A new study from the Telethon Institute for Child Health Research has revealed the consequences of heavy and binge drinking on pregnancy even after these drinking patterns have stopped.
The study, to be published in BJOG: An International Journal of Obstetrics and Gynaecology, investigated the relationship between prenatal exposure to alcohol and the effects on fetal growth and preterm birth.
A random sample of 4,719 women who gave birth in Western Australia between 1995 and 1997 took part in a survey. Data such as how often participants drank alcohol, the amount of alcohol consumed in each occasion and the types of alcoholic beverage consumed were collated.
The researcher team from the Institute with the National Perinatal Epidemiology Unit at the University of Oxford found that, on average, levels of alcohol intake decreased from the pre-pregnancy period to the second and third trimester. There was no difference in outcomes for women who drank low levels of alcohol during their pregnancy and those that abstained.
The incidence of preterm birth was highest amongst women who binged (9.5%) or drank heavily, even if the mother stopped drinking prior to the second trimester (13.6%), compared with less than 6% in women who did not drink during pregnancy. There was a 2.3-fold increased odds of preterm birth in women who drank heavily in early pregnancy but then stopped (CI 0.7, 7.7) after taking into account maternal smoking, drug use, socioeconomic status and maternal health. Researchers suggest that a possible reason why this occurs is because the cessation of alcohol consumption before the second trimester may trigger a metabolic or inflammatory response resulting in preterm birth. There was no evidence of an increased likelihood of preterm birth at low levels of alcohol consumption.
Prenatal alcohol exposure did not increase the risk of babies being born small for gestational age once maternal smoking was accounted for.
Researchers noted a link between smoking and alcohol consumption – they found women who smoked during pregnancy were less likely to abstain from alcohol at any time during their pregnancy than non-smokers. Over one quarter (27.7%) of women who drank in late pregnancy also smoked, compared with 19% of women who had abstained from alcohol during pregnancy. Other factors associated with late term pregnancy drinking include: a maternal age of 30 years and above, higher income, use of illicit drugs.
Institute researcher Colleen O'Leary said "Our research shows pregnant women who drink more than one to two standard drinks per occasion and more than six standard drinks per week increase their risk of having a premature baby, even if they stop drinking before the second trimester.
"The risk of preterm birth is highest for pregnant women who drink heavily or at binge levels, meaning drinking more than seven standard drinks per week, or more than five drinks on any one occasion.