In general, try not to take them.
As everybody knows, you’re not supposed to take any medication while you’re pregnant, or drugs/substances of any kind. Even over-the-counter medications like Tylenol have the standard advisory warning to ask your doctor about the medicine if you’re nursing or pregnant. This is because most (if not all) chemicals pass directly into a baby’s system from the mom, and we’re not sure how much they impact their sensitive development. A lot depends on the type of chemical, the amount, strength, or frequency, and any individual sensitivities involved. The medical establishment, fortunately, just does not conduct potentially dangerous studies on pregnant women and nursing babies. So we learn mostly from accidents, case studies, animal experiments, or good old logic.
Because the developing baby is the most precious time of that child’s life, healthwise, it makes sense to be extraordinarily careful with any chemicals you are around or ingesting. If you can avoid taking something, you should. That said, sometimes there are extenuating circumstances that drive moms to the drugstore for relief, or situations they cannot avoid taking medicine for (if they are diabetic, for example). Fortunately, history has shown that the majority of babies can be born “ok” under these types of medical circumstances. Only a handful of medicines have caused such devastation as the Thalidomide tragedy, and other chemical tragedies are associated with recreational drugs, substance abuse, or chronically unsafe working conditions. So rest easy if you took some Nyquil before you knew you were pregnant!
In general, you have a lot less risk with over-the-counter medications. That doesn’t mean you should just pop an Advil every time you get a headache. But a certain number of OTC medications like Tylenol, Pepto Bismol, Sudafed, and Robitussin have been generally approved for occasional use during pregnancy without alarm. I took some generic decongestants, including Dayquil and Tylenol Flu, a couple times while I was pregnant because I was hit hard with influenza for about seven days whenever I had a winter baby. Also I had a rotavirus once and needed to take Immodium for several days for safety’s sake. These types of occasional uses, in warranted conditions, can actually help your baby because they are helping you. Obviously the body calls for rest and fluids to self-medicate, but there are times when self-medication is difficult, too long, or too impractical to wait for on its own (especially when you have other small children at home to watch). Use your judgment and call your practitioner if you have questions when the sickness comes up.
For prescription drugs, I can’t say much. My midwife recommended Reglan to me when I was hyper-nauseous with my fourth child, past the first trimester. I had three other toddlers at home and was barely sleeping at night because my stomach ached so badly. After thirteen weeks of trying to withstand the pain, I caved and got the prescription. It worked immediately, so I used it for several months. The only side effect was that it made me sleepy, so I switched to double-strength Zantac in my seventh month, then to Pepto Bismol for my eighth. By my ninth, it was pretty much gone. I did what I had to do! (And the baby was born fine, with no health problems so far).
So do what your situation warrants, but always err on the side of caution. Try not to get pregnant if you’re on questionable drugs like Zoloft or Paxil, or have been on them within the past year. They can take awhile to exit the system and can effect the baby’s as well as your own body. Try not to get new vaccines, try new medications, or experiment with new regimens while you’re pregnant. Play it safe. The reality is that whatever you put into your body will affect your prenatal baby somehow, and probably even your nursing one. The question is to what extent and whether the benefits outweigh the costs. Many women side with the epidural, for example, or need the spinal for Caesarean sections, and they get them because the effects on the baby are limited in time and intensity. But babies can be born drunk, high, or otherwise intoxicated with whatever chemicals you took. And obviously there are risks of defects when the substance is dangerous.
But this post is for the normal moms out there afraid to take their Tums because they’ve got heartburn. Or who had their daily cup of caffeine for two months before they found out they were pregnant. Rest assured that it’s probably ok. I even drank Diet Coke throughout one pregnancy, against my conscience (but because I was so tired in the mornings from dealing with my firstborn, who was only six months old when I got pregnant). And my second born child is probably the most peaceful, laid-back, non-caffeinated baby you could ask for. He even slept through the night at six weeks old. So don’t freak out. Be smart but cool. Health is not your religion, but it is your responsibility. Especially when you’re pregnant. So do the wise, reasonable thing, and you’ll both turn out fine!