# 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.

*Published 2026-06-25 · By Priya Nair, MD*

The short answer
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](https://www.natera.com/womens-health/horizon-advanced-carrier-screening/what-it-screens/) 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](https://www.globenewswire.com/news-release/2024/06/04/2893107/15459/en/Myriad-Genetics-Launches-New-Universal-Plus-Panel-for-Foresight-Carrier-Screen.html) 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.

A note on MTHFR and preconception planning
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:

  Possible outcomes when both parents carry the same autosomal-recessive variant

      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](https://myriad.com/genetic-tests/foresight-carrier-screen/) 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.

## Sources

1. [Genetic Carrier Screening with Foresight](https://myriad.com/genetic-tests/foresight-carrier-screen/)
2. [Comprehensive Screening Options from Horizon](https://www.natera.com/womens-health/horizon-advanced-carrier-screening/what-it-screens/)
3. [Horizon test and pregnancy: Coverage, accuracy, pricing, and more](https://mynucleus.com/blog/horizon-test-pregnancy)
4. [Foresight Carrier Screen guide: Accuracy, conditions tested, and cost](https://mynucleus.com/blog/foresight-carrier-screen)
5. [Myriad Genetics Launches New Universal Plus Panel for Foresight Carrier Screen](https://www.globenewswire.com/news-release/2024/06/04/2893107/15459/en/Myriad-Genetics-Launches-New-Universal-Plus-Panel-for-Foresight-Carrier-Screen.html)
6. [Genetic Carrier Screening & NIPT Prenatal Testing Cost Assistance](https://myriad.com/affordability/prenatal/)
7. [Genetic Carrier Screening — Horizon Patient Information](https://www.natera.com/womens-health/horizon-advanced-carrier-screening/patients/)
8. [Personalized nutrition and precision medicine: A minireview of genetic polymorphisms COMT, FUT2, and MTHFR](https://pmc.ncbi.nlm.nih.gov/articles/PMC11664282/)

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Source: https://natalnew.com/prenatal-care/carrier-screening-before-pregnancy
Index: https://natalnew.com/llms.txt · Full text: https://natalnew.com/llms-full.txt