Socioeconomic disadvantage can be harmful for mother's health and can influence child's health long term. The aim of this study is to analyse social inequalities between pregnant women from four INMA (INfancia y Medio Ambiente) cohorts. The analysis included 2,607 pregnant women recruited between 2004 and 2008 from four INMA cohorts. Data on maternal characteristics were collected through two questionnaires completed in the first and third trimester of pregnancy. The relationship between socioeconomic status (SES) and maternal health, dietary intake, lifestyle habits and self-care related variables was modelled using logistic regression analysis. 33.5 % of women had a university level of education and 47 % had high occupational class. Women with higher SES reported healthier habits, fewer complications during pregnancy, better weight gain control and attended more prenatal appointments than women with lower SES. The risk of sedentary behaviour and passive smoking was higher among women with a lower level of education (OR = 1.7, 95 % CI 1.3-2.2 and OR = 1.6, 95 % CI 1.2-2.3, respectively) and with less skilled occupations (OR = 1.7, 95 % CI 1.4-2.0 and OR = 1.2, 95 % CI 1.0-1.5, respectively). Although both SES indicators-occupation and education-act as social determinants of diet, occupation was a more powerful determinant than education. For other lifestyle and self-caring variables, education was a more powerful predictor than occupation. Social inequalities were observed in health, habits and self-care during pregnancy. Proper care during pregnancy requires the control of common clinical variables and the knowledge of socioeconomic conditions of the pregnant women.