Women who drink heavily during their first trimester have a significantly higher risk of delivering their baby prematurely compared to women who drink little or not at all, a new study suggests.

In a study of more than 4,000 Australian women, researchers found that women who drank moderate to high levels of alcohol in their first trimester and then stopped before their second trimester were 73 per cent more likely to deliver a preterm baby.

The study, published in BJOG: An International Journal of Obstetrics and Gynaecology, also found that drinking low levels of alcohol in the first trimester did not increase a woman's odds of delivering a preterm infant.

"Alcohol intake at higher levels, particularly heavy and binge drinking patterns, is associated with increased risk of preterm birth even when drinking is ceased before the second trimester," the authors concluded. "This finding, however, is based on small numbers and needs further investigation."

The issue of how much alcohol is safe during pregnancy is a controversial one. Women are generally advised to cease drinking while pregnant, and there is a growing body of research to support this recommendation.

In December, a study published in the journal Alcoholism: Clinical & Experimental Research, found that prenatal alcohol exposure damages the white matter in a fetus's developing brain.

White matter is a bundle of nerve fibres that transfer information between different regions in the brain.

Damage to white matter may help explain the cognitive and behavioural problems experienced by children who suffer from fetal alcohol syndrome.

The authors of this latest study suggest further research on the effect that dosage and timing of prenatal alcohol exposure can have on preterm birth and other health risks.