Friday, September 29, 2023

How much alcohol is safe to drink in pregnancy?

No alcohol consumption is advisable during pregnancy due to its ill effects on foetal growth. Even small amounts of alcohol are not okay.

Should a woman drink alcohol during pregnancy? If yes, how much? A precious life can suffer if that decision is medically wrong. In this article, we will look at what science says about alcohol drinking during pregnancy.


In conservative cultures, women don’t commonly drink alcohol. However, with most of the world now getting westernised, drinking is increasingly becoming a socially acceptable activity for women across the globe.

Some alcoholic drinks such as wines are considered good for health and drinking them is even encouraged. So a woman may choose to drink during pregnancy if she is not aware of the potential problems.

Alcohol Metabolism

Alcohol is digested or metabolised by the liver and converted into a chemical called acetaldehyde. Normally, acetaldehyde is quickly converted into compounds called acetates and eliminated through the urine. However, if one drinks more alcohol—the definition of ‘more’ changes from person to person—the liver takes time to break down toxic acetaldehyde into harmless acetates. So the blood levels of acetaldehyde stay elevated for many hours.

In a pregnant woman, alcohol and acetaldehyde can enter her foetus through the umbilical cord.

Vitamin A and Foetal Development

Vitamin A plays a vital role in the growth of an embryo. It helps in a proper development of the internal organs of a foetus, such as the heart, lungs, kidneys, eyes, pancreas, and nervous system. Vitamin A deficiency in the mother’s body can lead to a shortfall in vitamin A in the foetus, leading to various birth defects such as mental retardation and physical deformities.

To learn how vitamin A helps in cell duplication and foetal development, read on this website: Vitamin A: A complete guide.

Why Alcohol Causes Birth Defects

Acetaldehyde, the byproduct of alcohol breakdown, has a very similar chemical structure to a form of vitamin A called retinaldehyde or retinal. As a result, cell multiplication and foetal development processes that need vitamin A to attach to certain chemical structures end up with acetaldehyde attaching in those places. As a result, those processes don’t progress properly, leading to an abnormal development of the foetal organs.

Foetal Alcohol Spectrum Disorders

Such ill-formed foetuses often lead to preterm deliveries, miscarriages, or stillbirth. Some end up with physical and mental disabilities. These are called fetal alcohol spectrum disorders or FASDs. Such children demonstrate the following symptoms:

  • Small height and head size
  • Facial deformities
  • Hyperactivity or attention deficit
  • Poor learning and reasoning ability
  • Poor memory
  • Low IQ and poor judgment
  • Speech, hearing, and language problems
  • Heart, kidney, joints, or muscle problems

How Much Alcohol is Safe in Pregnancy?

There is no clear-cut amount of time that the body takes to remove alcohol from the system. For example, after you drink alcohol, laboratory tests can detect its presence in various body parts long after you finish drinking:

Body PartTime in System
Blood6 hours
Breath12 to 24 hours
Urine72 hours
Saliva12 to 24 hours
Hair90 days
Ref: American Addiction Centres: How Long Does Alcohol Stay in Your System?

As you can see, we don’t know how long it takes for the alcohol to be out of the system. We know the time it takes for some of its effects to wane but that is not necessarily the time it would take for alcohol to stop affecting the foetal growth.

Half-Life of Alcohol

There is a concept called half-life of a chemical in the body. That is the time it takes for half its amount to be neutralised or excreted from the body.

Alcohol has a half-life of five hours in our body. So if you have 100 units of alcohol in the blood at any point, it will be 50 units after 5 hours, 25 units after 10 hours, and so on.

Typically, 5 half-lifes are considered enough to say that alcohol has been eliminated from your system. Thus, in 25 hours, the alcohol in your blood is reduced by a factor of 32. It will be 100 / 32 ≈ 3% of the starting levels.

Since this 3% is an arbitrary cutoff, mainly indicating how soon can one pass the breath test comfortably, it may not have relevance to foetal safety.

In other words, scientists don’t know the safe amounts of alcohol consumption in pregnancy. Many renowned organizations err on the side of caution. For example, the American College of Obstetricians and Gynecologists, the American Pregnancy Association, the American Academy of Pediatrics, and the UK’s Royal College of Obstetricians and Gynaecologists advise no alcohol consumption during pregnancy.

Earlier research had shown that heavy drinking can cause foetal abnormalities. However, new research is showing that a low level of alcohol use by a mother also affects a child’s brain development.

What about mild forms of alcohol, such as wines? Many experts discourage that consumption, too. In fact, wines have some of the highest acetaldehyde contents among various alcohols.

In my view, a peg of alcohol once a month or two is not likely to be harmful. However, the best option is to stay away from alcohol during pregnancy.

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First published on: 5th July 2022
Image credit: Relax home photo created by gpointstudio –


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