The Mediterranean diet represents one of the most studied dietary patterns, however, there is no single tool for measuring the grade of adherence and no single criteria to adapting these indices to pregnant women. We characterized the adherence to the Mediterranean diet (MDA) of pregnant women participating in the NELA cohort and identified the sociodemographic determinants and lifestyle habits associated with a higher risk of a low MDA. Maternal diet during gestation was assessed by a validated Food Frequency Questionnaire (FFQ) (n=665). We estimated Relative Mediterranean Diet score (rMED), Alternative Mediterranean Diet score (aMED) and Alternate Healthy Index-2010 (AHEI-2010). Multivariate regression models were performed to identify the sociodemographic and lifestyle factors associated to each index. Mothers with lower age and more previous deliveries had a greater probability of low MDA (P <0.05). Only, for aMED index, mothers with university education and / or who practiced 2 or more hours per week sport activities had a lower probability of a low MDA (P <0.01). These results may be useful in order to design intervention strategies and dietary recommendation for pregnant women.