Week 1 of a Baby’s Life: Reflexes and Adaptation

HIGHLIGHTS

• The first week is a key stage of adaptation to the outside world
• Most skin changes are part of normal physiology
• Primitive reflexes help the baby survive
• Frequent feeding and close contact with the mother support successful breastfeeding
• Sleep may reach up to 19 hours per day

IN THIS ARTICLE

• General newborn adaptation
• Physiology of the first week
• Newborn thermoregulation
• Primitive (innate) reflexes
• What a baby can do
• Feeding and spit-ups
• Sleep
• Taste and smell
• The newborn adjustment period

GENERAL NEWBORN ADAPTATION

The first week of life is a period of intense adaptation to life outside the mother’s body.

The baby’s organism is rapidly reorganizing, innate survival mechanisms are activated, and the mother becomes the main source of safety, warmth, and comfort.

A baby is considered a newborn during the first 28 days of life; however, the very first week is the most intensive in terms of physiological and behavioral changes. After nine months of a protected intrauterine environment, the baby adapts to open space, a new rhythm of life, and a much larger world. Through her voice, scent, touch, and care, the mother helps the baby adapt gently and safely.

PHYSIOLOGY OF THE FIRST WEEK

In the first days of life, a newborn’s skin may change noticeably, which often causes concern for parents.

Physiological Jaundice

On days 2–4 of life, a baby may develop physiological jaundice — a temporary increase in indirect bilirubin levels in the blood.

This is a transient condition that:

• does not require treatment
• resolves on its own
• occurs in about 50% of full-term and up to 80% of preterm infants

Other Skin Changes

During this period, the following may also appear:

• toxic erythema of the newborn
• infant acne

These conditions are not related to the mother’s diet and do not require strict dietary restrictions or medication.

NEWBORN THERMOREGULATION

A newborn’s thermoregulation system is still immature:

• the baby can easily overheat
• and can just as easily become chilled

Newborns do not sweat yet; therefore:

• children under one year should not be taken to saunas or steam baths
• clothing and outdoor conditions should be chosen carefully

PRIMITIVE REFLEXES

Primitive reflexes are innate responses essential for survival during the first weeks of life. At this stage, most movements and reactions are reflex-based, as voluntary skills have not yet developed.

As the nervous system matures, these reflexes gradually fade and transform into purposeful movements. Their presence, symmetry, and gradual weakening are important indicators of normal neurological development.

The main reflexes of the first week include:

• sucking and rooting reflexes
• protective reflex
• grasp reflex
• proboscis reflex
• support and automatic stepping reflex
• Moro (startle) reflex
• Babinski reflex
• asymmetrical tonic neck reflex
• Galant and Perez reflexes

WHAT A BABY CAN DO

During the first week, a baby:

• moves arms and legs chaotically
• adapts to open space
• begins to recognize and respond to the mother’s voice

There are no conscious skills yet — all movements are primarily reflex-based.

FEEDING AND SPIT-UPS

In the first days of life, a baby may lose up to 10% of birth weight — this is a normal physiological process.

Breastfeeding

• breast milk is the optimal source of nutrition
• feeding on demand is recommended
• feeding frequency may reach every hour

Spit-Ups

Spit-ups are common in the first months of life.

• a normal volume in the first week is about one tablespoon
• if the volume approaches that of a full feeding, medical attention is required

SLEEP

During the first week of life, a newborn:

• may sleep up to 18–19 hours per day
• is awake only about 15–20% of the time

Short periods of wakefulness are best used for:

• cuddling
• gentle interaction
• skin-to-skin contact

TASTE AND SMELL

Newborns:

• have more taste receptors than adults
• can already distinguish sweet and bitter tastes
• begin to recognize salty taste closer to 5 months of age

Taste preferences start forming before birth and are influenced by the mother’s diet.

From birth, babies actively respond to smells:

• turning away from unpleasant odors
• turning toward the smell of their mother’s milk

THE NEWBORN ADJUSTMENT PERIOD

The mother is the baby’s main reference point in the new world.

Her voice, scent, and warmth help the baby feel safe.

Frequent skin-to-skin contact:

• reduces stress levels in the baby
• supports the establishment of breastfeeding
• strengthens the emotional bond between mother and child