The virus had not breached them, despite active infection.
Nove meses após o início da pandemia, pesquisadores de uma clínica de fertilidade espanhola trouxeram uma descoberta que, sem resolver o mistério da transmissão vertical do coronavírus, ao menos ilumina um de seus caminhos: o vírus parece incapaz de penetrar nos óvulos humanos. O estudo, pequeno mas cuidadoso, sugere que a fertilização in vitro pode ser um procedimento seguro mesmo para mulheres infectadas — e lembra que a ciência avança não apenas pelas certezas que acumula, mas pelas dúvidas que aprende a nomear.
- Bebês nascendo com COVID-19 de mães infectadas criaram uma urgência científica: por onde, exatamente, o vírus atravessa para a nova vida?
- Dois óvulos coletados de doadoras positivas para SARS-CoV-2 não apresentaram RNA viral — uma ausência que desafia a lógica, já que os receptores necessários para a infecção estavam presentes nas células.
- A descoberta abre espaço para que procedimentos de reprodução assistida sejam considerados seguros mesmo durante infecção ativa, aliviando uma tensão clínica real para médicos e pacientes.
- Especialistas alertam: a transmissão vertical por outras vias — como a placenta — ainda não está descartada, e uma infecção grave durante a gestação continua sendo um risco independente.
- O estudo é um passo, não uma resposta — e seus próprios autores pedem cautela antes que qualquer conclusão definitiva seja tirada.
Nove meses após o início da pandemia, uma pergunta persistia: como alguns bebês nasciam com COVID-19 se a transmissão pelo material reprodutivo parecia improvável? Um estudo publicado no final de setembro trouxe uma resposta parcialmente tranquilizadora — ao menos no que diz respeito aos óvulos humanos.
A pesquisa partiu de uma clínica de fertilidade espanhola do Grupo Eugin. Duas mulheres que doavam óvulos chegaram para a coleta no final de fevereiro e, contrariando o protocolo da época — que só testava pacientes com sintomas evidentes —, foram submetidas ao teste PCR. Dois dias depois, ambas deram positivo para SARS-CoV-2. Uma havia tido sintomas leves semanas antes; a outra era assintomática.
Ao analisar os óvulos congelados, os médicos não encontraram RNA viral em nenhum deles. A ausência foi considerada significativa: o coronavírus depende de receptores específicos, como ACE2 e basigina, para invadir células — e esses receptores estavam presentes nos óvulos. Ainda assim, nenhum fragmento viral foi detectado. O gene N do vírus, marcador central de sua estrutura, simplesmente não estava lá.
Edardo Motta, do Grupo Huntington, explicou que a ausência de replicação viral nos óvulos sugere que o vírus não consegue se instalar nessas células. Biologicamente, isso faz algum sentido: os óvulos se formam ainda na vida fetal e permanecem em estado de baixa atividade, ao contrário dos espermatozoides, produzidos continuamente — e nos quais o vírus parece ter maior facilidade de atuação.
As implicações clínicas são promissoras, mas os próprios pesquisadores pedem cautela. A transmissão vertical por outras rotas, como a placenta, ainda está sendo investigada, e casos raros de contágio intrauterino já foram documentados. Além disso, mesmo que o vírus não infecte os óvulos, uma COVID-19 grave durante a gestação pode trazer riscos sérios ao feto e provocar parto prematuro. O estudo abre uma janela importante — mas muitas outras precisam ser abertas antes que o quadro completo possa ser visto.
Nine months into the pandemic, a question still lingered: how were some babies born with COVID-19 when their mothers carried the virus? A study published in late September offered a reassuring answer—at least for one potential transmission route. Researchers found no evidence that the coronavirus could penetrate human egg cells, suggesting that vertical transmission through reproductive material might not be possible and that in vitro fertilization could remain safe even for women infected with the virus.
The research came from a Spanish fertility clinic and involved two women who had undergone controlled ovarian stimulation to donate their eggs. When they arrived at the clinic in late February to have their oocytes collected, both tested positive for SARS-CoV-2 by PCR. One woman had experienced mild flu-like symptoms earlier that month; the other showed no respiratory signs in the weeks before collection. At the time, Spain's testing protocol only screened people with obvious COVID-19 symptoms, so neither had been tested initially. On collection day, the medical team decided to test the donors anyway. Two days later, both results came back positive.
