Researchers have found that baby girls who are born very late are more likely to be obese when they grow up.
They believe a post-term birth can change how a person's metabolism works.
Two weeks may not seem like a long time, but it could be the difference in a baby girl being overweight or not later in life.
"Women who were born post-term -- in other words, at 42-weeks of gestation or later -- had a slightly increased risk of obesity in adulthood," says University of Auckland researcher Dr Jose Derraik.
Research from the Liggins Institute looked at more than 200,000 women over an eight-year period.
Baby girls born at 43-weeks or later were an average of one kilogram heavier, and 12 percent more likely to be obese later in life than those born at normal term.
"They had more body fat, more abdominal body fat and their body was also not as good at handling sugar in their blood stream," says Dr Derraik.
That means they also have an increased risk of developing type-two diabetes and cardiovascular disease.
It's not just girls -- previous studies which initiated this research found baby boys born late were linked with obesity in teenage years.
"It could be because of deterioration of the placenta late in gestation, or it could be to other stressors earlier in pregnancy," says Dr Derraik.
Researchers hope the findings will empower people who were born post-term to make better lifestyle choices to minimise their risk of obesity and health problems later in life.