Numbers of women drinking during pregnancy are higher than expected. One in 10 pregnant women reported drinking in the previous 30 days, with more than 3% reporting to binge, in a 2015 report by the US Centers for Disease Control and Prevention.
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The CDC estimates that millions more women in the US are exposing babies to alcohol during development by not realizing they are pregnant.
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A CDC report found that 3.3 million women were putting their fetus at risk by drinking alcohol while sexually active and not practicing birth control.
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Rates of drinking have been found to be as high as 80% during pregnancy in Ireland and between 40% to 80% in the UK, Australia and New Zealand in other studies.
Exposure to alcohol in the womb is one of the leading preventable causes of intellectual disability in children along with a range of physical, behavioral and intellectual disabilities known as fetal alcohol spectrum disorders.
Five levels of disorder fall within the spectrum starting with the milder fetal alcohol effects and building up to alcohol-related birth defects, alcohol-related neurodevelopmental disorder, partial fetal alcohol syndrome and then the worst of them all, fetal alcohol syndrome.
Globally, rates of fetal alcohol spectrum disorders are thought to be 1% to 2% of all birth defects. South Africa tops the list with 11.3% of the population estimated to be affected by these disorders in a recent study.
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In the US, rates of fetal alcohol spectrum disorders are estimated to be up to 5% among school-age children.
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Impact will vary depending on when during development the fetus was exposed to alcohol. Facial abnormalities occur mainly during the first trimester, but risks to the central nervous system remain throughout.
Alcohol can cause damage because it is rapidly absorbed inside the body and transmits throughout the body's systems within half an hour. It then crosses the placenta and gets inside the fetus, alcohol can go on to damage growth and nerve cells during development.
An estimated 90% of all outcomes from drinking during pregnancy affect the baby's central nervous system, according to Denis Viljoen, chairman of the Foundation for Alcohol Related Research. Experts advise women not to drink as soon as they stop using birth control.