We aim to determine the prevalence of self prescribing behaviour during pregnancy and its characteristics. For this purpose, we designed a cross sectional study and interviewed 400 pregnant women who had their prenatal care at Instituto Nacional Materno Perinatal, Lima. We found that 10.5% of the patients (42 patients) had a self prescribing behavior during pregnancy, 64.5% think that self prescribing behavior can produce congenital malformations. The medications used were classified as type A and B according to the Food and Drug Administration (FDA). Paracetamol was used more frequently (47.6%) followed by amoxicillin (16.7%). All the women who self-prescribed have had this behavior before pregnancy. According to these results, we conclude there is a low prevalence of self-prescribing behavior during pregnancy compared to the international literature.