Heavy ingestion of alcohol has been implicated in an increased risk of preterm birth [203-207]. However, some studies reported modest inverse associations between low levels of alcohol consumption and preterm delivery with low birth weight (e.g., [206;208]), although this may be a result of a higher prevalence of such drinking behaviour among women who are more socio-economically advantaged [203;204]. Further, the risks associated with different dimensions of drinking during different phases of pregnancy are unclear. For example, moderate amounts of alcohol increased the risk for preterm delivery during late pregnancy, but not during early pregnancy in one study [206], whereas another study found elevated risk of preterm birth complication also with drinking in early pregnancy [209].
