If you were to guess based on TV and movies, baby-making typically includes some R&B slow jams and a few glasses of wine. Unfortunately, this could be bad for the baby, as new research has prompted one expert to recommend that aspiring dads lay off of the booze for 90 days before they attempt to conceive.

It’s common knowledge that drinking alcohol while pregnant can pose a risk to the developing fetus. But most people, including fertility experts, thought for a long time that dad could crack a beer before conception and it wouldn’t have much of an effect on his baby. And when Michael Golding, Ph.D., a veterinary researcher at Texas A&M University, began to look into if it could, he faced a lot of pushback.

Golding was discouraged from looking at the impact paternal drinking has on conception and child development — even in animals — mostly by academics who were stubbornly steadfast that alcohol-related birth defects were the mother’s fault. It didn’t help that the Surgeon General had been warning women not to drink if they were considering pregnancy since the early 1980s but never encouraged the same caution for dads.

“People would completely dismiss this idea while simultaneously acknowledging that no one had ever looked,” Golding says.

In short, fetal alcohol syndrome (FAS) — a condition caused by prenatal alcohol exposure that can result in a low birthweight, facial abnormalities, a smaller head, hyperactivity, speech and learning problems, and other issues — was blamed squarely on mothers. Even when moms denied drinking, scientists assumed that they were lying about their alcohol use.

But finally, researchers are looking to dads.

Last spring, Golding and his colleagues demonstrated using mouse models that when males consume alcohol prior to conception, they can cause brain and facial growth defects in their baby that are associated with FAS. The findings were published in The Journal of Clinical Investigation in April 2023.

Moreover, Golding’s findings indicate that paternal alcohol exposure has an even stronger effect on facial deformities than maternal exposures in mice.

“We’ve found that these paternal alcohol exposures have a pretty profound impact on the placenta,” which could cause problems with craniofacial differences and other issues with development, Golding explains.

Or at least that’s the case in mice, which are the standard for genetic research in universities across the country. Humans and mice are both mammals and are considered similar genetically by scientists’ standards. Mice are also useful in research like Golding’s because his team can control their sleep, diet, environment, and even how much genetic variation there is between mice in a study.

The mechanism by which dad’s drinking could affect baby’s development is through epigenetics, or how environment and behaviors like alcohol consumption changes to what extent genes are turned off or on — in this case, in the dad’s sperm, which becomes half of the genetic material for his baby.

Three months are what it takes to recover from alcohol withdrawal.

After his April 2023 study that linked FAS facial features to paternal alcohol use in mice, Golding and his team hypothesized that alcohol was directly messing up sperm during its formation. Sperm formation takes about 35 days in mice, so they thought that if they stopped exposing the males to alcohol about a month before conception, their offspring would be healthy.

But in a recent follow-up study, again in mice, that wasn’t the case. After a month of sobriety, the males still produced offspring with FAS qualities. This suggests that the effects of alcohol continue damaging sperm for some time even after the mice get sober.

How could that happen? Obviously, the alcohol couldn’t be affecting the sperm directly. Rather, Golding’s team found evidence of oxidative stress in sperm and the male reproductive tract for about a month after exposure to alcohol ceased, as they were going through withdrawal.

Oxidative stress is caused by an overabundance of highly reactive molecules called free radicals that and is known to harm the male reproductive system. In the mice, it was the main driver of epigenetic changes in the sperm. So the mice wouldn’t be able to start making healthy sperm again until they finished going through withdrawal.

It doesn’t take a lot of drinking for this withdrawal and oxidative stress to occur, either. Golding’s mice models revealed that the equivalent of three to four beers a few days a week were enough to cause oxidative stress for a month.

In humans, it takes about 21 days to a month of abstinence from alcohol to finish going through withdrawal and recover from oxidative stress. Then, it takes about another 71 to 74 days to make and mature new sperm. So, it would take about 92 to 100 days for a newly sober dad to have healthy sperm ready to make a baby, Golding says.

However, based on the evidence, he doesn’t think the earliest phases of sperm production are impacted in casual drinkers, so he says three months is a “solid estimate” for how long dads should stop drinking before trying to conceive, although his team still needs to test this assumption with their mouse model.

How researchers will make the leap from mice to humans.

It’s worth reiterating that these experiments are limited to mice, but this type of genetic research is often done in model organisms and translated to advice for humans.

Additionally, human studies have suggested that the more fathers drank preconception, the more their children struggled with behavioral problems. So there is evidence in humans that epigenetic changes to sperm from alcohol consumption are at play.

Reproductive endocrinologist John Norian, M.D., notes that many human studies are limited by self-reporting, and some men not being entirely honest about how much they’re drinking. This means the impact of a father’s drinking prior to conception could be even stronger than what we know (and is another reason to use mouse models, in which alcohol amounts can be controlled).

But when advising couples at the HRC fertility, a network of fertility clinics throughout California, Norian is less alarmist and more practical with his abstinence recommendations for dads.

“I ask men [who are trying to conceive] to avoid alcohol four to five days a week, to keep it at a minimum when out with friends or family, and not to overdo it,” Norian says. “By stopping or severely reducing alcohol consumption, a man may improve their sperm health.”

He also agrees that it can take three months of limiting alcohol or more to see an improvement in sperm health.

To that point, Golding suspects that men who drink a maximum of one or two drinks a week might be able to get this preconception guideline down closer to 60 days because evidence of prolonged oxidative stress was more noteworthy at the three-drink mark and above. But more research needs to be done for him to have full confidence in that recommendation.

“Until we understand how alcohol is inducing these effects, the safe bet is still three months,” Golding says.