A University of Auckland study of families has found that more than 7% of relationships broke up shortly after the birth of a baby.
The longitudinal study Growing Up in New Zealand, which is charting the lives of 7000 people from birth to age 21, has released its second lot of findings detailing the babies' first nine months.
Between pregnancy and when the child was nine months old the number of homes with only one parent doubled to 7.4%.
Study director Dr Susan Morton told Radio New Zealand's Insight programme that the mothers most likely to move out of relationships were teenagers, those without many qualifications and those living in the most deprived areas.
A third of the parents studied told researchers their baby has been watching television since it was a newborn.
Some admitted their pre-birth ideals to limit television viewing were shattered once they were faced with the gruelling realities of parenting.
Three-quarters of the babies also spent much of their day in a room where a television was on in the background.