Headlines about gene editing can be both exciting and unsettling. You may have read that scientists can now "rewrite" DNA, or seen stories about babies born after their genes were edited. If you carry a genetic condition, or simply want to understand where reproductive science is heading, it is natural to wonder whether CRISPR embryo editing could one day be part of fertility care.

The honest answer is that genetic editing of human embryos is still a research topic, not a treatment. It is not offered in fertility clinics in the United States, and Hanabusa IVF does not offer it. What patients can use today are well-established genetic testing options that help identify embryos affected by certain conditions.

This guide explains what genetic editing means in this context, the current state of research, the ethical questions it raises, its regulatory status, and what all of this means for patients today.

What Genetic Editing (e.g., CRISPR) Actually Means in This Context

Genetic editing refers to tools that can change the DNA sequence inside a cell. The best known is CRISPR-Cas9, a system adapted from the way bacteria defend themselves against viruses. Scientists Jennifer Doudna and Emmanuelle Charpentier described how it could be used as a programmable editing tool in 2012, and they received the Nobel Prize in Chemistry in 2020 for this work (Nobel Prize in Chemistry press release, October 4, 2020).

In simple terms, CRISPR uses a guide molecule to find a specific spot in the DNA and an enzyme to cut it. The cell then repairs the cut, and scientists can sometimes steer that repair to change the sequence. Newer versions, such as base editing and prime editing, aim to make more precise changes without fully cutting both strands of DNA.

It is important to understand two very different uses:

• Somatic editing changes cells in one person's body, such as blood cells, to treat a disease. These changes are not passed on to children. In late 2023, the FDA approved the first CRISPR-based therapy for sickle cell disease (FDA press announcement, December 8, 2023), which edits a patient's own blood stem cells.
• Germline or heritable editing changes the DNA of eggs, sperm, or embryos. Those changes would be present in every cell of a resulting child and could be passed on to future generations. This is the type of editing that raises the most serious scientific and ethical concerns.

When people talk about CRISPR embryo editing, they are usually referring to germline editing.

Genetic editing versus genetic testing. These are often confused. Genetic editing tries to change an embryo's DNA. Genetic testing, such as preimplantation genetic testing (PGT), simply looks at an embryo's DNA to identify chromosomal or specific genetic differences. Testing does not alter anything. It helps patients and physicians choose which embryos to transfer.

The Current State of Research

Research on editing human embryos has moved quickly, but it remains limited to laboratory studies and has revealed significant challenges.

Early laboratory studies. In 2015, researchers in China reported editing human embryos that could not develop into pregnancies. In 2017, a team led by researchers at Oregon Health and Science University published a study in Nature describing an attempt to correct a disease-causing mutation linked to a heart condition in human embryos. These studies were conducted for research only, and the embryos were not transferred.

A widely condemned case. In 2018, a researcher in China announced the birth of twin girls whose embryos had been edited in an attempt to make them resistant to HIV. The announcement was met with near-universal condemnation from the scientific community, and the researcher was later sentenced to prison in China. The case highlighted the risks of moving to clinical use before safety and ethics are addressed.

Scientific obstacles. Studies have identified several problems that make embryo editing unsafe for clinical use today:

• Off-target effects: Edits may occur in unintended places in the genome.
• Mosaicism: Some cells in an embryo may be edited while others are not, creating a mix of cell types.
• Unintended changes at the target site: Some studies have found large deletions or rearrangements of DNA near the intended edit.
• Limited ability to verify: It is difficult to confirm that every cell in an embryo has been edited correctly without harming it.

Researchers continue to study early human development using embryo editing in tightly regulated laboratory settings. In the United Kingdom, for example, regulators have licensed research that uses gene editing to understand early embryo development, under strict limits and with no transfer for pregnancy.

"Gene editing is one of the most remarkable scientific tools of our time, but in human embryos it is still a research question. Our responsibility to patients is to offer what is proven safe and effective today." - Dr. Lyndon Chang, Medical Director at Hanabusa IVF

What would need to change before clinical use

For embryo editing to ever be considered for clinical use, researchers would need reliable ways to make only the intended change, confirm that every cell carries it, and follow children over many years to understand long-term health. Broad agreement among scientists, regulators, and the public would also be required. None of these conditions has been met today, and most experts expect any clinical role, if one ever develops, to be many years away.

At Hanabusa IVF, we follow developments in reproductive science closely so that patients can rely on evidence rather than headlines. You can learn more about research at Hanabusa IVF on our research page.

Ethical Considerations

Even if the technical problems were solved, germline editing raises deep ethical questions that society is still working through.

Safety for future generations. Changes made to an embryo would affect not only the child but potentially their descendants. Long-term effects are unknown.

Consent. A future person cannot consent to changes made to their genome before they exist.

