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A healthy baby.

Children born at a particular time of year have more ear and other infections. A new study from the U shows why.

Happy (healthy) birthday to you!: When a baby is born is a predictor of childhoo

When a baby is born is a predictor of childhood health

From M, winter 2005

University professor Chap Le and his colleagues have shed light on a confounding public health problem: why children born at a particular time of year have more ear infections.

We've all heard of family planning, but Le's research could take this concept to a new level. Le found that the time of year a baby is born can be a strong predictor of newborn health. In a study published in the journal Statistics in Medicine, Le and colleagues from the School of Public Health and the School of Medicine developed a statistical model that correlates birth date and the occurrence of ear infections.

In doing this, Le and colleagues examined cord blood samples from 600 infants to measure the level of pneumococcal antibodies. Pneumococcal bacteria can lead to a host of childhood infectious diseases, among them otitis media, commonly known as ear infection.

The data showed that the occurrence of otitis media among babies born in the early fall is much higher that of those born in early spring. This seasonal aspect of disease occurrence is not new, especially for infectious and respiratory diseases. What's new is the remarkable finding that infants born in the fall have less than half the antibody levels compared to those born in the spring, a result of the mother's lack of recent exposure to pneumococcus before the baby is born.

Here's how it works: In the winter months, the expectant mother is likely to spend time in a sealed house, exposing herself to indoor air pollutants such as pneumococcus. She builds up antibodies and transfers them to her unborn child through the placenta. Thus, babies born in early April have the benefit of a high level of antibodies and are less apt to get sick.

Conversely, in the summer, the expectant mother spends more time outdoors and in a home that allows for more air exchange. Thus, she doesn't build up antibodies to infectious disease and her baby born at the end of September has a low level of antibodies, as well. This is compounded by the fact that the season is changing, homes are sealed against the cold, the baby is exposed to more indoor air pollution, and is thus more likely to get sick.

The study highlights the conflicting role of indoor air pollution: bad for the mother, but in the end, good for those babies born in the spring.