There’s no set amount of alcohol that’s known to cause FAS, but experts advise against any alcohol consumption during pregnancy.

Fetal alcohol syndrome (FAS) is a type of fetal alcohol spectrum disorder (FASD). These disorders can occur in people who are exposed to alcohol before birth.

FAS may affect the central nervous system, delay growth, and alter the appearance of facial features. People with this condition may also develop problems with their vision and hearing, as well as difficulties with learning, memory, and communication.

This article outlines how much alcohol it takes to cause FAS. We also discuss whether the level of alcohol consumption — and the frequency and timing of alcohol consumption — during the different stages of pregnancy increase the risk of FAS.

There are no strict guidelines on how much alcohol it takes to cause FAS. However, higher levels of alcohol consumption during pregnancy are associated with more severe forms of FASD. Still, there’s no proven “safe” level of alcohol consumption during pregnancy.

The National Institute of Alcohol Abuse and Alcoholism (NIAAA) states that the severity of alcohol’s effects on a fetus mostly depends on the following factors:

  • Quantity: Quantity refers to how much alcohol you drink per occasion while pregnant.
  • Frequency: Frequency refers to how often you drink while pregnant.
  • Timing: Timing includes the stage of pregnancy in which you drink and whether you drink heavily while the fetus is developing certain brain regions or facial features. Alcohol consumption at any stage of pregnancy can affect brain development, while heavy alcohol consumption during the first trimester can also disrupt facial development.

Again, there’s no safe level of alcohol consumption during any stage of pregnancy. However, plenty of people consume alcohol in the early first trimester, before realizing they’re pregnant.

In fact, a 2017 study involving almost 1,500 participants found that 60.6% of them drank alcohol in the period between conception and learning they were pregnant.

According to the United Kingdom’s National Health Service (NHS), you don’t need to worry too much about any alcohol consumed very early on, before you knew you were pregnant. As long as you avoid drinking for the remainder of your pregnancy, the risk to the fetus should be low.

Read more about drinking during early pregnancy.

Although medical professionals advise against drinking any alcohol at any stage of pregnancy, having one drink over the entire course of pregnancy is unlikely to raise concerns, according to the NHS.

If you have consumed alcohol at any stage of your pregnancy, consider informing your doctor or midwife, who may schedule regular prenatal checkups to check for any irregularities.

If you’re concerned about telling your care team about your alcohol consumption, it may help to know that alcohol consumption during pregnancy isn’t as rare as you may think. In the 2017 study discussed above, just over 18% of participants continued drinking after learning they were pregnant, but it’s unclear how many went on to have children with FAS.

The sooner you inform your care team, the sooner they can start monitoring the fetus for any unusual development.

If you have concerns that your child may have FAS or FASD, you can ask your doctor for a referral to one of the following specialists:

  • a clinical geneticist
  • a developmental pediatrician
  • a child psychologist

The FASD United website also features a searchable resource directory, which allows access to the following:

  • specialist FASD clinics and doctors in your local area
  • professional information and advice about FAS and other types of FASD
  • confidential support

If you’re trying to stop drinking while pregnant or trying to get pregnant, consider seeking help from the following sources:

The thought of quitting may feel daunting, but there’s no need to go through the process alone.

Alcohol consumption during pregnancy can cause FADS. There’s no safe level of alcohol consumption at any stage of pregnancy, so experts advise that people avoid drinking altogether when pregnant or trying to become pregnant.

It’s generally a good idea to inform your care team of any alcohol you consumed while pregnant. You can also talk with them if you have concerns about your alcohol consumption, are trying to quit drinking, or are worried about the possibility of FASD. They can offer advice and steer you toward the appropriate resources.