Owing to higher level of outdoor air pollution during summers, dogs born during this time are more likely to be at higher risk of heart disease, according to a study.
For both dogs and humans, outside air pollution during pregnancy and at the time of birth appears to play a role in later development of heart disease.
Overall, dogs have a 0.3 to 2 per cent risk of developing heart disease depending on breed, but among those that are genetically predisposed to the heart disease, the birth month difference in risk was found to be marginal.
However, breeds not genetically predisposed to the disease, such as Norfolk terrier, Berger Picard, American Staffordshire terrier, English toy spaniel, Bouvier des flandres, Border terrier and Havanese were also found to be at highest risk.
This suggests that the effect supports an environmental mechanism, the researchers said, in a paper published in the journal Scientific Reports.
The study, published in the journal Scientific Reports, also supports earlier findings in humans pointing to the role of early gestational exposure to fine air particulates and increased risk of heart disease later in life.
"It's important to study dogs because the canine heart is a remarkably similar model to the human cardiovascular system," said Mary Regina Boland, Assistant Professor at the University of Pennsylvania in the US.
"Also, humans and dogs share their lives together and are exposed to similar environmental effects, so seeing this birth season-cardiovascular disease relationship in both species illuminates mechanisms behind this birth-season disease relationship," Boland added.
Because dogs' pregnancies are shorter than humans (lasting only 2 months), pollution as a possible mechanism is still thought to be through the mother's inhalation of air pollution effecting the uterine environment, which in turn affects the developing cardiovascular system of the baby or puppy, the study showed.
For the new study, the team examined 129,778 canines encompassing 253 different breeds.
The research team found that risk climbs to the greatest level in dogs born in July, who have a 74 per cent greater risk of heart disease than would typically be expected.