Prematurity ruled out as cause of high incidence of low birth weight in Aboriginal babies
University of Queensland researchers have ruled out prematurity as the cause of the high incidence of low birth weight in Aboriginal babies.
The finding, presented to the Perinatal Society of Australia and New Zealand conference in late March, paves the way for further research to determine why Aboriginal newborns are on average almost 400 grams lighter than their Euro-Caucasian counterparts.
According to the chief investigator, deputy head and professor of obstetrics and gynaecology at the University's North Queensland Clinical School, Professor Michael Humphrey, Aboriginal women are approximately twice as likely to have low birth weight babies (less than 2500 grams) than Euro-Caucasian women.
Lower birth weight was a significant factor in the higher infant mortality rate among North Queensland Aboriginal populations, he said. Around 78 percent of indigenous perinatal deaths occurred to babies weighing less than 2500 grams compared with 66 percent of non-indigenous baby deaths.
Professor Humphrey and research midwife Debbie Holzheimer examined 77 Aboriginal women and their babies from the Cape York communities of Lockhart River, Aurukun, Pormpuraaw and Kowanyama as well as 75 Euro-Caucasian women and babies from Cairns.
Professor Humphrey, who is also director of obstetrics and gynaecology at Cairns Base Hospital, and Ms Holzheimer recorded length and circumference measurements using ultrasound of foetuses at four stages during pregnancy and length and weight measurements when newly born.
The study represented the first time the incidence of low birth weights in Aboriginal pregnancies had been examined prospectively (from early pregnancy) and longitudinally. In the few previous studies, research was based on retrospective data and memory.
Professor Humphrey said the study clearly showed Aboriginal babies were on average lighter (by more than 350 grams), shorter (by 1 cm) and thinner than their Caucasian counterparts but that these differences were not due to babies being born on average 4.5 days earlier than Euro-Caucasian babies.
By being able to precisely date each baby for the first time, the researchers dispelled previous theories that the discrepancies were due to babies being born prematurely, showing instead that Aboriginal babies were just as likely as Euro-Caucasian babies to be born at full term.
This precise dating, through ultrasound, was only possible through the establishment of a specialist obstetrics and gynaecology outreach service - Far North Regional Obstetrics and Gynaecological Service (FROGS) - by Professor Humphrey in 1992. At the time, he was the only full-time specialist in the area. He is now one of just three.
"Trust, greater awareness and accessibility to health services through the outreach service now means Aboriginal women are presenting much earlier - around nine and 10 weeks - for their first scan. In the past and for a variety of cultural reasons, pregnant Aboriginal women usually visited the doctor for the first time well after 20 weeks. This made it extremely difficult to accurately age the unborn baby and predict the birth date," Professor Humphrey said.
He said the outreach service and other work being done in Aboriginal communities by health workers was behind a dramatic decrease in Aboriginal baby deaths in the region in the past nine years. The mortality rate in Far North Queensland stood at approximately 25 per 1000 births in 1990, falling to about 11 per 1000 births last year, he said.
Professor Humphrey said further research was now needed to determine the influence of tobacco, nutrition or familial characteristics on the lower birth weights of Aboriginal babies.
"This project has involved much consultation and negotiation with Aboriginal communities. It will form the basis of my PhD thesis and on completion, I will present the findings to the Cape York Health Council for their consideration and possible future action," Professor Humphrey said.
He said Cairns-based visiting medical officer and paediatrician Nicola Previtera was seeking funds to conduct a longitudinal study of the nutrition and welfare of all the babies involved in the study as they grew up.
For more information, contact Professor Humphrey (telephone 07 4050 6830).
