[6] From 1975 to 1997, Welch operated a private practice, specializing in the treatment of emotional, behavioral and developmental disorders, including autism, maintaining offices in New York City and Greenwich, CT.

In 2010 Welch was jointly appointed in Columbia University's Department of Pediatrics, where she is conducting research on Family Nurture Intervention in the neonatal intensive care unit of New York-Presbyterian Hospital.

[8][12][13] At Columbia University Medical Center, she began preclinical research investigating secretin and oxytocin in the brain and the effects of combined oxytocin/secretin on an animal model of inflammatory bowel disease.

Welch and Gershon later established the Columbia University Brain Gut Initiative to further their understanding the mechanisms of nurture and they condition the brain-gut axis.

[15] Welch lives in New York City with her partner, Robert J. Ludwig, the managing director of the Nurture Science Program at Columbia University Medical Center's Department of Pediatrics.