Back in the mid-’80s, reports started to spread that a certain brand of cough syrup (yes, it’s Robitussin) could help improve fertility.
The thought was that this expectorant — originally engineered to help loosen and thin mucus in the lungs — could also have an effect on mucus a little lower down, in the cervix. One of the active ingredients in the cough medicine, called guaifenesin, helps liquefy mucus in your lungs, so you can cough it up and out of your body.
But it also theoretically works on other mucous membranes, including your cervix, which in turn would make it easier for sperm to travel through to fertilize an egg. Unfortunately, though, there’s been no clinical evidence that the drug can help you conceive any more quickly.
It probably can’t hurt (though too much unnecessary medication is never a good thing), but it’s likely that any success you have will be more due to coincidence than the medication itself.