Selective serotonin reuptake inhibitors (SSRIs) transfer into breast milk to varying extents. Paroxetine is reported to have the lowest transfer into breast milk (weight-adjusted infant dose 1-3%). Fluoxetine transfers to a greater extent (weight-adjusted infant dose ≤ 14%) and its active metabolite, norfluoxetine, has a long half-life of one to two weeks and may accumulate in a breastfed infant. Data on citalopram (weight-adjusted infant dose approximately 5%) suggest that the relative infant dose of citalopram is intermediate between paroxetine and fluoxetine. Based on these data, paroxetine is the preferred SSRI in breastfeeding women.