Pregnant women who eat a lot of sugar-laden food could be compromising their babies' development, new New Zealand research suggests.

The study, released today by University of Auckland's Liggins Institute, found a link between sugars such as fructose and compromised foetal development.

"Obesity is now the leading cause of pregnancy complications (and) while the effects of maternal high-fat diets on offspring have been well investigated, we know very little about the effects of consuming high levels of sugars such as fructose," senior research fellow Deborah Sloboda said.

She said fructose - which naturally occurs in honey, fruit and some vegetables but is also used as a sweetener in processed foods and soft drinks - was thought to be a major contributor to obesity, she said.

In the study, where rats were fed diets high in fructose during pregnancy and lactation, the sugar was found to change key metabolic hormone levels in both foetuses and new born offspring.

The changes were sex-specific, with only females affected pre-birth.

Researchers also found the placentas supplying nutrients to female fetuses were significantly smaller than those of the males.

Dr Sloboda said while the study was conducted on rats there may be implications for humans.

"Intriguingly, the mothers on the fructose enriched diets did not gain any more weight or fat mass than animals on a regular diet, but they had higher concentrations of the hormone insulin in their blood -- a key problem in type two diabetes," she said.

"Recently, there has been a marked increase in consumption of foods and beverages sweetened with fructose, particularly amongst women of reproductive age.

"The fact that we saw no obvious weight gain implies that women may be unaware that their diet could be compromising the development of their fetus."

Preliminary data suggested fructose could affect placenta, and in turn, liver function in humans, Dr Sloboda said.