ImportanceSelective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are consistently reported to be discontinued by approximately half of pregnant women. Little is known about how this may be associated with postpartum psychiatric health.ObjectiveTo investigate associations of SSRI or SNRI discontinuation in pregnant women with depression or anxiety and psychiatric health and sick leave absence after childbirth.Design, Setting, and ParticipantsThis population-based cohort study was conducted between 2006 and 2019 using data from Swedish population-based registers. Pregnant women with a filled prescription of an SSRI or SNRI in the 90 days before pregnancy without recorded comorbid or severe psychiatric conditions were included. Analyses were performed in November 2023.ExposuresK-means for longitudinal data was used to cluster trajectories of SSRI and SNRI use during pregnancy, resulting in 2 trajectory groups based on the number of days covered, defined as continued and discontinued use groups.Main Outcomes and MeasuresThe primary outcome was psychiatric-related hospitalizations by 90 days after childbirth. Secondary outcomes included psychiatric-related outpatient visits, self-harm and suicide, and any-cause mortality by 90 days after childbirth and all outcomes plus sick leave absence by 1.5 years after childbirth.ResultsAmong 27 773 pregnant women (17 241 aged ≥30 years [62.1%] at childbirth), 13 184 women (47.5%) had discontinued SSRI or SNRI use and 14 589 individuals (52.5%) had continued use. Individuals in the discontinued compared with continued use group were younger (5588 women [42.4%] vs 4944 women [33.9%] aged <30 years), less educated (4281 women [32.5%] vs 5821 women [39.9%] who completed postsecondary education or above), and more likely to have smoked in early pregnancy (1445 individuals [11.0%] vs 1180 individuals [8.1%]), been born in a non-Nordic country (1641 individuals [12.4%] vs 975 individuals [6.7%]), and used anxiolytics (1301 individuals [9.9%] vs 1119 individuals [7.7%]) and hypnotics and sedatives (1609 individuals [12.2%] vs 1510 individuals [10.4%]). Psychiatric-related hospitalizations occurred in 49 individuals (0.4%) in the discontinued vs 59 individuals (0.5%) in the continued use group in the 90 days after childbirth, with an adjusted hazard ratio (aHR) of 1.28 (95% CI, 0.85-1.91), while at 1.5 years after childbirth, the aHR was 0.81 (95% CI, 0.66-1.00). Lower hazard rates for psychiatric-related outpatient visits in the discontinued vs continued use group at 90 days (aHR, 0.59; 95% CI, 0.53-0.66) and 1.5 years (aHR, 0.60; 95% CI, 0.57-0.64) after childbirth were found. No difference in sick leave absence was found; however, individuals who discontinued had fewer days of sick leave by 1.5 years after childbirth than those who continued (mean [SD], 44.6 [70.6] days vs 53.1 [82.3] days).Conclusions and RelevanceIn this study, approximately half of pregnant women discontinued SSRIs or SNRIs, and discontinuation during pregnancy was not associated with adverse psychiatric-related outcomes, including hospitalizations, outpatient visits, suicidal behavior, or sick leave absence in the 90 days or 1.5 years after childbirth.