A glass of bubbly may actually be a safe way for an expectant mom to celebrate her pregnancy — and a few cups of coffee might not hurt either.

Much of the science behind the long litany of forbidden foods, drinks, and activities for pregnant women is bunk, according to economist and Wall Street Journal columnist Emily Oster. Her upcoming book Expecting Better: Why Convention Pregnancy Wisdom Is Wrong — and What You Really Need to Know turns a critical lens on the studies behind the rules and regulations imposed on pregnant women, and she's finding that most don't hold up to scrutiny.

"Being pregnant was a good deal like being a child again," she writes at the Journal. "There was always someone telling me what do." More troubling, though, was that "recommendations from books and medical associations were often vague and sometimes contradictory." Even worse, she says, the information tends to be alarmist and unfounded.

As a result, the medical community tends to assume fetal threats when they just aren't there, or at least aren't as dangerous as they are stated to be. "The key problem lies in separating correlation from causation," writes Oster. For example, women who drink more coffee tend to have higher rates of miscarriage, but the reasons they're drinking more coffee in the first place might play a more damaging role than the caffeine.

What are the big pregnancy taboos that Oster says you can put to rest?

Caffeine: As mentioned above, the command that pregnant women shall not enjoy a cup of java is unnecessary. In her article and book, Oster notes that few studies take into account the fact that women who drink more coffee also tend to be older, which is also tied to a higher likelihood of miscarriage. Furthermore, nausea is a sign that a woman's pregnancy is actually going well, and unsurprisingly, nauseous women choose not to drink coffee. Their pregnancies may be healthier regardless of the fact that they cut down on coffee.

Although some studies did suggest that consuming more than two cups of coffee a day led to a significantly higher rate of miscarriage, Oster evaluates the evidence and concludes, "It doesn't matter how much coffee you drink each day, as long as you consume less than your pre-pregnancy levels."

Alcohol: No libations is a biggie. Pregnant women in America are generally instructed to run away if a glass of Chardonnay comes within 100 yards of their uteruses. The stigma surrounding pregnant women drinking is not as high in Europe or Australia, which tends to produce studies showing that light drinking (up to one glass a day) makes no cognitive or behavioral difference on a baby.

Oster also addresses one popularly cited American study that claims even one drink can harm a baby. It turns out that 45 percent of the women in the study who had at least one drink also used cocaine, which could pretty obviously confound the results. Her ruling? "Drink like a European adult, not like a fraternity brother."

Deli meats: Less well-known in the non-pregnant community is the ban against foods associated with various pathogens, especially Listeria bacteria, which can cause late miscarriage and stillbirth. A 2013 list from the FDA of foods to avoid includes hot dogs, soft cheese, refrigerated pates or meat spreads, and refrigerated smoked seafood.

Oster's research shows that queso fresco and deli turkey show up frequently enough as Listeria sources to keep them out of the diet of pregnant women. However, she estimates that cutting out deli ham "would lower my risk from 1 in 8,333 to 1 in 8,255." So, there's no need to completely stifle your deli cravings.

Weight gain: Contrary to the popular image of pregnant women tossing back bon-bons, most women today are clearly instructed to watch their weight and gain no more than 25 to 35 pounds (and a lot less they if are overweight or obese). There is solid proof that if you gain less weight during pregnancy, your baby tends to be smaller, and if you gain more weight, your baby tends to be larger; both ends are associated with risks.

However, while larger babies tend to be associated with a more difficult delivery, smaller babies are associated with breathing difficulties and neurological issues. Thus, Oster suggests that you should actually be "more worried about gaining too little weight than too much."

Changing cat litter: Another under-the-radar but pervasive regulation on expectant moms is to not change kitty littler because it can be contaminated with toxoplasma from cats. Oster tells New York that this is "overblown — unless you have, like, three kittens in your house that are living outside and eating raw meat." However, there is a decent likelihood of being exposed to this parasite through gardening because, as Oster explains, "There are potentially more cats living in your yard than in your house."

But not everyone is ready to toast the new pregnancy manual, especially doctors. Alcohol consumption in particular is a pregnancy ban that the medical community is unwilling to relax. Dr. Donnica Moore tells ABC that, "There is no amount of alcohol in pregnancies that should be considered safe. Anything that the mother ingest flows through the placenta and blood stream to the fetus."

And Dr. Jennifer Ashton tells ABC that she disagrees with Oster's strictly analytical approach to pregnancy guidelines. "In general, it's very important for people to understand there's a lot more to practicing medicine than crunching numbers."

Even outside of medical professionals, there are skeptics of Oster's more laissez faire approach to pregnancy. "There are definitely still questions about what's safe and what's not," writes Melanie Abrahams, a senior editor at Parents, but "why take the risks?" She feels that too often Oster relies on an "'it worked for me' approach," and that some of her claims are a "flat-out danger to pregnant women and their families."

Ouch. Strong words, but this logic may win the hearts, if not the minds, of pregnant women. When it comes to something as sensitive and nerve-racking as pregnancy, more expectant mothers may side with the "why risk it?" reasoning.

Then again, Oster makes a compelling case for encouraging women to "assess risks for themselves" and to reject "categorical limits based on fuzzy science and half-baked research." If her book becomes a bestseller, it may just be a matter of time before champagne becomes standard fare at baby showers.