ObjectivesTo explore health-related lifestyles in women before and during pregnancy, and to determine the potential differences between both and the relevant factors. Materials and methodsA cross-sectional observational study including 348 women with a child <5 years of age was conducted in six health areas. The following variables were recorded: sociodemographic (age, educational level, marital status, social class, type of cohabitation, nationality), health-related habits (physical activity, diet, tobacco use, alcohol consumption), health conditions, and medication intake. ResultsFour lifestyle habits were compared between the pre-conception and pregnancy periods: diet, physical activity, and alcohol and tobacco use. The proportion of women who consumed alcohol (42.8 % vs 3.4 %) or smoked (19.3 % vs 12.4 %) was significantly higher before conception (p < 0.01). Conversely, the proportion of inactive women was lower before pregnancy, with 23.3 % (CI95%: 18.7–27.9) formerly classified as active versus 35.3 % (CI95%: 30.2–40.5) (p < 0.01). Similarly, adherence to the Mediterranean diet increased during pregnancy (62.9 % vs 75.0 %; p < 0.01). Furthermore, 53.2 % (CI95%: 47.8–58.5) of women reported a change from non-healthy to healthy in at least one of the evaluated habits. Logistic regression analyses revealed the variables associated with a positive change, which were being national Spanish (OR: 6.9) and experiencing the first pregnancy (OR: 1.8). ConclusionsThe lifestyles of women undergo changes between the pre-gestation and pregnancy periods. However, such variations do not affect all health-related habits similarly. A positive change was observed in diet, alcohol consumption, and smoking habit, whereas pregnancy negatively impacted on physical activity and sedentary behaviours.