From 1982 to 1984 Karp practiced pediatrics with pediatrician Paul Fleiss in Los Angeles, California. He then opened his own practice in Santa Monica, where he continued to see patients until 2005. He was assistant clinical professor of pediatrics at the UCLA School of Medicine from 1989 to 2009, where he served as pediatric liaison to the Child Abuse Team. He appeared as a regular contributor to the Lifetime cable television show Growing Up Together from 1990 to 1992. In 2009, he became an assistant professor of pediatrics at the USC Keck School of Medicine. Karp is a founding board member of Healthy Child Healthy World, and has served on the advisory boards of the Green Guide, Babycenter.com, Parents, Ser Padres, and American Baby magazines.
Infant calming and sleep technique
Karp's infant calming technique is supposed to be based on recreating the essential elements of the experience of living in the womb. Human babies, according to Karp, are born less developed than other mammals. Karp calls the first three months of life the "fourth trimester." Karp hypothesizes that all babies are born with a "calming reflex" that quickly relaxes most fussy babies when they are stimulated in a way that resemble sensations that babies experience in the womb. Karp calls the ingredients of his method for soothing young babies the "5 S's": tight swaddling, side/stomach position, shushing, swinging and sucking. Regarding sleep, Karp recommends nightly swaddling and sound and motion sleep cues to help babies establish a circadian rhythm and to promote infant sleep.
Criticism
CBS news reports that "Critics say Karp is riding to fame on the strength of his patients' VIP parents, who include Michelle Pfeiffer, Pierce Brosnan and Madonna. Endorsements from several stars appear on his book jacket and video cover." Some doctors have also expressed concern that babies may accidentally be left to sleep face down, a position which increases the risk of sudden infant death syndrome. Karp explicitly warns parents not to leave babies in this position. Ralph Frenken has argued against Karp's recommendation of the use of tight swaddling and the concept of a "calming reflex." The criticism is that the effect of swaddling is not based on reflexes because a releasing stimulus is missing, because swaddling most probably works by the decrease of proprioceptive and tactile stimulation and the reflex response is missing, because any reflex always consists of a movement released by muscles. The child does not move but falls asleep by swaddling. Additionally, no known reflex alters the state of consciousness, but swaddling obviously does. Lactation and breastfeeding expert, Nancy Mohrbacher, collected several scientific studies which demonstrated negative aspects of swaddling on newborn infants. In 2010, researchers studied the effects of video instruction concerning swaddling, side positioning, white noise, jiggling, and sucking on parents' ability to calm fussing babies. The results against a control group were statistically insignificant compared to traditional methods.
