Two women can already have a biological child together using assisted reproduction, and emerging science is pushing toward methods that would let both partners contribute genetically in ways that go far beyond what clinics offer today. Right now, a technique called shared IVF allows one woman to provide the egg and the other to carry the pregnancy, giving each a distinct biological role. In research labs, scientists have gone further: they have produced healthy mice from two mothers with no paternal DNA at all. Translating that work to humans is still years away, but the trajectory of the science is real and accelerating.
Shared IVF and the ROPA Method
The most established way for two women to have a baby together is called the ROPA method, short for Reception of Oocytes from PArtner. One partner provides the eggs (making her the genetic mother), the eggs are fertilized with donor sperm through standard IVF, and the resulting embryo is transferred to the other partner, who carries the pregnancy and gives birth (making her the gestational mother).1PubMed Central. Lesbian shared IVF: the ROPA method: a systematic review Donor sperm is still required, so both women don’t contribute equally at the genetic level. But the method gives each partner a concrete biological connection to the child, which matters to many couples.
A reasonable concern is whether the absence of a genetic link between the embryo and the woman carrying it affects outcomes. Research comparing ROPA cycles to conventional IVF, where the same woman provides the egg and carries the pregnancy, has found similar reproductive results between the two.2PubMed Central. Similar reproductive outcomes between lesbian-shared IVF (ROPA) and IVF with autologous oocytes That finding makes physiological sense: egg donation IVF has been used successfully for decades, and the uterus does not require a genetic match to the embryo for implantation and healthy development.
From the child’s perspective, studies looking at mother-child relationships in families formed through shared biological motherhood have been reassuring. Researchers found no differences in bonding quality between these families and those formed through standard donor IVF. Both birth mothers and non-birth mothers showed high levels of warmth, competence, and confidence in their parenting, with low levels of anger or disappointment.3Oxford Academic. Relationships between mothers and children in families formed by shared biological motherhood Within shared-motherhood families, gestational mothers and genetic mothers did not differ from each other in the quality of their bond with the child either.
Why Two Eggs Alone Cannot Make a Baby
If shared IVF still requires donor sperm, you might wonder why scientists can’t just combine the DNA from two eggs. The short answer is genomic imprinting. Mammals have evolved a system in which certain genes work differently depending on whether they came from the mother or the father. Some genes are active only when inherited from the father and silenced when inherited from the mother, and vice versa. This means a mammalian embryo needs one set of instructions that has been “stamped” by a male body and one that has been stamped by a female body.
A well-studied example involves two neighboring genes. One is a growth factor that is expressed only from the copy inherited from the father, while the other is a non-coding gene transcribed only from the maternal copy.4PubMed Central. Epigenetic regulation of the Igf2/H19 gene cluster If an embryo received two maternal copies, it would get a double dose of the maternal gene and zero of the paternal growth factor. Multiply that conflict across dozens of imprinted regions scattered throughout the genome and you get an embryo that simply cannot develop normally. This is the core barrier to two-mother reproduction without sperm, and it is the wall that laboratory researchers have been chipping away at.
Bimaternal Mice and Editing the Imprint
In 2018, a team in China achieved something that had seemed like a biological impossibility: they produced healthy, fertile mice from two mothers and no father. The researchers started with a special kind of stem cell that carries only half the normal number of chromosomes, similar to an egg. They then used gene-editing tools to delete three imprinted regions that would normally cause problems in a two-mother embryo. Those edited stem cells were injected into normal eggs from a second female mouse. Out of 210 embryos transferred, 29 live mice were born, roughly a 14 percent success rate, comparable to standard assisted reproduction in mice. The pups had normal body and placenta weights, normal behavior, and grew up to be fertile adults. When researchers checked the full set of imprinted genes, every one was being expressed correctly.5Cell Stem Cell. Generation of Normal Bimaternal and Bipaternal Mice from Hypomethylated Haploid ESCs with Imprinted Region Deletions
More recently, researchers have taken a different tack. Rather than permanently deleting imprinted regions from the DNA sequence, they used CRISPR-based tools to change only the chemical tags on the DNA, the epigenetic marks that tell a gene whether to be active or silent. By editing the methylation patterns at seven imprinting control regions, a team produced what they called “androgenetic” mice, animals born from two fathers’ genomes with the maternal imprint artificially installed.6PubMed Central. Fertile androgenetic mice generated by targeted epigenetic editing of imprinting control regions The principle works both ways: the same epigenome-editing approach could theoretically be used to stamp a maternal genome with the paternal pattern, enabling two-mother reproduction without any gene deletions at all.
