Established Prescription Drugs
The FDA has a categorization of drug risk to the fetus that runs from "Category A" (safest) to "X" (known danger—don't use!):
Category A: Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is no evidence of a risk in later trimesters), and the possibility of fetal harm appears remote.
Category B: Either animal-reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of a risk in later trimesters).
Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.
Category D: There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).
Category X: Studies in animals or human beings have demonstrated fetal abnormalities, or there is evidence of fetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.
An example of a Category X drug is the extremely dangerous anti-acne drug Accutane, which is why women on it need reliable birth control and frequent pregnancy tests if there's any doubt.
Keep in mind that the FDA classifications are very general classifications of very complex interactions between drug, patient, and fetus. They are general guidelines for your doctor and shouldn't be the final say on whether you and your baby are safe. For example, giving a Category C drug to a woman with epilepsy may seem more risky than giving a Category B drug; but if the B drug isn't as effective in controlling seizures, then failure of that drug may force her doctor to use a Category D drug as a rescue.
Using drugs for uses for which they haven't been officially approved
This is called "off-label" use of legitimate drugs. This is not only safe when overseen responsibly by a physician, it's even desirable in many instances. A perfect example of this was the use of Ritodrine for preterm labor. Normally a drug for asthma, it had the same effect on asthma, but also on preterm labor, as another drug, Terbutaline. Both controlled preterm labor and Ritodrine was FDA-approved for this, but Terbutaline wasn't. Terbutaline, however, was ten times cheaper, so it was the one used.
Medicine is an art as well as a science. For particularly troubling conditions in pregnancy, an obstetrician may choose to use a safely established drug in ways for which it wasn't originally designed. This isn't malpractice—it's the art of medicine. The best doctors will think creatively within their art, but then use the science to steer them away from doing any harm.
BOTTOM LINE: Prescription drugs are controlled (that is, the prescription itself) for a reason. These are substances that the government wants dispensed by way of knowledgeable individuals (doctors and pharmacists).
Once again, we're at the mercy of time and the marketplace. Most OTC medicines have been grandfathered into a safe spot in pregnancy. Antacids, laxatives, simple pain medicines, antihistamines, decongestants, and other common remedies are usually safe when they've stood the medical and legal test of time by earning a place on the shelf that any non-medically trained person can choose from. The label will say if a physician should OK it, but this is probably more of legal precaution for the company than a warning of any pending harm.
This is not to say that you should take anything off the shelf with reckless abandon. Combining several of these medicines, staying on any for an unreasonable amount of time, or exceeding the recommended dosage should prompt you to clear this with your obstetrician.
BOTTOM LINE: Most OTC medicines, used according to the directions, are safe. Any alterations in the labeled recommendations should be cleared.
The Rest of the World
Everything else in the world that could be a problem for a developing baby falls into a murky area. Power lines, computer monitors, cell phones, hair dyes, tanning booths, ultrasound (and the list goes on) have all been questioned. The problem is that our technology is advancing at an exponential rate, with truly new things bumping into pregnancy all the time. New pesticides for crops, factory emissions, microwaves—move over. It's a brave, new world, and it just keeps getting busier.
A patient once asked me if using NutraSweet could cause deformities in her baby. Besides telling her no, I also answered that just living in Louisiana was more likely to cause problems in her developing baby than a sweetener used by millions of pregnant women every day. The point here is that you have to live. If you avoided every possible thing that could possibly result in harm, you would never leave the house, unless you were running for your life from toxic mold and radon. Lighten up a little and keep your eyes and ears open to legitimate news items that apply to pregnancy.
Cosmetics, perms, and hair dyes are always a popular worry. The correct answer is that one should minimize exposure to chemicals that aren't necessary to be safe. The reality is that how I define "necessary" and how someone else does may be two different things. For the record, in my twenty-two years of private practice, I've never seen a cosmetic injury to a baby.
Tanning beds—harmless to baby, bad for your skin. Your skin's already stretched, so adding UV thermal injury and dehydration won't help.
BOTTOM LINE: Use common sense; a good rule is that anything that can hurt you may hurt your baby. Items of widespread use which are time-honored without any haunting legacies of horror stories are probably OK, but your doctor will stand by the advice that you should limit unnecessary exposure to chemicals.
Typically, it takes a lot more than an occasional glass of wine to make us obstetricians worry. But since the fetal-alcohol syndrome is so serious, I and all other obstetricians stand by the literature in stating that a safe amount of alcohol has never been officially established.
BOTTOM LINE: Pass on this one until you've finished breastfeeding.
Don't get me started! Cigarette smoke has over 2,000 chemicals in it. A known poison for your developing baby, each puff constricts nourishment to him or her. Each puff! Every single one. Quit. And if you fail, quit over and over again. Cigarettes are possibly more dangerous than cocaine, but don't do that, either.
BOTTOM LINE: Are you crazy?