You have probably been told that no medications are the safest medications during pregnancy. On the other hand, nine months is a long time to avoid a common cold with the annoying symptoms of sore throat, cough, congestion or fever. Studies suggest that over 90 percent of pregnant women will use an over-the-counter (OTC) cough or cold medication.  Is it safe? Which OTCs are safest? What about a simple cough drop?
Menthol is the most common active ingredient in cough drops. Menthol may sooth a scratchy or sore throat, but it is one of the least studied OTCs in humans or animals. It has never been assigned a pregnancy risk category by the Food and Drug Administration (FDA). That being said, there have never been any reports of adverse effects on pregnancy from menthol, so it is very likely to be harmless. [1-3]
Cough drops can include a lot of other active ingredients. These include benzocaine, vitamin C, eucalyptus oil, zinc, the cough suppressant dextromethorphan, and echinacea. None of these has been linked to problems in pregnancy.  There is some evidence that echinacea, zinc, and vitamin C may improve your ability to fight off a cold or shorten the duration of a cold. 
Some cough drops contain additional herbal ingredients like thyme, sage, peppermint, lemon balm, and mallow. Although there is no evidence these are harmful, there is also no evidence they add any benefit. Stay away from cough drops with elderflower, horehound, and hyssop. These herbs may cause uterine contractions. 
Bottom line on cough drops is read the labels and stick to the safest options. These include major brands like Halls, Vicks, Cepacol, Sucrets, and Luden. 
Cough and Cold OTCs
OTC cough and cold meds can be confusing because there are so many options. Many contain multiple classes of medication. Some of them include up to five active ingredients. However, when you break the ingredients down for safety, there are just five basic classes you need to know about. They are analgesics, dextromethorphan, guaifenesin, decongestants, and antihistamines. 
Analgesics reduce pain and fever.
- Acetaminophen is the most commonly used during pregnancy and the most studied. It is considered safe any time during pregnancy. [1,2]
- Nonsteroidal anti-inflammatory drugs (NSAIDs) found in OTC cold meds commonly include ibuprofen or naproxen. NSAIDs are considered safe during the first two trimesters of pregnancy. In the third trimester, some studies suggest a small increased risk for decreased amniotic fluid and possible heart problems in babies. The FDA says the risk outweighs any benefit in the third trimester. 
- Acetylsalicylic acid (aspirin) is also an NSAID, but it should be considered separately because it should be avoided any time during pregnancy. Aspirin in doses over 150 milligrams has been linked to bleeding problems in babies, possible birth defects, and prolonged labor. [1,2]
Dextromethorphan is a cough suppressant. This drug can be used to suppress a nagging cough that keeps you up at night, but you should remember that coughing is important to clear mucous from your lungs. There have been enough studies to say that this drug is safe throughout pregnancy. 
Guaifenesin is an expectorant. It thins out mucous making it easier to clear from your lungs or sinuses. There have been enough studies to say that this drug is safe throughout pregnancy. 
Decongestants include oral medications and nasal sprays. The two oral decongestants in OTC cough and cold meds are pseudoephedrine and phenylephrine. Use of oral decongestants in the first trimester may slightly increase the risk of birth defects according to some studies, although other studies have not confirmed this risk. Later in pregnancy, these drugs are considered safe, but you should avoid them in the first trimester. [1,2]
Decongestant nasal sprays have not been linked to any birth defects. They do not get absorbed into your blood so they are probably safer than oral decongestants. However, you should never use them for more than a few days, because they have a rebound effect that can make nasal congestion worse. 
Antihistamines dry up watery mucous secretions, like a runny nose. Common examples are diphenhydramine and chlorpheniramine. These medications are safe to use during early pregnancy, although they may make you drowsy. They may be taken at night to help you fall asleep. There is some risk of uterine contractions caused by high doses of antihistamine, so you should avoid these drugs in the last two weeks of pregnancy. 
Bottom Line on OTC Cough and Cold Meds
Avoid aspirin during all of your pregnancy. Avoid oral decongestants in the third trimester. Avoid antihistamines in the last two weeks of pregnancy. Other OTC cough and cold meds are relatively safe in pregnancy. On the other hand, the old saying that no meds are best still stands. [1,2]
You can certainly take acetaminophen for fever and pain due to a cold. Other than that, there is not a lot of evidence that any of the other OTC cough and cold meds are very effective at treating a cold. Resting, drinking lots of fluids, and using a vaporizer or a saline nose spray may be all you need. 
If you have any underlying health problems like high blood pressure, lung, or heart problems, talk to your pregnancy care provider before taking any OTC cough and cold preparation. Call your provider if you have a fever over 101.5 degrees or if you have cold symptoms for more than seven days. 
- S. Pharmacist, Pregnancy and OTC Cough, Cold, and Analgesic Preparations.
- Canadian Family Physician, Treating the common cold during pregnancy, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2377219/
- Pregnancy Related, Cough Drops While Pregnant, http://www.pregnancyrelated.com/cough-drops-while-pregnant/