Curious whether the virus had infiltrated the reproductive cells, doctors from the Eugin Group analyzed the frozen eggs afterward. They found no viral RNA inside them. The absence was striking because the virus requires specific molecular machinery to infect cells—receptors like ACE2 and basigin that sit on the surface of most cells in the female reproductive tract, including the ovaries and uterus. Other coronaviruses, including SARS and MERS, use these same proteins to enter cells. Yet despite the presence of these receptors on the egg cells, and despite the women's active infection, the virus had not breached them.
Edardo Motta, director of the Huntington Group, explained the finding in technical terms: researchers looked for the viral N gene, a protein the coronavirus produces as part of its core structure. It was absent. They also checked whether the viral entry receptors showed signs of viral fragments occupying them. They did not. Everything that should have indicated viral penetration into the cells was simply not there. This mattered because it suggested the virus could not replicate inside the eggs—a requirement for actual infection.
The question of how some newborns contract COVID-19 remains open. Most babies born to infected mothers test negative, but a small number have tested positive, prompting scientists to investigate whether transmission occurs across the placenta. David Schwartz, a specialist in placental pathology, has been studying this question and noted that recent research suggests rare cases of transplacental transmission are occurring. Paulo Gallo, an assisted reproduction specialist, acknowledged that vertical transmission of other viruses—zika, HIV, hepatitis—is well established and can happen during pregnancy, delivery, or breastfeeding. But for COVID-19, he emphasized, there is no confirmed evidence of transmission through egg cells, whether through assisted reproduction or natural conception.
The implications were significant but cautious. If the virus cannot infect egg cells, then in vitro fertilization might be a safe procedure even for women with active COVID-19 infections, and laboratory handling of reproductive material from infected donors would not pose a risk to healthcare workers. Motta noted an intriguing biological difference: egg cells form during fetal development and remain largely inactive, whereas sperm are continuously produced throughout a man's life. Interestingly, the coronavirus appears to show more robust activity in testicular tissue than in ovarian tissue, suggesting the virus may have an easier time replicating in actively producing reproductive cells.
Yet the researchers themselves urged restraint. They acknowledged they could not exclude other pathways through which the virus might infect egg cells. Motta emphasized that the findings should not be treated as reassurance that pregnant women could relax their guard. Even if vertical transmission through eggs proves unlikely, a severe COVID-19 infection during pregnancy could still pose risks to the fetus and trigger premature labor. Women becoming pregnant during the pandemic, he stressed, must continue protecting themselves. The study opened a door to understanding how the virus moves through the body, but many more studies would be needed before anyone could confidently say they had found all the answers.
Notable Quotes
If the virus cannot infect egg cells, then in vitro fertilization might be a safe procedure even for women with active COVID-19 infections— Eduardo Motta, director of the Huntington Group
For COVID-19, there is no confirmed evidence of transmission through egg cells, whether through assisted reproduction or natural conception— Paulo Gallo, assisted reproduction specialist
The Hearth Conversation Another angle on the story
Why does it matter whether the virus can get into egg cells specifically? Couldn't it just infect the baby some other way?
It matters because if the virus could penetrate eggs, it would mean infected women couldn't safely donate eggs or do IVF—the virus could be passed directly into the genetic material. But more fundamentally, it's one of the few ways we can actually trace how transmission happens. Most babies born to infected mothers are fine, but some aren't, so we need to map every possible route.
The study looked at two women. That seems like a very small sample. How confident should we be in this?
Very cautiously. The researchers themselves said so. Two cases is enough to raise a hypothesis—the virus wasn't in those eggs—but it's not enough to declare the route impossible. What matters is that they found a mechanism: the virus needs specific receptors to enter cells, and those receptors weren't being used by viral fragments. That's testable. That's reproducible.
You mentioned the virus acts differently in men's reproductive tissue. Why would that be?
Eggs are formed before birth and then sit dormant for years. Sperm are made fresh constantly, throughout a man's life. The virus seems to prefer active, replicating cells. A dormant egg cell is a harder target than a factory constantly churning out new sperm.
So if IVF is safe for infected women, does that mean they should go ahead and do it?
Not yet. Safe in the lab is different from safe for pregnancy. A woman with severe COVID-19 can still have a rough pregnancy, premature labor, complications. The egg cells might be protected, but the woman carrying them might not be.
What's the next question scientists need to answer?
Whether the virus crosses the placenta. That's where the real mystery is. Some babies are being born infected, and the placenta is the most likely culprit. Until we understand that, we won't have the full picture.