each pregnancy a 25% chance of inheriting two copies and being affected. NIPT, by contrast, analyzes cell-free DNA from the placenta in the pregnant person's bloodstream to screen for chromosomal conditions — like Down syndrome — in the fetus itself. These tests answer different questions and are often both recommended. ACOG and ACMG both recommend expanded carrier screening for all individuals who are pregnant or planning pregnancy, regardless of ethnicity or family history. If you have already had NIPT, you may still need carrier screening; the two tests are complementary.
When is the best time to do carrier screening — before or during pregnancy?
Preconception testing is strongly preferred because it gives you and your partner the widest range of options if both are found to be carriers for the same condition. Those options can include in vitro fertilization with preimplantation genetic testing (IVF/PGT), prenatal diagnosis via CVS or amniocentesis, or simply preparing emotionally and medically for a potentially affected pregnancy. Testing during the first trimester is equally valid using the same panels — results typically return within two weeks — and can still allow time for diagnostic follow-up within that trimester. The important thing is not to delay: if you are already pregnant and have not been offered carrier screening, ask your provider at your next visit.
What conditions does expanded carrier screening detect?
Modern expanded panels cover dozens to hundreds of autosomal-recessive and X-linked conditions. Every major panel includes cystic fibrosis, spinal muscular atrophy (SMA), sickle cell disease, Tay-Sachs disease, fragile X syndrome, and Duchenne muscular dystrophy, among others. Myriad Foresight's Universal Plus panel screens up to 272 genes and was specifically designed to align with ACMG's 2023 practice resource for carrier screening. Natera Horizon ranges from 4-condition mini-panels up to panels covering 835 conditions. What expanded panels do not screen for: dominant conditions (like Huntington's disease), chromosomal aneuploidies (Down syndrome), or structural fetal anomalies — those require NIPT or an anatomy scan. Speak with a genetic counselor about which panel tier makes sense given your ancestry and family history.
How does the 25% risk actually work if both partners are carriers?
Autosomal-recessive inheritance follows predictable probability. Each carrier parent has one working copy of the gene and one variant copy. At conception, each parent passes one copy — randomly — to the child. The possible outcomes are: 25% chance the child inherits two normal copies (unaffected, not a carrier); 50% chance the child inherits one normal and one variant copy (carrier, like the parents, typically unaffected); and 25% chance the child inherits two variant copies and will be affected by the condition. These odds apply independently to each pregnancy — having one unaffected child does not reduce the risk for the next. This 25% figure applies only when both biological parents carry a variant in the same gene; if only one parent is a carrier, no child will be affected (though 50% may be carriers themselves). Myriad reports that approximately 1 in 22 couples tested with the Foresight Universal panel are found to be at-risk couples.
How much does carrier screening cost, and does insurance cover it?
Cost varies by panel and insurance status. Natera Horizon self-pay pricing runs approximately $249 for smaller panels and up to $449 for larger ones, and Natera operates a price-transparency program that estimates your cost once a sample arrives. Myriad reports that most insured patients pay $0 out-of-pocket based on a 12-month review of claims from major U.S. carriers, and offers a personalized cost estimate after sample submission. Both companies offer financial assistance programs for uninsured or underinsured patients. Most major commercial insurers and Medicaid cover at least a core carrier-screening panel; coverage for expanded panels (100+ conditions) is more variable. Always request a pre-authorization or a patient cost estimate before submitting your sample. Both companies also offer free access to board-certified genetic counselors to help interpret results, at no additional charge.
What happens if I test positive as a carrier?
A positive carrier result in one partner is common — Natera reports that roughly 1 in 9 individuals tested with the core Horizon panel carries at least one variant. By itself, a single-partner carrier result typically requires no clinical action beyond informing your partner. The next step is expedited testing of the other biological parent for the same condition. If both partners are carriers for the same condition, your provider will typically refer you for genetic counseling to discuss your options: preimplantation genetic testing with IVF, prenatal diagnosis via CVS or amniocentesis during pregnancy, or expectant management with neonatal planning. If you are already pregnant and both partners test positive, first-trimester CVS remains available for a definitive fetal diagnosis. Myriad Foresight offers unlimited access to more than 50 board-certified genetic counselors through its platform, a resource worth using when interpreting any positive result.