Medical need versus enhancement. Many people see a difference between correcting a serious disease and making changes for non-medical traits. Drawing that line is difficult, and critics worry about a slide toward "designer babies."

Existing alternatives. For many couples at risk of passing on a genetic condition, preimplantation genetic testing already allows them to select unaffected embryos. This raises the question of when, if ever, editing would offer a meaningful advantage.

Equity and access. There are concerns that advanced reproductive technologies could widen social inequalities if only some people can access them.

Social and disability perspectives. Some disability advocates have raised concerns that efforts to "edit out" conditions could affect how society values people living with those conditions.

International scientific summits on human genome editing, held in 2015, 2018, and 2023, have consistently concluded that heritable human genome editing is not acceptable at this time. These discussions continue, and they involve scientists, ethicists, patients, and the public.

Regulatory Status

Rules vary around the world, but heritable genome editing is not permitted for clinical use in most countries.

In the United States:

• Federal law prevents the FDA from reviewing applications for clinical trials that involve intentionally creating heritable genetic modifications in human embryos. As a result, heritable editing cannot legally proceed toward clinical use.
• Federal funding cannot be used for research that creates or destroys human embryos, although privately funded laboratory research may take place under institutional oversight.

Internationally:

• Many countries prohibit heritable genome editing by law.
• Some countries, such as the United Kingdom, allow tightly regulated laboratory research on embryos for a limited time after fertilization, but do not allow edited embryos to be used for pregnancy.

These rules mean that no fertility clinic in the United States can offer embryo gene editing as a treatment.

What This Means for Patients Today

If you are concerned about passing on a genetic condition, or you simply want to give your embryos the best possible start, there are proven options available now.

Preimplantation genetic testing (PGT). PGT involves taking a small sample of cells from an embryo, usually at the blastocyst stage, and testing it in a specialized laboratory.

• PGT-A screens for an abnormal number of chromosomes.
• PGT-M tests for a specific inherited condition when the family's genetic variant is known.
• PGT-SR looks for structural chromosome rearrangements, such as translocations.

You can learn more about each test in our guide to PGT-A vs. PGT-M vs. PGT-SR, and on our PGT page. Hanabusa IVF works with an established genetics laboratory for testing, described on our page about Gattaca, our PGT-A testing provider.

Genetic counseling. If you or your partner carry a known genetic condition, genetic counseling can help you understand your risks and options, including PGT-M, donor eggs or sperm, or other paths.

Carrier screening. Before treatment, carrier screening can identify whether you and your partner carry variants for certain inherited conditions.

At Hanabusa IVF, genetic testing decisions are individualized. Not every patient needs PGT, and our "One Size Doesn't Fit All" philosophy means we discuss the benefits and limitations of testing based on your history, age, and goals. We care for patients with complex histories, such as diminished ovarian reserve or recurrent pregnancy loss, as well as those just beginning their fertility journey.

"When patients ask about gene editing, I often find that what they really want is reassurance about their embryos' health. We can talk through the testing options that exist today and decide together what makes sense." - Dr. Diana LeBlanc, a Fertility Specialist at Hanabusa IVF

If you are curious about other emerging areas of reproductive science, our article on in vitro gametogenesis and the future of fertility explores another field that is still in the research stage.

Frequently Asked Questions

What is the difference between genetic editing and genetic testing (PGT)?

Genetic editing tries to change the DNA of an embryo. Genetic testing, such as PGT, only examines an embryo's DNA to identify chromosomal or specific genetic differences, without altering it. PGT is available today, while embryo editing remains a research topic.

Is embryo genetic editing available in fertility clinics today?

No. Heritable genome editing is not available as a treatment in the United States, and federal law prevents it from moving toward clinical trials. Most other countries also prohibit it.

Does Hanabusa offer genetic editing services?

No. Hanabusa IVF does not offer embryo genetic editing. We offer established genetic testing options, including PGT, and individualized guidance about whether testing is right for you.

What are the main ethical concerns around embryo gene editing?

Key concerns include unknown long-term safety for future generations, the inability of a future person to consent, the line between treating disease and enhancement, equity of access, and the fact that genetic testing already offers alternatives for many families.

What genetic screening options are available today?

Current options include carrier screening before treatment and preimplantation genetic testing of embryos: PGT-A for chromosome number, PGT-M for specific inherited conditions, and PGT-SR for structural rearrangements. Genetic counseling can help you decide what fits your situation.

Interested in the Genetic Testing Options Available Today?

CRISPR embryo editing is a fascinating and fast-moving area of science, but it is not a fertility treatment today. Serious scientific, ethical, and regulatory questions remain, and international experts agree that heritable editing is not appropriate at this time.

What patients can use now are proven genetic testing options, chosen thoughtfully and individually. Interested in the genetic testing options available today? Learn more about PGT-A, PGT-M, and PGT-SR testing.

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