When does an embryo become a person?

The question of when human life begins has been debated for years: At the time of fertilization? Of implantation? Or birth? The definition of human life itself varies widely among practitioners in the fields of philosophy, theology, psychology, sociology, law and politics.

Defining human life at the time an egg fertilizes is globally a vanishing rarity. Most countries do not grant legal status to the human embryo for at least 14 days after fertilization. But some in the US are trying to change existing laws and grant fertilized eggs the same rights as a live person. Lets dive further into understanding what an embryo is (and what it isn’t) and then we’ll talk about why changing the classification of a fertilized egg can cause a ripple effect with many downstream changes in all aspects of our society.

A human embryo is a group of cells, it does not have different organs, it has no heart or brain or the ability to live outside of a uterus. The cells have the potential to grow and differentiate into different types of organs if placed in a uterus, eventually making a human if the cells grow successfully and the fetus is born. But on their own, they are simply cells and not a human being. Bone marrow stem cells also have the ability to differentiate into various tissues, but we don’t consider bone marrow stem cells to be human beings.

Fertility doctors and scientists generally regard human embryos as potential life. A human embryo must successfully implant onto a uterine wall to continue growing. Research on early pregnancy loss has shown that a very high number of embryos temporarily implant, with an estimated 40% to 60% of embryos miscarrying, often before the woman even knows she’s pregnant.  There are so many things that must happen correctly, naturally, for a fertilized egg to produce a liveborn human.

In vitro fertilization is a therapy that parallels the natural process of fertilization and embryo implantation. Since natural fertilization is prone to many embryos stopping growth naturally due to abnormalities, IVF sees the same phenomena, with many fertilized eggs not ultimately producing an embryo that is healthy or suitable for transfer to the uterus. IVF also allows couples to test for chromosome imbalances in embryos, conditions that most often cause failed IVF transfers or miscarriage if the embryo is placed in the uterus.

In the IVF procedure, reproductive endocrinologists/infertility specialists (REIs) stimulate egg growth with medications, yielding anywhere from one or two eggs (oocytes) to dozens available through transvaginal retrieval from the ovaries. On average, REIs expect 70% to 80% of eggs to fertilize during an IVF cycle; but only about one-third will develop into embryos. Many of these embryos have the ability to produce an ongoing pregnancy, but many also have genetic abnormalities; if these abnormal embryos are transferred to a woman’s uterus, it most often results in a failed IVF cycle or miscarriage but can also result in birth of a child with genetic disorders.

Given the high rate of abnormal fertilization that is part of natural human reproduction, IVF improves natural human reproduction by giving more eggs a chance to fertilize, increasing the chance that a patient has a healthy embryo from a cycle. Many patients end up having more embryos then they need in their initial treatment, and these embryos are frozen for the patient to use in a future pregnancy attempt.

In cycles where the patient is testing the genetic health of an embryo before transferring it for pregnancy, embryologists will biopsy one or more embryos to screen for chromosome and genetic abnormalities that may result in miscarriages or severely debilitating or even fatal birth defects, such as Tay-Sachs disease and Edwards syndrome. Most Tay Sachs babies die by age 5; 90% to 95% of Edwards syndrome infants surviving miscarriage do not live to their first birthday. Today, genetic testing of IVF-created embryos – known as pre-implantation genetic (PGT) testing – can detect hundreds of genetic and chromosomal abnormalities. Because embryologists can biopsy embryos in the lab much earlier than can occur in spontaneous pregnancies, IVF can decrease the chance that expectant mothers face the heartbreak of discovering life threatening syndromes in pregnancy, often when pregnancy termination for fatal syndromes is not an option, except to save the life of the mother.

Now that you understand the basics of early embryo growth and IVF, lets dive further into why a personhood law can affect IVF care, as well as many other aspects of life.

• As of March 1, 2025, more than two-dozen states, including Tennessee, had introduced so-called personhood laws that would define life as beginning at conception (defined as the moment a sperm enters the egg), thereby considering fertilized eggs in a lab or in a human  as human beings. Why does this matter? Consider the impact this has on an IVF lab: All embryos in frozen storage, including those cryopreserved for as long as a quarter-century, may be required to remain there indefinitely, as it would likely be illegal to discard an embryo if it is now considered a human being.
• In states with personhood laws, neither the parents nor their IVF clinics (with parental permission) could destroy the embryos without risk of criminal prosecution.
• Parents also could not donate unused embryos – even those with significant defects rendering them incapable of producing healthy pregnancies – for life-saving research into Parkinson’s disease, Alzheimer’s disease, Multiple sclerosis and Amyotrophic lateral sclerosis (Lou Gehrig’s disease), nor could they be donated for FDA-approved stem-cell therapy for leukemia, lymphoma multiple myeloma (bone marrow cancer) and neuroblastoma (a cancer affecting the nervous system of children).
• Forcing people to keep embryos in storage forever is costly, ranging from around $600-1000 annually. If patients abandon their embryos, clinics are left financially and legally responsible for the cost to keep embryos in storage, even though the patients no longer want them to be stored.
• IVF clinics have countless protocols in place to take superb care of embryos – but despite best efforts, sometimes embryos don’t survive a procedure (most commonly not surviving an embryo thaw). Would patients or the state hold a clinic responsible for involuntary manslaughter if an embryo didn’t survive a thaw procedure? If so – IVF would stop (like it did temporarily in Alabama back in 2024) when a court temporarily granted embryos personhood rights. Clinics would not be willing to take on the potential criminal risks of involuntary manslaughter when working with embryos.

Beyond IVF – think about the other potential implications if we grant personhood rights to a fertilized egg or a fetus:

• Does the patient get to claim a child tax credit when she’s pregnant?
• Can she start a 529 savings program when she gets a positive pregnancy test?
• Is she eligible to use the HOV lane on the highway? It sounds ridiculous, but if we’re granting personhood status to an embryo, technically, there are 2 people riding in a car when a pregnant woman is driving.
• If the woman has a miscarriage, through no fault of her own, could someone try to prosecute her for involuntary manslaughter if they thought she wasn’t doing enough to take care of herself when she was pregnant?
• What happens if both parents die without a will – would the embryos become the beneficiaries of the estate with equal rights to surviving children? Would they be forced to be transferred to a gestational carrier to produce a potential pregnancy, since they’re being given the rights of a human, even though the parents are dead? Imagine a scenario where a human is forced to be born as an orphan.

It sounds extreme – but classifying a fertilized egg as a person starts a slippery slope of many implications for the woman, her family and her health care team. Why does this matter to you if you’re considering IVF?

Because your elected leaders need to hear from you – and need to know that you want to make your health care decisions with your health care provider, not with laws in place restricting your ability to make personal decisions about your health care and your embryos.

Embryos deserve deep respect, they offer the potential of a new human life. But they are not in fact human when they are undifferentiated cells. We urge patients to reach out and share their story and with their elected leaders, find yours here. Speaking out helps them understand the real-life implications that passing these laws mean in terms of restricting your ability to build a family.