Methods
This is a population-based cohort study based on data from The Swedish Pregnancy Register [The 64,632 women were divided according to BMI when registered at the maternity clinic in the first trimester, defined as a person’s weight in kilograms divided by the square of the person’s height in meters (kg/mThe study was approved by the Regional Ethics committee in Stockholm, Sweden (Dnr 2015/2105–31/1).