A new study shows mothers are losing out financially after having a child.
Motu Research has found there is a 12 percent hourly wage difference between men and women who are parents, compared to six percent without children.
The study, carried out by economists for the Ministry for Women, is believed to be the first in the world which measured the incomes of an entire population of people from five years before they had their first child to 10 years after the child's birth.
Lead researcher Dr Isabelle Sin says women who return to work faster suffer less with their pay packet.
"Mothers who return to work within six months have a statistically insignificant decrease in their hourly wages, but they do suffer from slower wage growth in the future."
She says it's one explanation for why women are missing from the country's top income groups.
"These are the women who were about to be the top earners in the economy, but because they've had children they end up falling a long way below their high-income male peers."
Dr Sin says New Zealand workplaces need to become more family-friendly and accepting of parents' choices around childcare.
"They learn, they know how to handle it. Look at the rest of the world for goodness' sake."