Babies born at two New York City hospitals in 2020 during the COVID-19 pandemic scored slightly lower on developmental tests at 6 months of age than did babies born before the pandemic, according to a new study. There were no significant differences between the groups in communication and problem-solving skills.
The study, published in JAMA Pediatrics today, found that 6-month-old pandemic-era infants scored slightly lower in motor and social skills, as reported by their mothers in a widely used developmental assessment.
“These were not large differences … just small shifts in average scores between the groups,” says lead investigator Dani Dumitriu, a pediatric hospitalist at Columbia University, who suggests parental stress may be contributing to the gap. “But these small shifts warrant careful attention because at the population level, they can have a significant public health impact.”
She adds that for individual babies, this slight slowing of neurodevelopment doesn’t necessarily predict long-term outcomes. “At 6 months, babies are extremely malleable—their brains are so ready for getting back on their neurodevelopmental trajectory.”
Other researchers point out that the study examined fewer than 300 infants, and that groups born before and during the pandemic had different characteristics; they say the results should be interpreted with caution.
“This is a nice example of ‘responsive science’—research addressing real-world questions as quickly as possible; the downside is that we shouldn’t expect complete or wholly reliable … conclusions,” says Tom O’Connor, a psychologist at the University of Rochester who studies prenatal stress and its effect on children.
A few previous studies have looked at pandemic-era babies’ development. An August 2021 preprint, not yet peer reviewed, from researchers at Brown University found significantly reduced verbal, motor, and overall cognitive performance in infants born after July 2020 compared with those born before 2019. And a study from China, published in October 2021 in Frontiers in Pediatrics, found fine motor delays in 1-year-old infants born in the spring of 2019 compared with 1-year-olds born in the springs of several prior years.
For the current study, the researchers looked at developmental scores of 227 pandemic-era infants born at two northern Manhattan hospitals, New York-Presbyterian Morgan Stanley Children’s Hospital and New York-Presbyterian Allen Hospital. The team compared those infants with 62 babies born at one of the hospitals in the 2 years preceding the pandemic.
In both groups, mothers completed a common neurodevelopmental test during the infant’s fifth or sixth month of life. Its 30 questions assess motor, communication, problem-solving, and personal-social skills, such as whether an infant turns its head toward a loud noise, reaches for a Cheerio, or rolls from its back to its stomach.
The prepandemic and pandemic groups differed demographically, but the researchers say their analysis adjusted for these differences, including the infant’s sex and gestational age at birth and the mother’s age, race, ethnicity, educational level, and prior pregnancies.
The researchers found babies’ fine and gross motor skills and their personal-social score—gauged by behaviors such as whether an infant coos at itself in a mirror or interacts differently with strangers than with caregivers—were significantly lower in infants born between March and December 2020 than in babies born prepandemic.
The lowest scores occurred in infants born to mothers who were in their first trimester of pregnancy during the first peak of the pandemic in New York City, which the team defined as 7 March to 6 April 2020. The scientists say this suggests maternal stress as a possible mechanism and fits with previous research suggesting maternal stress early in pregnancy has a bigger effect than stress later in pregnancy on infants’ socioemotional functioning.
The study comes with caveats, including that mothers’ reporting of their babies’ abilities may be biased by parental perceptions, and that it’s difficult to assess development in 6-month-olds by any method.
Some scientists are skeptical. “The sample sizes in all of their groups are extremely small for making the kinds of conclusions they are making, based on group comparisons,” says Suzanne King, a developmental psychologist at McGill University who studies development in children exposed to maternal stress in utero as the result of natural disasters.
And the team’s statistical efforts to control for social factors may not have done enough to remove biases, adds Mollie Wood, a perinatal epidemiologist at the University of North Carolina, Chapel Hill. “Do we believe that [the] historical control group they are using is [a good comparison], even with doing the statistical adjustment? I’m not sure,” she says.
The team also found an encouraging result: Contracting COVID-19 during pregnancy didn’t impact the resulting babies. Within the pandemic group, there was no difference in neurodevelopment between 114 infants born to moms who had COVID-19 during pregnancy and 141 infants born to moms who didn’t. That was contrary to other research results.
“We were surprised to find absolutely no signal suggesting that exposure to COVID while in utero was linked to neurodevelopmental deficits,” Dumitriu says. “That’s really important and reassuring.”
But other scientists were hesitant about that finding, too. “This study is not evidence that COVID is not harmful in terms of children’s development later. It’s incredibly important to … get vaccinated in pregnancy,” Wood says.
Overall, O’Connor says the study highlights a critical fact: “We need to think about risk exposure during the pandemic as broader than simply the virus.”