New Zealand mothers are falling short of international guidelines for the length of time that babies should be breastfed.

An Auckland University study suggests almost all Kiwi kids are breastfed initially, but this drops to just over half by the age of four months.

Co-author Professor Cameron Grant told Rachel Smalley the World Health Organisation recommends babies should be exclusively breastfed to six months.

"And then continue to have some breast feeding up to two years of age, with obviously other appropriate complementary feeds."

The study shows that target is being met by just 16 per cent of Kiwi mothers.

Grant said rates of breastfeeding tend to be a bit lower in developed countries than developing countries.

LISTEN TO CAMERON GRANT TALK WITH RACHEL SMALLEY ABOVE