While no amount of alcohol is safe during pregnancy, drinking small amounts before realizing you’re pregnant likely won’t cause any harm.

It happens. Perhaps you went off birth control a few months ago to try for a baby, but weren’t expecting to get pregnant so soon. You did cut back on alcohol to up your chances of conceiving, but you continued having a glass of wine here and there.

Or maybe you weren’t trying to get pregnant at all, and it came as a surprise when you realized that your period was over a week late. Now you’re looking at two pink lines on a home pregnancy test and freaking out about the night out with your girlfriends that you enjoyed a few days ago.

Maybe you’ve even known for a couple weeks that you’re pregnant, but you went ahead and toasted the bride and groom at a recent wedding because your friend told you small amounts of alcohol so early in pregnancy don’t do any harm.

Whatever the case, you’re now worried and want to know what damage, if any, drinking in very early pregnancy can do.

First off, take a deep breath and let go of any guilt or shame that you feel about the past. You’re in a no-judgement zone here. Next, continue reading to learn what the side effects can be — and most importantly, what you can do to ensure good health for you and your baby moving forward.

At the very top of its alcohol and pregnancy information sheet — and in bold type, no less — the Centers for Disease Control and Prevention (CDC) advises that women who are trying to become pregnant or could be pregnant shouldn’t drink.

Why? It’s not really about the harm done by what you drink before you’re even pregnant (though this may affect your ability to conceive). It’s that no amount of alcohol at any point in pregnancy has been absolutely proven to be safe.

Since you can be pregnant without knowing it, the CDC is covering the possibility that you’re in the earliest stages of pregnancy — 3 or 4 weeks, often even before your missed period. (Many people don’t know they’re pregnant until they’re already 4 to 6 weeks.)

Like the CDC in the United States, the NHS in the United Kingdom says that if you’re pregnant or planning to become pregnant, avoid alcohol.

Truly specific research around drinking alcohol in very early pregnancy is pretty tricky. That’s because it would be unethical to put together a study and actually request that any segment of the pregnant population do something (drink alcohol) known to cause harm even some of the time.

What we do have: research that looks at people who self-report alcohol use during pregnancy as well as some animal studies. We also have a lot of science backing our understanding of human development in the womb, including brain and central nervous system development starting at week 3 of pregnancy (right after implantation).

In one 2015 study done in mice, researchers gave the animals alcohol at 8 days gestation — roughly equivalent to the early fourth week in a human pregnancy. They found that the offspring of these mice had changes to their brain structure.

The results suggested that early alcohol exposure can alter DNA chemical processes. Embryonic stem cells that change as a result of the mother’s alcohol consumption early in pregnancy could even impact adult tissue later on.

To be a little Captain Obvious here, humans aren’t mice. There’s no way to know at this time if this effect happens in the same way in humans. It’s definitely worth further study, though.

On the other hand, a study published in 2013 looked at 5,628 women who self-reported various amounts of alcohol consumption during early pregnancy. (For the purposes of this study, though, “early” meant all the way up until 15 weeks.)

Researchers looked for common effects of alcohol on pregnancy:

  • low birth weight
  • high maternal blood pressure
  • preeclampsia
  • smaller-than-expected size for gestational age
  • pre-term birth

They didn’t find a strong correlation between drinking early in pregnancy and an increased likelihood of these complications, so some people take this to mean it’s A-OK. But this study only looked at short-term outcomes (not long-term effects that might not show up until childhood) and not fetal alcohol syndrome disorders (FASDs).

These studies represent two ends of the spectrum — one shows some scary possibilities about changed DNA, and the other suggests no ill effects. Most studies fall more in the murky middle, though.

For example, this 2014 study looked at 1,303 pregnant women in the United Kingdom and their alcohol consumption before pregnancy and during all three trimesters. Results suggested that drinking — even fewer than two drinks per week — in the first trimester increased risk of complications, like lower birth weight and pre-term birth.

And this research published in 2012 suggested that even light drinking in the early weeks could increase miscarriage risk, though the risk goes up with heavier drinking.

It might be accurate to look at all the information out there and say that very light drinking in very early pregnancy doesn’t always (or often) cause problems — but it could. And different people define “light” differently, adding to the confusion. So following CDC and NHS guidelines of no alcohol at any point is the safest option and the one that we recommend.

There are a couple big concerns with drinking early in pregnancy: miscarriage and fetal alcohol syndrome disorders.

It’s an incredibly difficult reality that miscarriages are as common as they are. And even if you do everything by the book, the highest risk of miscarriage is in the first trimester — and it often happens due to issues outside of your control (like chromosomal abnormalities).

Numerous reliable sources and studies (like the one we mentioned above) mention that alcohol use in the first trimester may increase miscarriage risk. Why this happens isn’t entirely clear.

The other big risk is FASDs. Symptoms include:

  • pre-term birth
  • low birth weight
  • neurological problems
  • behavioral problems that show up later in childhood
  • certain abnormal facial features (thin upper lip, small eyes, missing vertical crease between the nose and lips)
  • cognitive difficulties

Here’s something to remember: in-utero human development doesn’t happen all at once. It happens over a 40-week period (more or less, but you know what we mean) and there are many contributing factors.

And while drinking at any stage of pregnancy should be avoided, both the American College of Obstetricians and Gynecologists and the Royal College of Obstetricians and Gynaecologists say harm from having a little alcohol before you knew you were pregnant is unlikely.

So if you drank alcohol before you realized you were pregnant, the important thing is that you stop now. Your tiny human’s brain has a lot of development yet to go.

Take your daily prenatal vitamin, maintain a healthy diet, avoid undercooked meats and raw or high-mercury fish, and keep your prenatal appointments — these are all wonderful things you can do to promote your baby’s health.

And while we’re on the topic of those prenatal appointments — talk to your doctor candidly about your concerns and let them know that you had alcohol early on.

If you feel uncomfortable chatting with them about things that may affect your pregnancy, find a new doctor. Being able to speak honestly about your health and the health of your baby during pregnancy is crucial to having a healthy, happy nine months.