Objective: To investigate the usefulness of the milk-to-plasma (M/P) ratio for assessing the risks for the breastfed infant associated with the maternal use of SSRIs.
Data sources: Medline, Toxnet, Embase, Current Contents, and PsycInfo indexed articles from 1980 to September 2006.
Study selection and data extraction: All studies reporting the M/P ratio in mothers taking SSRIs while breastfeeding or studies which such an information could be calculated from data reported in the article.
Data synthesis: Higher M/P ratios were rarely associated with a clinically significant impact on the babies during the early phases of breastfeeding.
Conclusions: So far no evidence-based information seems to support the hypothesis that SSRIs characterized by a M/P ratio <1.0 should be preferred. Hence, physicians should consider different parameters when attempting to choose the safest SSRI for the breastfeeding woman. These parameters might be represented by the number of well-documented published adverse event reports and the tendency of each SSRI of inducing in the infants serum concentrations that are elevated above 10% of average maternal serum levels. In any case, if the mother wishes to breastfeed her infant while taking a SSRI, the baby should be closely monitored in order to promptly detect any iatrogenic event.