Repronews #61: 400 million reprotech babies by 2100?
Uncertainties of polygenic editing; reprotech vs fertility decline; Denmark's generous IVF system; study: housing credit for 20-25 year-olds increases childrearing 33%

Welcome to the latest issue of Repronews! Highlights from this week’s edition:
Repro/genetics
A paper in Nature argues that heritable polygenic editing for health remains “unsafe and unproven”
Population Policies & Trends
A 2018 study found that reprotech could enable an extra 157 to 394 million to be alive in the world in 2100
Professor Roger Gosden argues that public funding for reprotech can “soft the landing” of declining fertility across the world
Professor Claus Yding Andersen explains how Denmark’s public provision of IVF has increased fertility, now contributing 8-10% of all babies
Brazilian study finds housing credit lotteries increased number of children among 20-25 year-olds by 33%
Genetic Studies
Further Learning
Repro/genetics
“Embryo editing for disease is unsafe and unproven” (Nature)
Shai Carmi, Kevin Mitchell, and Hank Greely argue the supposed potential benefits of heritable polygenic editing are highly uncertain, while significant risks remain.
Reacting to a study estimating significant health benefits of polygenic editing for preventing diseases, the authors write: “mathematical models are only as good as the assumptions they are based on.”
The authors fault the study for assuming:
Perfect accuracy of gene editing.
Accurate identification of genetic variants that have causal effect, whereas “studies do not identify causal alleles, but only common genetic variants that are linked with the variants that cause the disease or trait. Mapping causal variants has been a slow process so far, and for many traits, even some of the most well-investigated ones, there is contradicting evidence about the causal genetic mechanism.”
That the protective effects of different variants are independent and will add up, whereas there may be dependence, interaction, or redundancy between variants.
That alleles that are protective in one environment today might not be protective in other environments, today or in the future.
That the degree of risk reduction would be the same across the relevant population, but it would inevitably vary.
In addition, even precise polygenic editing could have negative unforeseen side effects due to new genetic interactions.
The authors conclude that “heritable editing might well be worth exploring in non-human animal models, to test whether the underlying assumptions hold in real life” but argue that focusing on human editing would distract from more relevant and imminent reproductive technologies.
More on repro/genetics:
Southern African Society for Human Genetics (SAHG) has called for changes to research guidelines to explicitly prohibit heritable human gene editing (Nature)
“ARCUS: An advanced gene editing tool appears to have cured an infant of an early onset metabolic disorder” (GLP/Science)
Population Policies & Trends

“A demographic projection of the contribution of assisted reproductive technologies to world population growth” (RBMO)
The authors of this 2018 study provide estimates for the number of people conceived with reproductive technology by 2100.
“Since the first IVF baby in 1978, the number of people conceived by reproductive technology has grown much faster than expected, reaching several million today and rapidly approaching 0.1% of the total world population.”
“The chief variable driving growth is access to fertility services. If it stagnates at current levels of about 400,000 babies per year, an estimated 157 million people alive at the end of the century will owe their lives to assisted reproductive technologies (1.4% of global population).”
If fertility services are expanded to enable the number of assisted births to increase by 30,000 annually there would be 394 million resulting people alive by 2100 (3.5% of global population).
“As the conquest of infertility continues, individuals who owe their lives to assisted reproductive technologies will quietly make a significant contribution to demographic growth as well as social progress.”
“Fertility treatment for the demographic transition” (Roger Gosden)
Professor Roger Gosden argues that assisted reproductive technologies (ARTs) can “soften the landing” of declining fertility across the world.
While the impact of pronatalist economic incentives are unclear, supporting access to IVF ensures more babies are born.
“While many people choose smaller families or stay childless, millions of others worldwide cannot have children,” Gosden argues. “They don’t have access to fertility services and can’t afford them. A national investment can pay off demographically while fulfilling the hopes of people committed to parenting given the chance and able to raise fine citizens. Isn’t this a win-win?”
“We never make a finer investment than in our children. And yet, infertility was a Cinderella subject for far too long and denied much public funding or even sympathy. The subspecialty is now mature but remains short-changed for research into improving treatment and bringing down costs.”
Gosden argues: “The translation of a generous policy beyond other welfare states may seem unlikely, but where humanitarian sympathy for involuntary childlessness is not enough, perhaps a national self-interest in boosting the numbers of youth will prevail.”
“Denmark’s investment in fertility treatment to normalize demography” (Roger Gosden)
Professor Claus Yding Andersen writes on Denmark’s generous and effective system of coverage for fertility treatments.
Denmark pays most of the cost of most people needing treatment with assisted reproduction technologies (ARTs), providing high-quality public sector services.
Infertility is the most common reason for 20 to 40-year-old Danes to seek medical care. Women up to age 40 can benefit from free ART whether or not they have a male partner or are lesbians.
As of January 2025, women are entitled a number of stimulation cycles with IVF for the carrying to term of up to 2 children.
Doctors are not allowed to offer these public services to persons they believe will not make good parents.
Private fertility clinics thrive in Denmark in addition to public services, offering treatment to women up to age 45.
Denmark has one of the highest ART birth rates, with assisted conception enabling 8-10% of all babies. That’s about two children in every school classroom.
Professor Andersen writes: “Each country seeks its own path to raise birthrates, and no single policy is likely to be a panacea. Denmark’s direct approach guarantees more babies. It offers a generous and equitable allowance of ART and bridges financial barriers for people who qualify but cannot afford private care. Helping people overcome infertility is an obvious strategy for tackling the demographic problem.”
He suggests more public research funding could enable breakthroughs to further improve ART “so more people can share the joy of family building that carries a social dividend.”
“Housing and fertility” (SSRN)
This study examines the impact of access to housing on fertility rates using random variation from housing credit lotteries in Brazil.
The authors found that obtaining housing among 20-25 year-olds increased the average chance of having a child by 32% and the number of children by 33%
There was no increase in fertility for people above age 40.
Thelifetime fertility increase for a 20-year old is twice as large from obtaining housing immediately relative to obtaining it at age 30.
The increase in fertility was stronger for households in areas with lower quality housing, greater rental expenses relative to income, and those with lower household income and lower female income share.
The authors conclude that alleviating housing credit and physical space constraints may significantly increase fertility.
More on population policies and trends:
“Human reproduction as prisoner’s dilemma: The decline of marriage in the West” (Aporia)
Genetic Studies
“Genetic link to recurrent miscarriage identified” (PET)
“Rare genetic condition where patients can never sleep again” (Geo News)
“Rare genetic disease appears to be cured after gene therapy” (PET)
“Why new precision oncology treatments benefit patients of some ancestries more than others” (Medical Xpress)
Further Learning
More on human nature, evolution, and biotech:
Podcast: “Is hereditarian research ‘abhorrent’?” (Aporia)
“Early humans are one of the few animals that did not migrate when the climate cooled” (GLP)
“Disease-resistant, gene-edited pork may go on sale in the US in 2025” (BGR)
Report: Biopower: Security American Leadership in Biotechnology (CNAS)
The U.S. Department of Commerce is imposing new export controls on biotech equipment and related technology to China due to national security concerns (Medical Buyer)
“MAHA v. Big Food: Will a left-MAGA coalition crystallize to fundamentally change the US food system?” (GLP)
Disclaimer: We cannot fact-check the linked-to stories and studies, nor do the views expressed necessarily reflect our own.