Footnotes

• Contributors BM coordinated the collection and analysis of data and drafted the work; EP gave substantial contribution to the interpretation of possible shared mechanisms of fetal damage of the two substances; GC analysed data on fetal adverse outcomes; RD’A monitored the study method and statistical analysis; PT coordinated the Study Group. All the five authors contributed to the conception and design of the main study, accurately revised the text of the letter and approved it.

• Funding This study is part of a project funded by the Italian Ministry of Health-Research Program RF 2010-2315893.

• Competing interests None declared.

• Ethics approval Local Ethics Committee (21/2/2013) and Hospital Management Executive (determination 464, 13/3/2013)

• Provenance and peer review Not commissioned; externally peer reviewed.

• Collaborators ESPEA Study Group members: Gabriele Accetta¹, Gianni Astolfi², Sergio Battaglia³, Francesca Bisulli¹,⁴, Guido Cocchi⁵, Letizia Conti⁵, Alessandra Curti⁶, Roberto D’Alessandro¹, Camilla Lupi³, Barbara Mostacci¹, Ilaria Naldi⁷, Carlo Piccinni⁷, Elisabetta Poluzzi⁷, Nicola Rizzo⁶, Giuliana Simonazzi⁶, Paolo Tinuper¹,⁴, Corrado Zenesini¹. ¹IRCCS Institute of Neurological Sciences of Bologna, Bologna, Italy; ²Registro IMER, AziendaOspedaliero-Universitaria di Ferrara, Ferrara, Italy; ³Regione Emilia Romagna SISePS, Italy; ⁴Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy; ⁵Department of Medical and Surgical Sciences DIMEC, Division of Prenatal Medicine, St. Orsola Malpighi Hospital, University of Bologna, Bologna, Italy; ⁶Department of Maternal and Paediatric Sciences, Neonatology, St. Orsola- Malpighi Hospital, University of Bologna, Bologna, Italy; ⁷Department of Medical and Surgical Sciences DIMEC, University of Bologna, Bologna, Italy.

• Correction notice Since this letter was first published online Paolo Tinuper’s affiliations have been updated so that he is also affiliated with the first institution.