Targeted epigenome editing at individual imprinted loci has been shown to ripple across an entire imprinted domain, affecting gene expression and histone modifications far beyond the editing site.7Nucleic Acids Research. Epigenome editing reveals core DNA methylation for imprinting control in the Dlk1-Dio3 imprinted domain That finding is both powerful and sobering. It means a single well-placed edit can fix an entire cluster of genes, but it also means an imprecise edit could cause cascading problems. High-throughput screens of the regulatory regions at specific imprinted loci are now revealing exactly which DNA elements control the maintenance of imprinting, mapping the targets that would need to be hit in any future human application.8Cell Genomics. High-throughput epigenome editing screens reveal therapeutic regulatory elements of the Prader-Willi syndrome locus
In Vitro Gametogenesis and Making Eggs from Skin Cells
Even if imprinting could be solved, there is a second hurdle: you need an egg and something that functions like a sperm to create an embryo. For two women, the egg supply is straightforward. But creating a functional sperm-like cell from a woman’s body is a much harder problem. This is where in vitro gametogenesis, or IVG, comes in. IVG refers to the process of coaxing ordinary body cells (like skin or blood cells) into becoming functional eggs or sperm in a lab dish.
The concept received dramatic proof in mice when researchers took skin cells from a male mouse, reprogrammed them into stem cells, grew them until some spontaneously lost their Y chromosome, and then drove those stem cells to become egg cells. Those lab-made eggs were fertilized with normal sperm and transferred to a surrogate, resulting in live mouse pups, mice with two genetic fathers.9PubMed Central. Pluripotent Stem Cell-Derived In Vitro Gametogenesis and Synthetic Embryos—It Is Never Too Early for an Ethical Debate For two women, the reverse would be needed: taking a female cell and steering it toward becoming something functionally equivalent to sperm. Researchers have been candid that deriving sperm from female cells, or eggs from male cells, is believed to be particularly difficult and may prove harder than the reverse.10BMJ Journals. Using stem cell-derived gametes for same-sex reproduction: an alternative scenario
Creating artificial human oocytes from patients’ body cells has been attempted since the early 2000s, typically by transferring a patient’s cell nucleus into a donor egg that has had its own nucleus removed. The fundamental challenge is that you need to accomplish two things at once: reduce the DNA from a full set to a half set (as a natural egg or sperm would have), and reprogram that DNA so it can support all stages of embryonic development.11PubMed Central. Human artificial oocytes from patients’ somatic cells: past, present and future Those two requirements sometimes work against each other, and no lab has yet produced a fully functional human egg from a body cell.
How Far Away Is This for Humans
Mouse success stories are exciting, but the gap between mice and humans in reproductive biology is wide. Mouse embryos develop much faster, mouse imprinting patterns don’t perfectly mirror human ones, and the ethical constraints on experimentation are fundamentally different. Researchers can produce hundreds of mouse embryos, implant them in surrogates, and study the offspring over multiple generations. None of that is permissible or practical in humans.
The 2018 bimaternal mouse experiment required deleting three imprinted regions, and even then the success rate was about one in seven. Applying that approach to humans would mean permanently altering the genome of a future child, something that falls far outside the current ethical and legal framework for reproductive medicine in virtually every country. The epigenome-editing approach is more appealing precisely because it does not change the DNA sequence itself, only the chemical tags that govern gene expression. But whether epigenome edits remain stable across human development, through decades of cell division and tissue specialization, is unknown.
IVG faces its own translation hurdles. The mammalian gametogenesis pathway involves dozens of precisely timed steps, many of which are guided by signals from surrounding body tissues that are difficult to replicate in a dish. The scientific consensus is that clinical use of IVG-derived gametes for human reproduction will require extensive ethical and legal deliberation before it even approaches a clinic.12PubMed. Mammalian in vitro gametogenesis We are likely talking about decades, not years, before any of these laboratory techniques produce a human baby.
What the Gestational Partner Actually Contributes
A common misconception about shared IVF, and about egg-donor pregnancies in general, is that the gestational mother is merely a “carrier” with no biological influence on the child. In reality, the uterine environment actively shapes embryonic development. Small RNA molecules produced by the lining of the uterus communicate with the embryo during implantation, influencing which genes are activated in the early stages of development. Disruptions in this molecular dialogue are linked to implantation failure and pregnancy complications.13Reproductive and Developmental Medicine. Role of microRNAs in embryo–endometrial interactions: biological functions and clinical applications
Beyond these molecular signals, the gestational mother’s diet, stress levels, immune environment, and hormonal profile all influence fetal gene expression through epigenetic mechanisms. A child carried by a gestational mother is shaped by that pregnancy in ways that go beyond the DNA in the fertilized egg. For couples using the ROPA method, this means both partners leave a biological mark on the child: one through her genome and the other through the gestational environment.
