If your only sources of information were blog posts, Reddit, and community forums, you might be convinced that cough syrup medications like Mucinex or Robitussin are the magic secret to conceiving while you're ovulating. There are many people who are TTC posting stories of cough syrup making their cervical mucus more sperm-friendly, which then helped them conceive — like one TikTok user who recently went viral for claiming that it helped her get pregnant.
So, is the magic ingredient to conceiving hiding in your medicine cabinet? Short answer: no. According to experts, cough syrup medications like Mucinex or Robitussin do not significantly boost your chances of conceiving. Any “scientific” claims of cough syrup improving fertility are based on a single, small, methodologically flawed study done almost 40 years ago.
In this post, we’ll dive into the world of fertility and guaifenesin (the active ingredient in expectorants, decongestants, and cough syrup like Mucinex). We’ll dig up the scientific roots of this myth, review what the latest science says on cough syrup, ovulation, and conception, and highlight the practical takeaways for people who are trying to conceive.
Note: This article refers to Mucinex broadly, but is not the same thing as Mucinex D, which contains pseudoephedrine. That medicine should only be taken with a doctor's supervision, under any circumstances.
Why do people think Mucinex makes cervical mucus more fertile? Recapping the study on guaifenesin
Sometimes it’s hard to trace the roots of ideas in science. Luckily, this is not one of those times. All articles that reference any sort of scientific data supporting a relationship between cough syrup and your fertility point to a single study, published in 1982:
- Researchers tested the effect of taking guaifenesin (the main ingredient in medicine like Mucinex and Robitussin) during the fertile window and its impact on cervical mucus in opposite-sex couples that hadn’t gotten pregnant after 10 months of trying.
- They examined the cervix and cervical mucus two hours after sex, and looked at sperm motility as their main marker of “cervical mucus quality.” (If it seems strange to you that they looked at just one sperm-related variable to understand cervical mucus quality, you’re in good company).
- They found that “cervical mucus quality” significantly increased in 58% of the couples; slight or no improvements were observed among the rest. In 10 couples where infertility could be tied to cervical mucus (i.e., they couldn’t find any other issues), eight got pregnant after an average of 2.4 months on guaifenesin.
Sounds awesome, right? Not so fast. This study has some critical flaws that make it very difficult to confidently say there’s any real effect:
- Most importantly, there was no control group — meaning all study participants took guaifenesin. It’s entirely possible that the same rates of “cervical mucus quality” improvement and pregnancy would be observed among people not taking the drug, and if so, we’d conclude that the drug doesn’t have a meaningful effect on chances of conception. Without a control group, it’s impossible to estimate the added benefit of any sort of medication or intervention.
- This study also only focused on infertile couples and very few people were included in the study. A small sample and a specific cohort (infertile couples) means we cannot be confident we’d find the same thing in the general population.
- Based on our (very thorough!) search, there have been no published attempts to replicate the effect of cough syrup on conception or cervical mucus quality. And it’s not like Mucinex has any secret data on this that does show a relationship — they’ve gone on record saying that they don’t have any data on Mucinex and fertility or cervical mucus, and that they don’t recommend its use for this purpose. This means any “scientific” claims of cough syrup improving fertility are based on a single, small, methodologically flawed study done almost 40 years ago.
Why the myth about Mucinex + TTC gets perpetuated
While there’s no data showing cough syrup improves fertility, it’s easy to conjure up a story about why these two things could be related.
The “logic” behind the argument goes like this: Cough syrups work by thinning the mucus that lines your chest and throat, making it easier for the mucus to drain out. If cough syrup thins out mucus throughout the body, and thin cervical mucus is helpful for conception… then does cough syrup make cervical mucus thinner, therefore increasing your chances of conception?
The claim may sound “logical,” but we don’t have the data to back it up.
Cervical mucus changes at various stages of the menstrual cycle. Right before ovulation, cervical mucus production is at its peak, and is usually thin and stretchy (giving it the nickname “egg white” cervical mucus). “Egg white” cervical mucus is the most sperm-friendly; that is, relative to cervical mucus at other points in the cycle, it helps sperm move to the upper reproductive tract where it could potentially meet and fertilize an egg.
So why do people continue to try using cough syrup to increase their odds of getting pregnant? There are some anecdotal reports of people conceiving just a few months after taking cough syrup in their fertile window (though there’s an equal number of anecdotal reports saying the opposite), but anecdotal reports are no stand-in for rigorous science.
As Dr. Natalie Crawford, a reproductive endocrinologist, said in this recent article, “There is no conclusive help — or fertility doctors would be recommending it for everyone. That being said, it has a hypothetical mechanism of action that makes sense with very few risks — and it is inexpensive.”
Some doctors may also suggest that people try using cough syrup to boost their odds of conception not because they have any concrete data suggesting that it’ll help, but rather because there’s no reason to think it would hurt.
This advice changes when it comes to Mucinex D, or any meds with pseudoephedrine as an ingredient – those should not be taken without a doctor's supervision. In a Buzzfeed article, Dr. Crawford clarifies: "Mucinex and Guaifenesin with the 'D' component are not recommended and some people — especially those with high blood pressure — should not take this combination of medications."
The bottom line
The scientific evidence suggesting a link between cough syrup and conception is critically lacking, and the myth that they may be related can be traced back to one less-than-great study that’s never been replicated.
There aren’t any clear downsides to taking cough syrup in your fertile window, though there aren’t any clear upsides, either. Some people may think that something with no demonstrated negatives may be worth trying; others may think that something with no demonstrated positives may not be worth trying. This is completely a matter of personal preference, and there is no right or wrong answer here. It’s always best to talk through these decisions with your own doctor so you can make the one that is right for you.
That being said, if you have noted any irregularities with your cervical mucus, or meet the clinical definition of infertility (trying to conceive for more than 12 months if you’re under age 35, or for more than six months if you’re over age 35), we’d suggest skipping the mythical medical cabinet remedies and reaching out to a doctor.
This article was reviewed by Dr. Eduardo Hariton, an OB-GYN and reproductive endocrinology and infertility fellow at the University of California in San Francisco.