Background: Breastfeeding has many short-term and long-term health benefits for infants. Short-term benefits include protection against childhood infections and mortality in low-income countries. The adult long-term effects usually emphasized are a reduction of excess weight and type 2 diabetes. However, there is a lack of available data on the impact of having been breastfed on adult fertility. Indeed, infertility probably has a multifactorial origin, including an environmental origin. The aim of this study was to investigate whether having been breastfed could be associated with unexplained infertility. Materials and Methods: This research is an ancillary study of the case-control study ALIFERT, for which both fertile and infertile couples were recruited. Breastfeeding statuses, collected from childhood health records, were compared among fertile and infertile individuals. Anthropometrics parameters were also used for analysis. Results: About 65.6% of infertile women and 63.3% of fertile women were breastfed, and 69% of infertile men and 67.4% of fertile men were breastfed. There was no statistically significant difference between fertile and infertile groups. Nevertheless, infertile women who were not breastfed had a significantly higher body mass index than those who were breastfed (25.8 kg/m2 vs. 23.2 kg/m2). Conclusion: In our study, we did not observe any association between having been breastfed and fertility in adulthood. However, we observed that, in infertile women, having not been breastfed may influence weight in adulthood. Trial registration: NCT01093378 ALIFERT. Registered: March 25, 2010.