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Co-Sleeping As Nighttime Bonding

By Pinky McKay, IBCLC

Judging by my e-mail inbox and the conversations I share with parents and health professionals, infant sleep has become a veritable industry. An industry, it seems, that is driven by fear—particularly the fear that if we dare to respond to little night howls with too many cuddles (or, heaven forbid, cuddles in parental beds), our babies may never learn to sleep alone.

When my own babies were small, neither social ideology nor wakeful babies caused me a lack of sleep; my babies slept snuggled up with me at night. My choice to co-sleep wasn’t based on research studies, it was simply “best practice” for our family… and how we all got the most sleep. Now there is a plethora of research about infant sleep, and I find it fascinating to compare this research to my own experience.

Recently, as I searched for some long-term evidence on the benefits of parent-infant co-sleeping, I came across a study by James J. McKenna and Thomas McDade called “Why Babies Should Never Sleep Alone: A review of the co-sleeping controversy in relation to SIDS, bed-sharing and breastfeeding.” The study, which involved college-age subjects, found that males who had co-slept with their parents between birth and 5 years not only had significantly higher self-esteem, they experienced less guilt and anxiety and reported greater frequency of sex. For women, co-sleeping during childhood was associated with less discomfort about physical contact and affection as adults. The co-sleepers had higher self-esteem than those who slept alone as children.

Although I am uncertain how to objectively validate my own (or my kids’!) experience in terms of this research, I concur with the wealth of evidence that supports co-sleeping as an integral part of mother-infant bonding. (In this article, co-sleeping is defined as mother and baby sleeping within sensory proximity of each other. This includes but is not limited to bed-sharing.)

Science confirms what instinct has always sung in the hearts of mothers: Nature prepares mothers and babies to be able to commence their attachment as soon as the baby is born. Immediately after a natural birth, certain hormones that are part of the birth process remain at high levels within the mother’s and baby’s bodies and play a crucial role in the formation of their relationship. If this delicate balance of hormones is allowed to function in the very first moments after birth—by keeping mother and baby warm, in skin-to-skin contact with each other, and free of distractions—they are exquisitely, chemically, primed to fall in love with each other.

Two of the major players in this hormonal cocktail are oxytocin, the hormone of affectionate bonds—also known as “the love hormone”—and prolactin, a hormone critical for the initiation of lactation, which is often referred to as “the mothering hormone.” Oxytocin is involved in whatever facet of love we consider—it is released during lovemaking and also has been shown to evoke maternal behavior if injected into the brains of virgin rats. Oxytocin itself is part of a complex hormonal balance. A sudden release of oxytocin creates an urge toward loving, which can be directed in different ways, depending on the presence of other hormones. This is why there are different types of love. When oxytocin is found with a high level of prolactin, for example, the urge to love is directed toward babies.

Fortunately, whatever the birthing experience, it seems nature allows more than a single chance to cement the foundation for a loving relationship and to reinforce the bonding process. Learning to love is an ongoing process for mother and baby, and hormones continue to play an important role, day and night.

As a woman breastfeeds, for instance, she receives doses of oxytocin (which stimulates the milk ejection reflex) and prolactin (which has a calming effect on her as she breastfeeds). Endorphins, the hormones of pleasure and transcendence, are also released during breastfeeding and encourage the mother to continue. In turn, endorphins are transferred through the mother’s milk to her baby, giving the child a sense of contentment as he or she breastfeeds. Since prolactin levels are highest during night feeds, it makes sense to consider that proximity to her infant at night would elevate the love a mother feels for her infant. Perhaps, without pressure to teach their babies to sleep all night as soon as possible, mothers could appreciate night-time breastfeedings as an extra opportunity to bond with their babies.

For any mother snuggling a baby against her body, nuzzling her face into her infant’s baby-fine hair and smelling that sweet newborn breath, research verifying that mothers and babies feel best when they are close to each other would hardly seem necessary. However, there is indeed scientific evidence that mothers and babies are hardwired to the experience of togetherness.

One argument in favor of continuous mother-baby togetherness maintains that infants get to know and bond with their mother through all of their senses—eye contact, the sounds of the mother’s voice, her touch and smell.