Pregnant women are being warned that vehicle crashes account for more than half of all New Zealand's foetal deaths due to a maternal injury, according to a new study.

The University of Otago study found that of the 41 foetal and newborn deaths due to maternal injury between 1997 and 2008, 21 involved motor vehicle collisions.

The university's Injury Prevention Research Unit director Professor Hank Weiss said he found the rate of foetal death resulting from such crashes was about twice that of infant crash-related deaths in New Zealand.

The research also showed that while Maori made up 15 per cent of the population, they account for 27 per cent of the foetal deaths due to maternal crash injury.


"This outcome may be partly driven by Maori women having higher birth rates at younger ages when they are at greater risk of being in a crash," Prof Weiss said.

Foetal death and injury due to maternal injury was a largely invisible but important component of child injury mortality, he said.

"The problem remains hidden, and under-reported, because of the way foetal trauma is coded in vital statistics and the lack of pregnancy status recorded in crash and injury surveillance systems."

The research was published in the latest issue of the journal Australian Epidemiologist.

Prof Weiss said there needed to be more attention paid to reporting and preventing maternal injuries and adverse foetal outcomes.

Ministry of Transport data showed that from the early 1990s to the mid 2000s the average annual distance driven per woman for ages 15-39 increased by about 40 per cent to 7000 km, which contributed to increased exposure to the risk, Prof Weiss said.

He recommended a combination of increased protection for vehicle occupants, less driving and less risky driving to suit different lifestyles.