A deep and enduring emotional bond between an infant and caregiver, which provides a sense of security to the child.

A pattern of infant behaviour or development that reflects evolutionary adaptations in human biology, rather than culturally constructed expectations.

Bed-sharing refers to a sleep arrangement in which an infant and an adult (usually a parent or caregiver) sleep together on the same bed. Bed-sharing can be the result of intentional choices or as an accident.

The act of feeding an infant with milk directly from the breast. It provides nutrition, immune protection, and facilitates bonding and co-regulation.

The body’s internal biological clock that regulates the sleep-wake cycle and other physiological processes over a 24-hour period.

The dynamic process by which caregivers and infants mutually influence and adjust each other’s emotional and physiological states, particularly in the context of sleep and soothing.

You will see this term used most frequently on BASIS twin sleep page as co-bedding refers to specifically when multiple babies are put to sleep on the same bed, cot, or sleep surface.

An umbrella term referring to situations where an infant sleeps in close proximity to a caregiver, including bedsharing (same surface) and room-sharing (same room, different surfaces).

A situation where evolved infant behaviours (e.g., frequent night waking) conflict with modern cultural expectations or environments (e.g., sleeping through the night).

Harm elimination aims to completely prevent or eliminate the possibility of a harmful behaviour or outcome by discouraging or prohibiting the behaviour altogether. In the infant sleep research world, an example of harm elimination could be advising that parents never share a bed with their baby, regardless of context.

Harm reduction (or harm minimisation) accepts that some risky behaviours will occur and focuses on reducing the negative consequences associated with them, rather than trying to eliminate the behaviour entirely. For infant sleep safety, in practice harm reduction could look like providing information, tools, and support to help people make safer choices such bed-sharing without known hazards.

A term used to describe the complex interplay of biological, cultural, environmental, and social factors that shape infant sleep behaviour.

The alignment of sleep and waking patterns between a caregiver and infant, which can promote better rest and bonding for both parties.

A form of clinical depression affecting parents after childbirth, often linked to factors such as disrupted sleep, hormonal changes, and social support.

A caregiving approach that involves noticing and sensitively responding to an infant’s cues, including sleep-related needs.

When an infant sleeps in the same room as a caregiver but on a separate surface, such as a cot or bassinet. Recommended for the first 6–12 months to reduce SIDS risk.

Also referred to as behavioural sleep management by academics and other professionals, sleep training is set of methods aimed at modifying an infant’s sleep behaviour, often to promote longer night-time sleep. These vary widely in approach and evidence base.

The rhythm or schedule of an infant’s periods of sleeping and waking across a 24-hour period, which changes significantly with age and development and from baby to baby.

SIDS refers to the sudden and unexplained death of an apparently healthy baby, usually during sleep, that remains unexplained even after a thorough investigation.

SUDI is a broader category that includes all sudden and unexpected deaths of infants under 12 months, regardless of cause. It includes:

Unexplained deaths (like SIDS)

Explained deaths (e.g., accidental suffocation, infections, congenital anomalies)

The ambient temperature and bedding conditions in which an infant sleeps, which can influence comfort, arousal, and risk of overheating or SIDS.

A sleep situation where an infant is left alone, typically in a separate room, which contrasts with practices like co-sleeping or room-sharing