Mitochondrial DNA Adds Another Layer
There is a third biological contribution that is sometimes overlooked. Mitochondria, the energy-producing structures inside every cell, carry their own small genome that is inherited exclusively from the egg. In standard ROPA, the mitochondrial DNA comes from the genetic mother who provided the egg, not from the gestational mother. But mitochondrial replacement techniques, originally developed to prevent mothers from passing mitochondrial diseases to their children, open an unusual possibility. In these procedures, the nucleus from one woman’s egg is transferred into a donor egg whose own nucleus has been removed, resulting in an egg that carries one woman’s nuclear DNA and another woman’s mitochondrial DNA. The replacement can be done with very high efficiency, with the resulting embryos containing over 99 percent donor mitochondrial DNA.14Nature. Mitochondrial replacement in human oocytes carrying pathogenic mitochondrial DNA mutations
In theory, combining ROPA with mitochondrial replacement could produce a child with nuclear DNA from one woman (via the egg), mitochondrial DNA from the other woman (via the enucleated egg shell), and gestation by either partner. This is not currently practiced for same-sex couples, and mitochondrial replacement is legally restricted to preventing disease in most jurisdictions that allow it at all. But biologically, the pieces exist.
The Ethics of Emerging Reproductive Technologies
The ethical discussion around these technologies is already well underway, and it does not break down as simply as supporters versus opponents. Ethicists have argued that the principles of reproductive justice and beneficence generate strong reasons to support the development of IVG for same-sex reproduction, treating it similarly to how society treats opposite-sex assisted reproduction.15Bioethics. Drawing the line on in vitro gametogenesis The argument is that if we accept IVF, egg donation, and surrogacy as legitimate ways to help heterosexual couples build families, the same principles should extend to technologies that serve same-sex couples.
Where most ethicists draw a harder line is on solo reproduction, the idea that a single person might use IVG to create both egg and sperm from their own cells, becoming both genetic parents of a child. That scenario raises distinct concerns about genetic diversity and the welfare of the resulting child, and it does not carry the same reproductive-justice rationale. The key concern with any of these technologies, though, is safety. Epigenome editing and IVG both carry risks of subtle errors that might not manifest until years or even generations later. Proceeding cautiously is not squeamishness; it is basic child welfare.
Access and Cost Barriers
Even the technologies that exist today are out of reach for many couples. IVF is expensive, typically running into the tens of thousands of dollars per cycle in the United States, and insurers have long treated infertility as a socially constructed condition, making IVF an elective intervention that many plans do not cover.16PubMed Central. Impact of in vitro fertilization state mandates for third party insurance coverage in the United States: a review and critical assessment Fewer than a quarter of infertile couples have sufficient access to fertility care in the US. For same-sex female couples, access is often even more constrained, because many state insurance mandates define infertility in terms that assume a male partner and require documented failure to conceive through intercourse.
ROPA adds the cost of coordinating two cycles: one for egg retrieval from the genetic mother and one for embryo transfer to the gestational mother, plus donor sperm. In countries where the ROPA method is legal and regulated, such as Spain and parts of the UK, public health systems sometimes cover a portion of the cost. In others, same-sex couples face both legal restrictions and financial barriers. Any future technologies like IVG or epigenome editing would initially be research-grade procedures, priced accordingly, and available only at a handful of academic medical centers. The history of reproductive technology suggests that costs come down over time, but “over time” can mean decades.
Parthenogenesis in Nature
It is worth noting that female-only reproduction does occur naturally in some animals, though not in mammals. Parthenogenesis, the development of an embryo from an egg without any sperm, has been documented across vertebrate groups. It occurs regularly in certain lizard and snake species and has been observed in isolated cases in birds, fish, and sharks.17PubMed. Facultative Parthenogenesis in Vertebrates: Reproductive Error or Chance? In these cases, the egg essentially provides both halves of the genome, sometimes by duplicating its own chromosomes.
Mammals cannot do this naturally because of the imprinting system described earlier. The evolutionary reason for imprinting is debated, but the leading theory involves a genetic tug-of-war between maternal and paternal interests. Paternally expressed genes tend to push for larger, more resource-hungry offspring, while maternally expressed genes tend to restrain growth to protect the mother. This conflict only arises in species where mothers invest heavily in pregnancy and nursing, which is exactly the situation in mammals. It is, in a sense, the evolutionary legacy of mammalian pregnancy that makes two-mother reproduction so difficult, and solving it requires outsmarting millions of years of evolutionary wiring.
The Legacy of Cloning Science
Much of the foundational knowledge enabling these advances traces back to cloning research. The birth of Dolly the sheep in 1996 demonstrated that a nucleus from an adult cell could be reprogrammed to support full embryonic development when placed inside an egg cell stripped of its own nucleus.18PubMed Central. Somatic cell nuclear transfer: origins, the present position and future opportunities That experiment’s most lasting impact was not cloning itself but the insight that eggs contain unknown factors capable of resetting a cell’s developmental clock. If an egg could reprogram an adult nucleus, scientists reasoned, there must be other ways to achieve the same reset. That line of thinking led directly to the development of induced pluripotent stem cells and, eventually, to the IVG research that now underpins hopes for same-sex genetic parenthood.
The reproductive technologies available to two women today, from shared IVF to the research pipelines exploring IVG and epigenome editing, form a continuum. At one end sits a technique you can access at a fertility clinic this year. At the other end sit mouse experiments whose human applications remain speculative. What connects them is a steady expansion of what biology allows and what society chooses to support, driven by the same question couples have always asked: how do we have a child that is ours?