Why is my Baby Irritable? – Six Points to Understanding Infant Sleep

A common problem in primary care is to be asked for guidance on the care of an irritable baby. In this article I describe non-medical problems which, in my experience, actually dominate over medical problems.

As a GP I have focused on the care of mothers and babies for about 40 years and have seen well over 10,000 families. For the rest of this article, let’s assume that the irritable baby in question is less than 12 weeks old.

To oversimplify the situation, my experience is that in this age group two problems dominate – fatigue and hunger.

So, if you are faced with an overtired mother and an irritable baby who seems to cry excessively, a very simple algorithm is as follows. Exclude poor weight gain and take a simple sleep history.

In this article I am going to focus on fatigue, but in terms of ensuring adequate nutrition it is easy to measure weight, to calculate weight gain per day and percentiles.  For children under 12 weeks, I recommend measuring and graphing these three variables at every visit.

Weight or Hunger

Unfortunately, hunger is very common in our culture.  If weight gain per day is less than 30 gm per day, if percentiles are dropping, if the baby is irritable at the end of the feed, if feeding times are prolonged i.e., more than a total of 20-30 minutes then a feeding review is needed.  Do whatever is needed to ensure that the baby finishes all their feeds fully satisfied.  I can address hunger and feeding in more detail in a later article. Today, we are focused on sleep.

Sleep, Fatigue or Over-tiredness

Total sleep volume that is needed to be well in the first few months is almost always more than 16 hours per day. This varies with weight but only a little.  Heavier babies can cope with a little less sleep and light babies need more.  To put that point in its reverse, lighter babies become over-tired more rapidly and need shorter waking times.

I teach six main points which give a useful and practical understanding of infant sleep.

  1. Sleep is Cyclical
  • During a block of sleep it is normal and healthy to awaken and resettle multiple times.
  • For a newborn baby, these cycles are about 45 minutes long. The waking events will last generally 30-90 seconds. The majority should be silent, and you will be unaware that they occur.
  • In overtired babies they may waken at the 45-minute point and have trouble getting back to sleep. Thus, if your baby is calling for assistance every 45 minutes it may be a sign of fatigue.
  • In very overtired babies, sleep cycles can ‘break down’ to 20-minute cat naps.
  • In a block of sleep, a baby awakens and returns to sleep multiple times. What forces drive a return to sleep? To simplify very complex events, I identify two things:  Tiredness and ‘cues of sleep’.
  1. Cues of Sleep
  • It is useful to think of the sleep achievement event as being driven by a combination of tiredness and external cues of sleep i.e., the things which are going on around the baby at the time.
  • Again, to simplify these cues can be divided into parent dependent and parent independent.
  • When a baby or child is put to bed at the beginning of a block of sleep tiredness dominates. Cues of sleep achievement are outweighed by tiredness and they are more likely to achieve sleep efficiently.
  • As a block of sleep progresses tiredness reduces and cues of sleep become more important in achieving a return to sleep.
  • If a baby is put to sleep using parent dependent cues i.e., holding, rocking, patting, feeding then there is an increased chance that the baby will request those cues be repeated later in that block of sleep.
  • Cues of sleep which are parent independent are more useful. I use a term ‘parent-lite settling’.  So, we prepare a baby for sleep, but the final transition is achieved by the baby alone as often as is possible.
  1. Cues of Sleep are Learned
  • To make this point I use adult experience. Learning to sleep with a partner. Moving to a new suburb or street with different noises outside the home. Buying a new bed.  We have all had these experiences.
  • So, cues of sleep can be changed and relearned.
  • Babies actually do this very efficiently.
  1. Sleep Achievement and Sleep Maintenance are Usefully Regarded as Learned Skills
  • By combining two points i.e., sleep is in part cue dependent and cues are learned I develop a very important point.
  • Going to sleep and maintaining sleep are usefully considered learned skills.
  1. Fatigue Interferes With the Learned Skill of Sleep Achievement
  • This point may seem counter-intuitive but almost every single mother that you care for will agree that she has had a personal experience of becoming so tired that while she is desperate to get sleep her mind will not turn off. This is critically important for children.
  • Therefore, it is important to ensure the child does not become over tired.
  • A newborn can become overtired in 10 – 15 minutes.
  • Low weight babies are more prone to fatigue and heavier babies a little more resistant.
  • For the age group under discussion waking times need to be fairly short i.e., 20-30 minutes over-night and something like 45 minutes during day light. This time includes feeding, changing, cuddles and any social time.
  • To put it another way in the first month of life my ambitions for a baby are simply feed, sleep, and grow.
  1. Cues of Sleep Achievement That are Parent Independent are the Most Useful for Family Life
  • A baby who achieves sleep with parental care is preordained to request that care again at some point in the block of sleep. Minimise sleep transitions which involve parental assistance and allow a child to achieve sleep alone.
  • Adopt a ‘parent-lite’ approach to sleep achievement. Be there and be supportive but keep it minimal rather than the reverse. The baby needs to feel parental love and support but when it is time to be asleep leave them alone to finalise the last steps in sleep achievement.
  • A parent has a major and positive role to play when the baby is awake and maybe even when sleepy but once the baby is ready to be finally asleep these events are best managed by the baby alone. This is true from the time of birth.

Conclusion to Assessing an Irritable Baby of Less Than 12 Weeks

  • Take steps to check that a baby is being well fed by whatever technique ensures adequate growth.
  • Avoid over-tiredness and the following points assist understanding.
    • Sleep is cyclical with blocks of sleep which include multiple short episodes of arousal followed by a return to sleep
    • Sleep achievement is in part cue dependent
    • Cues of sleep are learned can be altered and relearned
    • Sleep achievement and sleep maintenance are usefully regarded as learned skills
    • Avoid children becoming over tired as this interferes with the learned skill of sleep achievement
    • Minimise cues of sleep achievement that are parent dependent. Take a ‘parent lite’ approach.
  • It is my experience that ensuring complete feeding and avoiding over-tiredness linked to the learning of parent-lite cues of sleep will resolve that large majority of events where the presentation is an irritable infant aged 12 weeks or below.
Dr Brian Symon
This article was contributed by Dr Brian Symon. He has more than 30 years’ experience working with parents and babies experiencing problems of sleep, feeding, growth and behaviour. You can find out more about Dr Symon’s work at his website – The Babysleep Doctor.
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