The prevention of relapses and the treatment of depression during pregnancy are difficult challenges. The maintenance of antidepressants in pregnancy with its concomitant risks to mother and child needs to be weighed against those associated with not treating the disease. This study aimed at quantifying the impact of the occurrence of pregnancy on the course of antidepressant treatment among newly treated women (< 6 months). We performed a comparative observational cohort study using the nationwide French reimbursement healthcare system database. Women who conceived in 2014 and initiated an antidepressant at any time in the 6 months before pregnancy were compared with nonpregnant women newly exposed to antidepressants with matching on age, antidepressant exposure, history of psychiatric disorders, and area of residence. The primary outcome was a composite of antidepressant discontinuation, switch to another antidepressant, and concomitant use of antidepressants. The secondary outcome was the resumption of antidepressant during follow-up. We used Cox marginal proportional hazards models to compare time to outcomes between pregnant and nonpregnant women. The pregnant cohort included 6593 women, and the comparison cohort 29,347 nonpregnant women. In the period following the first month of treatment, pregnant women were more likely to experience treatment modification, and especially to stop receiving it, compared with nonpregnant women (adjusted hazard ratio (aHR) 1.58; 95%CI, 1.51–1.62). Pregnant women who discontinued treatment had a 41% decreased incidence of antidepressant resumption compared with nonpregnant women (aHR 0.59; 95%CI, 0.56–0.62). Pregnancy was a determinant of antidepressant treatment modification, and especially of discontinuation.< Réduire