The sleep disruption of new parenthood is both well known yet unexpected. While new parents are aware that babies need frequent nighttime care, the reality is often a nasty surprise. “What’s wrong with my baby?” new parents ask themselves, or “what’s wrong with me that I can’t get this baby to sleep?”

If you face this, you are not a bad parent, nor is your baby abnormal. You are simply asking the wrong questions. Rather than “why won’t my baby sleep?”, parents should be asking, “why do I think they should be sleeping now?” and “what am I basing my expectations on?”

There are three currently prevalent views of infant sleep norms. These are known as the cultural norm, the biomedical norm, and the biological or evolutionary norm.

The cultural norm refers to the beliefs held by different cultural groups that underpin notions of what is right.

Dominant cultural beliefs about babies in the UK are that “good babies” are not demanding and sleep through the night; a good baby is a sign of a good parent.

This cultural norm also holds that babies must be left to cry and will be spoiled if they are picked up too often.

It says babies should learn to “self-soothe” (to fall asleep by themselves) and that rocking or cuddling a baby to sleep prevents this.

These cultural beliefs about infant care are recent. They emerged in the late 1800s and early 1900s and were heavily promoted by authoritative figures such as American psychologist John B Watson and paediatrician L Emmet Holt.

They reflect the practices and lifestyles of the white middle classes 100 years ago when independence, self-reliance and stoicism were highly prized in western society.

Child-rearing experts claimed their methods would help parents raise children with these qualities.

On the other hand, biomedical (or clinical) expectations for what is normal tend to come from average values determined by classic studies, which may be presented in parenting books, websites and charts in baby clinics as guidelines for normal infant sleep.

For instance, they might suggest that at three months, babies need 14-16 hours of sleep a day, and should take three or four naps per day.

However, these recommendations often reflect only the averages from data gathered from smallish samples at specific times and places. Meta-analyses – studies which review numerous pieces of research – have found huge underlying variations in how much babies sleep.

Rather than relying on charts of average sleep patterns, we can tell a baby has slept sufficiently if they are alert and happy when they are awake.

Understanding infant sleep biology

The biological or evolutionary norm is less well known but arguably more realistic. It considers how the evolved biology of mothers and babies can help us understand infant sleep over the first months of life. Remembering that human babies are mammal babies can help us grasp this.

Mammal babies are, by definition, fed with their mother’s milk and intensively cared for after birth. Humans, like other primates, produce milk that is low in fat and high in sugar.

This means that human babies must feed often to fuel their rapidly growing brains, which at birth are only a quarter of their eventual adult size.

This explains why human infants are uniquely helpless and dependent, wake frequently at night and prefer contact with a caregiver during the first three months of life.

This biological view of infant sleep diffrs from cultural and clinical expectations of infant sleep in most western societies.

Understanding normal infant sleep biology can also help parents deal with other aspects of baby sleep. Knowing that babies are developing a circadian rhythm – adjusting their waking and sleep patterns to light and dark – will help parents understand that it’s a good thing to expose babies to daylight early in the day, and that long naps in a darkened room during daytime disrupt this developing circadian rhythm and are best avoided.

Biologically normal approaches to sleep in the first year of life can also help parents harmonise family sleep patterns.

This can be done by pushing the baby’s bedtime to later in the evening, so parents can benefit from having their own sleep aligned with their baby’s longest sleep period (usually the first sleep of the night).

Short daytime naps in daylight for babies can also reduce night waking and encourage them to obtain more of their sleep during night-time hours.

Friends and family can help parents have realistic expectations about baby sleep. Instead of asking new parents questions that frame babies’ normal behaviour as problematic (“does he sleep well?”), friends and family might instead ask something like “how are you coping with night time care?”, “are you getting enough help?” or “are you managing to go out?” Normalising questions like this emphasise that night waking is expected and that it is difficult.

They reinforce the importance of asking for and getting help from partners, family and friends, and that getting out of the house with the baby can be helpful (both for baby sleep and parental mental health).

Ultimately, empowering parents to experiment with what works for their baby and family rather than slavishly following cultural or biomedical norms reduces anxiety and improves everyone’s wellbeing. To understand what normal infant sleep involves, let your baby show you.

By Helen Ball, Professor of Anthropology and Director of the Parent-Infant Sleep Lab, Durham University Durham, Aug 6 (The Conversation)