Right now is a good time to make babies
Researchers have known for decades that children born in cold months were more prone to health problems later in life, including mental illness and early death.
They speculated but had never proven that it could be from factors like harsh temperatures and higher pollution levels in the winter months. But winter months were also a time when babies from lower socioeconomic families are most often born. So it was difficult for researchers to distinguish if socioeconomic status or the seasonal patterns affected the baby's health.
They found that as far as health is concerned, January through May is the least favorable time to conceive. Babies conceived in May (thus, born in the middle of winter) had it the worst — they were 13 percent more likely be born premature, which could cause a weaker immune system, slower cognitive development and other problem later in life. Babies conceived in June through August were the healthiest.
The researchers also looked at Centers for Disease Control and Prevention (CDC) data and saw that these study results closely align with reports of flu-like symptoms. For example, when the H1N1 pandemic happened a few years ago, it started about 2 months earlier than a typical flu season. The study matched these results.
One researcher commented, "I think it really gives support to the idea that pregnant women should be vaccinated for flu."
The flu is just one likely factor. The researchers also noted that lower vitamin D levels in winter months could also be a cause.