Do Antibiotics Decrease Fertility?

Is there any data on the impact of antibiotics on fertility or chances of conception? Context: I have regular urinary tract infections and, despite all best efforts, sometimes need to take antibiotics (usually nitrofurantoin), usually related to sex during the ovulation window. I know such antibiotics are safe during pregnancy but am keen to know if they impact our conception chances.

—UTIs are the worst

UTIs are the worst. I also used to get them all the time, pre-children. (The first time, in college, I didn’t know what was going on, and I got to the point of peeing blood before my best friend, Tricia, was like, “Yeah, that’s a UTI, let’s get you to the doctor.” I digress.) Interestingly, I’ve gotten them much less post-children, so perhaps you will be as lucky.

In terms of conception chances, the best data we have on this is from a study done in Denmark in 2023. The study followed about 9,500 women trying to conceive and surveyed them every eight weeks over the course of a year about conception success. The researchers linked these data with a database that showed what prescriptions people filled. They could then estimate whether the women who filled antibiotic prescriptions were less likely to get pregnant.

A significant limitation of this method is that they would not be able to separate out the impact of being ill from the impact of the treatment. Useful for you, though, is that they do estimate the impact separately for women who have UTIs as the reason for the antibiotic usage.

What they find is that, overall, those who use antibiotics have slightly lower conception rates than those who do not — on average, about a 14% reduction. Very important: when they limit to people who have UTI as the treatment reason, they do not find any reduction in fertility.

The combination of the likely confounding with illness and the reassuring findings on UTI treatment means my best read of the data is that there is little reason to think your fertility would be impacted by this treatment.

Remember to pee after sex!