The study
The LIFE Study followed 501 US couples trying to conceive until a positive pregnancy test or for 12 cycles. At enrolment, researchers measured bisphenol A (BPA) and 14 phthalate metabolites in urine from both partners. Some metabolites measured in men were associated with a longer time to pregnancy. No statistically significant association was identified for BPA. Estimates accounted for factors including age, body mass index and smoking.
Why read it
The interesting feature is the design: exposures were measured before the outcome and in both partners. This offers a useful bridge between experimental research and human observations, although the substances and conditions differ. It also helps distinguish a couple-level outcome, time to pregnancy, from an individual hormone measurement.
Limits & open questions
This was an observational study: association does not establish causation. A single urine sample imperfectly captures variable exposures, and the numerous analyses were not adjusted for multiple comparisons. Hormonal measurements were unavailable. These 2014 results do not establish that any food or supplement improves or impairs fertility, and they do not provide individual clinical advice.