Women who aren't on birth control shouldn't drink alcohol, CDC says

Drinking alcohol during pregnancy is "associated with a range of complications and poor reproductive outcomes and can cause fetal alcohol spectrum disorders (FASDs), which are characterized by lifelong physical, behavioral, and intellectual disabilities," the CDC report said, adding that exposure to alcohol in the womb is one of the leading preventable causes of intellectual disability in children.

It can also "increase the risk of miscarriage, stillbirth, prematurity, and sudden infant death syndrome (SIDS)," the CDC said.

The sight of a woman sipping a glass of wine during her pregnancy is common in many parts of the world and deemed by many to be socially acceptable.

A CDC report in 2015 found that one in 10 pregnant women in the United States reported drinking alcohol in the previous 30 days, and 3% reported binging -- defined as four or more alcoholic drinks in two to three hours.

Some countries showed more alarming data: In a study published in the British Medical Journal, drinking rates were found to be as high as 80% during pregnancy in Ireland, and between 40% to 80% in the UK, Australia and New Zealand.

The CDC warns there are no known safe limits of alcohol during pregnancy.

"Alcohol compromises a number of systems that support the baby," said Philip May, research professor at the Gillings School of Public Health at the University of North Carolina, Chapel Hill. "(For example) nutrients like iron won't reach the fetus for proper development," he said.

May has been studying FASDs for more than 30 years, and recent work by his team revealed surprising new estimates for the number of children affected by these disorders in the United States.

"We have estimated rates of 2-5% in the general population and it's probably very similar for many countries in Europe," he said.

The conditions span a spectrum because symptoms can vary dramatically and can develop at different stages of life. Symptoms include growth and facial development challenges, but more often behavioral and intellectual disabilities such as hyperactivity, poor language skills, concentration and poor math skills -- most of which are not obvious at birth and difficult to diagnose before children reach school age.

"It's much more common than we thought," said May.

Five levels of disorder fall within the spectrum: the milder fetal alcohol effects, then alcohol related birth defects, alcohol related neurodevelopmental disorder, partial fetal alcohol syndrome and the most severe, fetal alcohol syndrome.

"Ninety percent of all outcomes from drinking during pregnancy affect the baby's central nervous system," said Denis Viljoen, chairman of the Foundation for Alcohol Related Research in South Africa. "It's a disability that remains throughout life."

Health officials said some mothers who did drink during previous pregnancies may not see a problem with the practice because their other children turned out fine, but experts caution that reasoning isn't safe because each individual is different -- and the severity of the effects of alcohol exposure is known to increase in subsequent children.

"The disorder is always worse in later-born kids," May said.

Viljoen says as many as 1-2% of global birth defects are the result of FASD.

Populations in Croatia, Australia and Italy have been studied and found to have more cases than expected, as the disorder is easily missed by health professionals.

"Many children with FAS go to school and they're not doing well but nobody knows why," said May. In one of his studies, May found that around 16% of children with FAS had not been diagnosed by the time his team examined them at age seven. "Approximately 80% go undiagnosed," he added.

South Africa has one of the highest rates of people affected by FASD, estimated to be 11.3%.

"It's completely out of proportion," Viljoen said.

The rates are influenced by socio-economic factors, he explained, with drinking during pregnancy more common among deprived communities with poor educational backgrounds and living conditions. "There is a heavy drinking problem in our poorer populations," he said.

Alcohol is rapidly absorbed inside the body, transmitting throughout the organs within half an hour, according to Viljoen. "It's rapidly absorbed and crosses the placenta," he said. Once inside the fetus, alcohol can damage growth and nerve cells during development.

"These kids all have mild to moderate mental retardation," Viljoen said. The impact is greatest among the children of heavy drinkers and the consequences of light drinking are more hotly debated, with no agreement among experts on an acceptable level of alcohol consumption during pregnancy.

Various factors relating to the mother also come into play, such as her body mass Index (BMI) and nutrition levels.

A 2013 study by University College London found that light drinking during pregnancy does not appear to harm a child's intellectual development. One in four mothers in the study reported they were light drinkers during pregnancy, one in 20 said they were moderate drinkers and 2.5% were heavy drinkers. Some children in the group did develop problems, including hyperactivity and social challenges with peers, but few issues were found in the children of light drinkers.

Viljoen and May, however, believe women trying to become pregnant or who are pregnant should abstain from alcohol -- a view supported by the CDC and the American Academy of Pediatrics. The spectrum of conditions related to fetal alcohol exposure is completely preventable, experts say.

"We'll never prevent it completely, but prevention is the secret of the whole thing," said Viljoen.