The time of year when a baby is born can affect their growth. This is especially true for kids born in Estonia between 1937 and 1962. The amount of sunlight a mother gets during pregnancy can change the nutrients available to the baby. This includes vitamin D and other important minerals. However, it's not clear when during pregnancy the baby is most affected by this sunlight. It's also not clear which parts of the baby's growth are most affected.

Researchers looked at 11 different measurements of growth in Estonian kids. They found that nine of these measurements changed with the season of birth. But these changes were small. They were much smaller than the effects of the family's social and economic position. Kids from families with more money and better jobs grew more evenly. Their growth was less affected by outside factors. This includes the amount of vitamin D and other nutrients from sunlight.

For most measurements, kids born in the spring and summer were bigger. This was especially true for hip width, trunk length, and weight. These measurements showed the most clear changes with the season. If these changes are because of sunlight, it suggests that sunlight helps growth towards the end of pregnancy. Another possibility is that kids born in the spring and summer got more nutrients in the first few months after birth. This is because there is more food available in the spring and summer.

The effects of sunlight and nutrients were more noticeable in kids from poorer families. This is because their growth is more affected by outside factors. Kids from richer families had more stable growth. Their growth was less affected by changes in sunlight and nutrients. This shows that money and social position can affect how a baby grows. It also shows that sunlight and nutrients are important for growth. But they are not the only factors.

It's important to note that the effects of birth season on growth are small. They are much smaller than the effects of family background. This means that while birth season can affect growth, it's not the most important factor. Family background, including money and social position, is more important. This is something to think about when considering how to support healthy growth in kids.

How Birth Time Affects Kids' Growth in Estonia

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