Which robitussin help our cervical mucus? Need Help!?

Robitussin, the cough syrup can help thin the cervical mucus, that it claimed by a lot of women and reliable website such as babycenter and it it also recommended by a lot of doctors. By thining the musuc, sperm will swim easily and this eventaully increase the chance of conception. But this however only helpful to women that have poor cervical mucus. Am i right? ( A lot of women asked this before, you may browse, but sadly a lot of answeres called them idiot. For those of you who think this idea is idiot, please get the fact right first. I am kind of piss up with people that always called others idiot when actually he/she is!!) Okay back to my question. So my question is, which type or robitussin it is? I saw three diff types of it : Robitusssin DM, Robitussin SP and Robitussin. I am suppose to choose the Robitussin but the label does not mention guaifenesin. Am i missing other types?