1. Department of Clinical Sciences and Community Health University of Milan Milan Italy
2. Infertility Unit Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico Milan Italy
3. Department of Statistics and Quantitative Methods, Unit of Biostatistics, Epidemiology and Public Health University of Milano‐Bicocca Milan Italy
4. National Center for Healthcare Research and Pharmacoepidemiology Milan Italy
5. Department of Woman, Newborn and Child Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Milan Italy