Did Catching COVID-19 During Pregnancy Affect Children's Development? What Studies Following Children to Age Three and Four Now Show

A family-friendly guide to three 2026 studies from Norway, Massachusetts and Northern California (Magnus et al., Shook et al. and Croen et al.) and why their answers differ

Many parents who had COVID-19 while pregnant have wondered whether it could affect their child's development. Three large studies that followed children to about age three or four found mostly reassuring results: two found no overall increase in developmental diagnoses, while one smaller study found a modest increase. None can prove that the infection itself caused any difference, and routine developmental check-ups remain the best way to support every child.

If you were pregnant during the pandemic, you are far from alone in asking this question. In 2026, research teams in Norway [1], Massachusetts [2] and Northern California [3] published studies that followed children for longer than most earlier research. Below we explain what they learned, why they do not all say the same thing, and what it means for your family.

Why researchers were worried in the first place

Long before COVID-19, scientists had noticed that serious infections during pregnancy might be linked to differences in a child's development. Very large studies in Sweden, which keeps detailed national health records, found that children whose mothers were in hospital with an infection while pregnant were somewhat more likely to be diagnosed later with autism, a condition that affects communication and social interaction [4][5]. A study pooling results from 15 earlier studies found a similar small link [6]. Laboratory research in animals suggested a possible reason: when a pregnant mother's immune system fights an infection, that response itself, rather than the germ reaching the baby, can affect how the baby's brain develops [7].

But the story turned out to be more complicated. When Swedish and British researchers compared brothers and sisters from the same family, the link largely disappeared [8][9]. This suggests that shared family factors, such as genes or home circumstances, explain much of the connection, rather than the infection itself. We have written about the same issue for paracetamol use in pregnancy.

When COVID-19 arrived, the question returned. The virus only occasionally passes from mother to newborn baby, in about 4 of every 100 cases across 204 studies [10], but researchers wondered whether the mother's immune response or effects on the placenta (the organ that feeds the baby in the womb) might matter [11]. Some laboratory work found that the placenta responded differently depending on whether the baby was a boy or a girl [12]. We also know that COVID-19 in pregnancy makes premature birth more likely [13], and being born early can itself affect development.

What the early studies found, and why they were not enough

The first studies could only follow babies for their first year or two. A study from hospitals in Massachusetts, in the United States, found that babies whose mothers had COVID-19 in pregnancy were more likely to have a developmental diagnosis by their first birthday [14], mainly boys, though the difference became smaller by 18 months [15]. Other studies used questionnaires that parents fill in about what their baby can do, such as babbling, pointing and walking. These were reassuring: studies in New York City [16], across all 50 US states and Puerto Rico in the Assessing the Safety of Pregnancy in the Coronavirus Pandemic (ASPIRE) study [17], and at 23 US sites in the Researching COVID to Enhance Recovery (RECOVER) Pregnancy study [18] found no differences. Autism can be diagnosed from about 18 months of age at the earliest [19], and many children are diagnosed later than that [3], so researchers needed to follow children for longer.

Three new studies that followed children to age three or four

In 2026, three teams published studies that followed children further. All three looked back at health records: they compared children whose mothers had a positive COVID-19 test in pregnancy with children whose mothers did not, and counted how many received a developmental diagnosis from a doctor.

The Massachusetts team, publishing first, followed the same group of children from their earlier studies to age 3 [2]. Their study included 18 124 children born between March 2020 and May 2021 at eight hospitals in the Mass General Brigham system, and 861 of these children were born to mothers who had tested positive. Almost all of these mothers had not yet been vaccinated.

A team in Northern California studied 69 987 children born between January 2020 and September 2021 in the Kaiser Permanente Northern California health system, following them until they were between about two and a quarter and four years old [3]. Mothers of 2777 children had tested positive.

Finally, a team in Norway used national health records for every child born alive in the country between March 2020 and December 2023, 204 663 children in all, followed for an average of 3.6 years [1]. Mothers of 16 325 children had tested positive, mostly during the Omicron wave.

What the studies found

In Massachusetts, about 16 in every 100 exposed children had a developmental diagnosis by age 3, compared with about 10 in every 100 unexposed children [2]. After the researchers took account of differences between the families, such as age, background, insurance and premature birth, the exposed children still had a modestly higher chance, about 29% higher odds. Most of the diagnoses were speech and language delays, and the difference was mainly seen when the infection happened late in pregnancy and among boys.

In Northern California, the picture was different. About 17 in every 100 children in both groups received a developmental diagnosis, so there was no overall difference [3]. Autism diagnoses were slightly more common among girls (but not boys) whose mothers had been infected. Because this was one of many comparisons, and the difference between boys and girls could have been due to chance, the researchers call for more studies before drawing conclusions.

In Norway, the largest study, children whose mothers had COVID-19 in pregnancy were no more likely to have any of eight types of diagnosis, including autism, speech or language disorders, epilepsy and hearing or vision problems [1]. There was no difference between boys and girls or by stage of pregnancy. Only in a smaller extra analysis, limited to children born before March 2022, when COVID-19 testing was more widespread, did speech and language disorders appear more common; the researchers say this needs to be checked in other countries.

Why do the studies disagree?

It can be confusing when studies seem to say different things, but there are understandable reasons. The studies took place at different times: Massachusetts and California mostly covered the early pandemic, when most pregnant women had not yet been vaccinated, while Norway mostly covered the later Omicron period. Testing also differed. In Massachusetts, from April 2020 every woman arriving to give birth was tested, so the researchers knew more precisely who had been infected; in Norway, testing depended on symptoms and was scaled back in 2022, so some infections were likely missed.

The families also differed. In Massachusetts, mothers who caught COVID-19 were much more likely to have public health insurance, and how often families see doctors can affect how many diagnoses get recorded. When the Massachusetts team looked only at the smaller group of children who had a check-up at age 3 or later, the difference was of similar size but could no longer be told apart from chance. Growing up during lockdowns, with fewer chances to play and talk with other people, may also have affected some children's language, whether or not their mother was infected [20][21].

Finally, the patterns found in smaller groups did not repeat. Boys stood out in Massachusetts, girls with autism in California, and neither in Norway. When findings do not repeat across studies, they may be due to chance.

What this means for your family

If you had COVID-19 during pregnancy, these findings are largely reassuring. The two biggest studies, including one covering every child born in an entire country, found no overall increase in developmental diagnoses. Even in the study that did find an increase, the large majority of exposed children (all but about 16 in every 100) had no developmental diagnosis by age 3.

The most helpful thing you can do is the same as for any child: attend routine check-ups, where your child's doctor or nurse will look at speech, movement and social skills, and share any concerns early. Doctors in the United States recommend checking all toddlers for signs of autism at 18 and 24 months [19]. If a difference is found, early support helps, whatever the cause. It can also help to tell your child's doctor that you had COVID-19 in pregnancy, so it is on record. If your baby was born early or needed neonatal intensive care, your baby may already have extra follow-up for that reason.

It is also worth knowing that a large Scottish study found that COVID-19 vaccination in pregnancy appeared safe when it came to early developmental concerns [22].

What researchers are working on next

Researchers want to follow these children into school age, when conditions such as attention difficulties can be recognised. They also hope to compare brothers and sisters, collect information on how ill mothers were, and check whether the findings in boys or girls hold up.

The bottom line

Three large studies following children to about age three or four mostly found no increase in developmental diagnoses after COVID-19 in pregnancy, and the one that did found a modest difference that has not been confirmed elsewhere. For families, routine check-ups and early conversations with your child's care team remain the best way forward.

References

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