University of Cambridge, UK, looked at whether birth month had an effect on birth weight, onset of puberty, and adult height. They found that children who were born in the summer were slightly heavier at birth and taller as adults and went through puberty slightly later than those born in winter months. The researchers compared the growth and development of around 450,000 men and women from the UK Biobank study, a major national health resource that provides data on UK volunteers to shed light on the development of diseases. The results reveal that babies born in June, July and August were heavier at birth and taller as adults. For the first time, the study also revealed that girls born in the summer started puberty later, an indication of better health in adult life. The researchers believe that the differences between babies born in the summer and the winter months could be down to how much sunlight the mother gets during pregnancy, since that in part determines her vitamin D exposure. It is thought that vitamin D exposure is important and the effects of early life vitamin D impacts on puberty timing and health.
Scientists in Finland have found that babies born in the autumn face a higher risk of allergies to common foods such as milk and eggs. This is thought to be linked to greater exposure to tree pollen during infancy. Similarly the Columbia University study indicated people born in May had the lowest disease risk, and those born in October the highest.