Weight gain in infants breastfed by mothers who take fluoxetine

Objective. Despite the manufacturer's recommendation that fluoxetine not be used by women while breastfeeding, many women choose to do so. There is li ttle information available in the literature to suggest that this practice is or is not safe. The purpose of this study was to examine weight gain in infants who are breastfed by mothers who take fluoxetine, compared with wei ght gain in infants who are breastfed by mothers who do not take any psycho therapeutic medication. A secondary goal was to assess the frequency of rep orted side effects in infants who are breastfed by mothers who take fluoxet ine. Methodology. A retrospective cohort study design was used. Subjects were id entified from an ongoing pregnancy outcome study conducted through the Cali fornia Teratogen Information Service and Clinical Research Program. A total of 64 women were interviewed who had taken fluoxetine during a pregnancy b etween the 1989 and 1997; 26 of these women breastfed their infants and con tinued to take the medication, and 38 breastfed their infants but did not t ake the medication. Postnatal weight gain was taken from pediatric records, and the frequency of side effects was measured by maternal response to the interview questionnaire. Results. Using linear regression analysis, the infants who were breastfed b y mothers taking fluoxetine demonstrated a growth curve significantly below that of infants who were breastfed by mothers who did not take the drug. T he average deficit in measurements taken between 2 weeks and 6 months of ag e was 392 g (95% confidence interval: -5, -780). Using a repeated measures analysis of covariance for those infants with more than one postnatal weigh t measurement available, the difference between the two groups was similar, similar to 1.2 standard deviations (P = .005). In response to interview qu estions regarding side effects, no mother who breastfed her infant while ta king fluoxetine reported any unusual symptoms that could be attributed to t he medication. Conclusions. These data do not suggest that women who breastfeed while taki ng fluoxetine are likely to note unusual behavior in their infants that the y consider related to use of the medication. However, although there was no excess of infants in the fluoxetine group with postnatal weight measuremen ts >2 standard deviations below the mean, these data indicate that breastfe eding while taking fluoxetine is associated with reduced growth that may be of clinical importance in situations in which infant weight gain is alread y of concern.