|For as far back as you care to go, mothers have followed
the protective and convenient practice of sleeping. with their infants. Even now, for
the vast majority of people across the globe, "co-sleeping" and nighttime
breast-feeding remain inseparable practices. Only in the past 200 years, and mostly in
Western industrialized societies, have parents considered it normal and biologically
appropriate for a mother and infant to sleep apart.
In the sleep laboratory at the University of California's Irvine School of
Medicine, my colleagues and I observed mother-infant pairs as they slept both apart
and together over three consecutive nights. Using a polygraph, we recorded the
mother's and infant's heart rates, brain waves (EEGs), breathing, body temperature,
and episodes of nursing. Infrared video photography simultaneously monitored their
We found that bed-sharing infants face their mothers for most of the night, and
that mother and infant are highly responsive to each other's movements, wake more
frequently, and spend more time in lighter stages of sleep than they do while sleeping
alone. Bed-sharing infants nurse almost twice as often, and three times as long per
bout, as they do when sleeping alone. But they rarely cry. Mothers who routinely sleep
with their infants get at least as much sleep as mothers who sleep without them.
In addition to providing more nighttime nourishment and greater protection,
sleeping with the mother supplies the infant with a steady stream of sensations of the
mother's presence, including touch, smell, movement, and warmth. These stimuli can
perhaps even compensate for the human infant's extreme neurological immaturity at
Co-sleeping might also turn out to give some babies protection from sudden infant
death syndrome (SIDS), a heartbreaking and enigmatic killer. Co-sleeping infants nurse
more often, sleep more lightly, and have practice responding to maternal arousals.
Arousal deficiencies are suspected in some SIDS deaths, and long periods in deep sleep
may exacerbate this problem. Perhaps the physiological changes induced by co-sleeping,
especially when combined with nighttime breastfeeding, can benefit some infants by
helping them sleep more lightly. At the same time, co-sleeping makes it easier for a
mother to detect and respond to an infant in crisis. Rethinking another sleeping
practice has already shown a dramatic effect: in the United States, SIDS rates fell at
least 30% after 1992, when the American Academy of Pediatrics recommended placing
sleeping babies on their backs, rather than face down.
The effect of co-sleeping on SIDS remains to be proved, so it would be premature to
recommend it as the best arrangement for all families. The possible hazards of
co-sleeping must also be assessed. Is the environment otherwise safe, with appropriate
bedding materials? Do the parents smoke? Do they use drugs or alcohol? (These appear
to be the main factors in those rare cases in which a mother inadvertently smothers
her child.) Since co-sleeping was the ancestral condition, the future for our infants
may well entail a borrowing back from ancient ways.