Experts say children’s early years of life are their most formative — their brains soak up every interaction and experience, positive and negative, to build the neural connections that will serve them for the rest of their lives.

For the cohort of “lockdown babies,” the “first year of life was very different to the pre-pandemic babies,” Susan Byrne, a pediatric neurologist at the Royal College of Surgeons in Ireland and lead author of the study, told The Washington Post.

But she and the other authors of the study have one message for parents: Don’t be too worried. “Babies are resilient and inquisitive by nature,” they note, and are likely to bounce back given the right support.

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While the pandemic is not over, and experts say it could be years before they have a fuller picture of its effects on children, parents around the world have already begun to report noticing differences in their lockdown babies.

When Chi Lam, 33, had her first child, Adriana, in April 2020, England was in lockdown. Most people were not permitted to leave their homes without a “reasonable excuse.” Her parents and in-laws, who were in Hong Kong, were also unable to visit, as Hong Kong had closed its border.

As a result, for the first few months of Adriana’s life, it was “just us three,” Lam told The Post. There were no play dates or visits from family and friends, and Adriana wasn’t regularly exposed to children her own age until she turned 1.

Lam thinks the prolonged isolation had some impact on her daughter Adriana. At her two-year checkup, doctors told Lam that Adriana had “weak” gross motor skills — actions like jumping and walking that engage the whole body. “I guess it’s because we only let her play in the park when she turned 1-ish because we thought it’s not safe” because of the pandemic, Lam said. Adriana was also easily startled by loud noises, such as motorcycle exhausts.

It’s difficult, Lam says, to disentangle how much of this is inherent to who Adriana is, and how much is tied to the unusual circumstances of her first year of life. But her observations echo the findings of studies that are beginning to suggest that lockdowns and the pandemic did affect children — though how much and through what mechanisms remains a largely open question.

The Irish study, published this month in the British Medical Journal, asked parents of 309 babies born between March and May 2020 to report on their child’s ability to meet 10 developmental milestones at age 1 — including the ability to crawl, stack bricks and point at objects. The researchers compared those parents’ responses to data collected on over 1,600 babies as part of a large-scale study that followed babies born in Ireland between 2008 and 2011 and assessed their development over time.

There were some small but significant differences between the two groups. Fewer babies in the study could wave goodbye — 87.7 percent compared to 94.4 percent, point at objects around them — 83.8 percent compared with 92.8 percent, or say at least one “definite and meaningful word” — 76.6 percent compared to 89.3 percent — at their 12-month assessment, according to their parents. They were more likely than their pre-pandemic peers to be able to crawl at age 1, however. In the other six categories, the researchers found no meaningful differences.

Studies that rely on observations can identify differences but not shed light on the reason for the difference. However, the authors of the Irish study have some theories.

They suggest that the babies in the lockdown cohort may have had fewer visitors, and so fewer occasions to learn to wave goodbye. With limited trips outside of the house, babies may have seen fewer few objects they’d want to point to. And they may have “heard a narrower repertoire of language and saw fewer unmasked faces speaking to them,” due to lockdown measures.

Conversely, lockdown babies may have learned to crawl faster because they spent more time at home, playing on the floor, “rather than out of the home in cars and strollers.”

“The jury is still very much out in terms of what the effects of this pandemic are going to be on this generation,” Dani Dumitriu, an assistant professor of pediatrics at Columbia University who was not involved in the Irish study, told The Post.

Dumitriu, who is a co-author of a separate study on babies born in 2020, characterized the findings as reassuring. “They’re not finding major developmental delays, just like we didn’t.”

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The study, which was peer-reviewed, has some limitations. It relies on parents’ observations of their own children, which can be flawed or incomplete. There were demographic differences between the population of pre- and post-pandemic babies, and in each case, the parents were asked to assess their children’s development “in a slightly different way.”

What is needed, the authors and other experts say, is a large-scale study that follows babies over time and measures their development in standardized ways — what’s known as a longitudinal cohort study. The authors of this study assessed the cohort of lockdown babies when they turned 2 with a standardized set of developmental questionnaires, and hope to publish their findings, which are under review, in a follow-up paper.

In the meantime, the authors of the study say most babies can overcome any delay caused by the pandemic with the right support. Researchers who have studied this cohort of babies have called on governments to provide more resources to families of lockdown babies — particularly those most at risk — and to follow those babies over time to ensure there are no long-term delays. “If we do notice a delay, then we can quickly intervene and set that child back onto a correct trajectory,” Dumitriu explains.

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Ultimately, Byrne is hopeful that “with the reopening … babies will really thrive.”

“There is such scope for plasticity in the brains of babies and children,” she told The Post.

Lam is also optimistic that Adriana will catch up with any delays as she gets older. “People around me are telling me, once they go back to study in a school, then they’ll be fine,” she told The Post. “I believe that as well.”