There are lockdown babies conceived, gestated, and born entirely while the world was struggling with the COVID-19 pandemic who are now over a year old. That means we’re entering the point where we can answer a question that’s been on many people’s minds: what effect, if any, does COVID-19 have on developing fetuses?

A preliminary analysis of 212 pregnancies in facilities across Spain has revealed some concerning results. “We found that certain elements of the NBAS [Neonatal Behavioral Assessment Scale] measurement were changed in six-week-old infants who had been exposed to the SARS-COV-2 virus,” said researcher Águeda Castro Quintas, who is set to present the results at the European Congress of Psychiatry this Tuesday, in a statement.

“Effectively they react slightly differently to being held, or cuddled,” she explained.

There’s not much (outside of pooping, crying, and sleeping) that we tend to expect from six-week-old babies, but this early stage of life is an important period of growth and development for new humans. Your standard-issue baby can likely smile by this age – out of happiness, not because they need to toot – and can recognize their carers’ voices out of a crowd.

However, another area being silently toiled away on during these first weeks is motor function, which is control over movement. It may not seem impressive from an adult perspective, but gripping onto a rattle and giving it a shake (and not dropping it!) is a really big achievement when you’re less than two months old. So too is lifting and moving your head and shoulders – but this is another area that seems to be targeted by a maternal COVID-19 infection.

“Each mother and baby was closely examined by clinicians with expert training in the field and in the tests,” said Castro Quintas. “We found that babies whose mothers had been exposed to COVID did show neurological effects at 6 weeks, but we don’t know if these effects will result in any longer-term issues.”

Of course, with such a small sample and only the first six weeks measured, the team caution against drawing too strong a conclusion from the results. “Not all babies born to mothers infected with COVID show neurodevelopmental differences,” said Rosa Ayesa Arriola, lead researcher on the project.

“But our data shows that their risk is increased in comparison to those not exposed to COVID in the womb,” she explained. “We need a bigger study to confirm the exact extent of the difference”.

This isn’t the first study to hint that COVID-19 infection during pregnancy may have some adverse effects on offspring. The results are “in line with similar research from Mexico published in PlosONE in May 2022 … [and] a Chinese study published in Frontiers in Paediatrics in December 2021,” Mariya Hristova, Principal Research Fellow at the Institute for Women's Health, UCL, who was not involved in the study, explained to IFLScience.

Both studies point to a link between COVID-19 infection in pregnancy and adverse effects on neurological development, Hristova said, with babies showing “lower levels in communication, gross movement, fine movement, problem solving, and personal-social domains … [and] an increased risk of development of neurological disorders.”

Add those to the “devastating” risks previously discovered by researchers studying the impacts of COVID-19 infection in pregnancy, such as low birth weight and stillbirth, and it seems it can have some pretty severe consequences. This in fact raises further questions, since “[unlike] other viruses … SARS-CoV-2 does not cross the placenta,” Hristova told IFLScience.

There are plenty of other viruses, like Zika or cytomegalovirus, which can cause neurological problems for newborns if contracted in pregnancy. However, these viruses have such a profound effect on fetal development because they can cross not just the placenta, but the blood-brain barrier, Hristova explained, meaning they can affect the infant’s brain development directly.

COVID-19 is different – it can’t do that. Yet we have multiple studies now showing that COVID-19 infection during pregnancy has some effect on babies’ brain development. So what gives?

“The mechanism behind the effect of maternal SARS-CoV-2 infection on the neonatal brain development is unclear … [but it] could be through the cytokine surge reported in SARS-CoV-2 patients,” Hristova told IFLScience. She’s referring to one of the more darkly ironic side effects of COVID-19: the tendency for some people’s bodies to massively overreact to the infection, causing hyper-inflammation and potentially long-term autoimmune conditions.

“Although [the cytokine surge is] triggered in the infected pregnant mother without directly challenging the fetus, [it] causes an immune response in the fetus and makes it more susceptible to challenges, which can impose risk to neurodevelopment,” Hristova explained.

“A similar mechanism underlies the adverse effect of intrauterine maternal infection on infants’ neurodevelopment,” she told IFLScience. “The fetal brain, although not directly affected by the infection, becomes highly susceptible to low oxygen conditions and subsequently brain damage.”

Whatever the reason for the effect, the team behind the new results is clear that further research is needed – not only to bolster sample numbers, but to figure out the longer-term consequences on neonatal development.

“This is the right moment to establish international collaborations that would permit us to assess long-term neurodevelopment in children born during the COVID-19 pandemic,” added Ayesa Arriola. “Research in this field is vital in understanding and preventing possible neurological problems and mental health vulnerabilities in those children in the coming years”.