New mothers who are taking a common class of antidepressants may have a delay in lactation and need extra support to breastfeed, researchers say.

The selective serotonin reuptake inhibitors or SSRI type of antidepressants such as Prozac and Paxil may be linked with a delay in the start of full milk secretion, according to a study to be published in the February issue of the Journal of Clinical Endocrinology & Metabolism.

The body's production and regulation of the hormone serotonin is closely related to the ability of the breasts to secrete milk at the right time, said study co-author Nelson Horseman of the University of Cincinnati.

While SSRI drugs can affect mood, emotion and sleep, "they may also impact serotonin regulation in the breast, placing new mothers at greater risk of a delay in the establishment of a full milk supply," he said in a release.

'More human research is needed before we can make specific recommendations regarding SSRI use during breastfeeding.'—Study co-author Nelson Horseman

In the study, researchers looked at the effects of SSRI on milk production in 431 new mothers.

The average onset of lactation was 85.8 hours postpartum for the SSRI-treated mothers and 69.1 hours for mothers not treated with SSRI drugs, the team found. They defined a delay as 72 hours after the birth.

'Very helpful medications'

"SSRI drugs are very helpful medications for many moms, so understanding and ameliorating difficulties moms experience can help them achieve their goals for breastfeeding their babies," said Horseman.

"More human research is needed before we can make specific recommendations regarding SSRI use during breastfeeding," such as studies on a larger number of women and comparing different antidepressant drugs.

The Canadian Pediatric Society, Health Canada, the American Academy of Pediatrics and the World Health Organization all recommend exclusive breastfeeding for the first six months of a baby's life.

Breast milk is considered best because the fluid meets a baby's nutritional needs, is easily digested, and contains antibodies that prevent infections and other diseases, while also promoting the mother's health.

Some of the study's authors are inventors with a provisional patent related to the research. The study was supported in part by grants from the U.S. National Institutes of Health, the U.S. Department of Agriculture and the U.S. Department of Health and Human Services.