Influence of seasonal birth in humans

Seasonal variation in human birth rate has been found to be a nearly universal phenomenon. Also, birth seasonality has been found to be correlated with certain physiological and psychological traits of humans and animals. 
Some Findings.
Influence on medical conditions.
The season in which babies are born can have a dramatic effect on their future risk relating to the development of conditions such as neurological disorders, including seasonal affective disorder, bipolar depression, schizophrenia and type I diabetes. Research has shown that the season a baby is born in can have a major effect on whether or not you will become a heavy smoker. This even varies between men to women.
Large-scale population analytic studies.
Recently, large-scale population analytics have allowed for the exploration of birth month/season hypotheses among large cohorts of people. One study used 1.7 million patients from Columbia University in New York City (NYC) to confirm associations between neurological conditions, respiratory condition and reproductive conditions with birth month. In addition, they uncovered an association between cardiovascular diseases and birth month. This was subsequently confirmed in a separate study, also using data from NYC. Researchers also explored mechanisms correlated with birth season in a large population study including data from 10.5 million patients, from three countries (US, South Korea, and Taiwan) and six study sites. They found correlations between relative age and school cutoff periods. And that first trimester exposure to fine air particulates increased the risk of atrial fibrillation later in life.
The relationship between birth month/season and increased risk of cardiovascular disease was also confirmed in a study of close to 130,000 canines. The birth season association was found among dogs not genetically predisposed to cardiovascular disease.
As a factor in infant growth.
The season during which a birth takes place has been linked to the weight development of the infant as well as initial weight.
As a factor in academic development.
There is evidence that suggests that children who are born earlier while they attend the same academic year with others, gain an advantage: 
As a suicide risk factor.
Birth rates of people who later complete a suicide show disproportionate excess for April, May and June compared with the other months. Overall, the risk of suicide increases by 17% for people born in the spring–early summer compared with those born in the autumn–early winter; this risk increase was larger for women (29.6%) than for men (13.7%).
Research works in Sweden show that those who preferred hanging rather than poisoning or petrol gases were significantly more likely to be born during February–April. Maximum of the month-of-birth curve for preferring hanging was for March–April and the minimum was for September–October.