Auckland University researchers have found that overweight fathers are more likely to have undersized babies.
The findings, which have been published in the journal Obesity, come from a study that looked at more than 2000 couples in Auckland and Adelaide.
Small babies are more likely to be stillborn, and to have complications following birth and later life.
Lead researcher Professor Lesley McCowan says there is an almost two-fold increase in the risk of a baby being undernourished at birth when its father is overweight.
She says that suggests paternal health has a role to play in pregnancy complications and more research will be done to explore that.