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Prem vs term?

A baby born at term and a baby born pre-term, will look and behave very differently. In this article, Dr Kain introduces some of the key differences.
A funny image of a toddler wearing adult-style glasses rests against a background covered with question marks.
© Shutterstock

A baby born at term and a baby born preterm, will look and behave very differently. Let’s learn how.

A few definitions before we get started.

  • The gestational age refers to the ‘age’ of the neonate during the pregnancy. It is measured in weeks.
  • A term pregnancy refers to babies born after 37 weeks gestation.
  • Babies born before 37 weeks are considered pre-term, more commonly known as premature.
  • Babies born past 42 weeks are considered to be post-term.

That being said, there are stages of prematurity and post maturity. Let’s consider the World Health Organisation’s (2016) neonatal classifications in the table below, based on maturity at birth.

Definition of maturity at birth Completed weeks of gestation
Extremely preterm < 28
Very preterm 28 – <32
Moderate to late preterm 32 – <37
Term 37 – 41
Post-term ≥42 weeks

Consider the pictures below of the premature baby on the left, and the term baby on the right. What differences do you notice?

A premature baby is pictured on the left and a full term baby is pictured on the right©Shutterstock

The most obvious difference is their size. Term babies have noticeably more body fat. For example, you may notice breast tissue, chubby arms, legs and tummies. Premature babies appear ‘skinny’ in comparison. Their lack of body fat – a type of fat known as brown fat that protects newborns from hypothermia, means they are at risk of becoming very cold, very quickly. This is one reason why it is so important to keep all babies, but especially premature babies warm.


The tone of the baby is another important difference. Term babies tend to adopt a frog-like, fully flexed posture. This posture also helps them to keep warm. Premature babies however, have a lack of body tone and are quite ‘floppy’ in comparison. This increases their risk of becoming cold after birth.

Skin colour

The skin colour difference between premature and term babies is also significant. Premature babies tend to look quite red. The more premature the baby, the more translucent and gelatinous their skin will look and feel. Premature skin is very fragile because the stratum corneum (the outermost layer of the skin) is underdeveloped (Oranges, Dini, & Romanelli, 2015).

Body hair

Did you know premature babies also tend to be quite hairy? This premature hair growth, lanugo,is the first hair produced by fetal hair follicles. Lanugo is present from around 20 weeks gestation. It is very fine, soft and usually not pigmented (Moore, Persaud, & Torchia, 2013). It can be found everywhere on a baby’s body, except on the palms, lips, and soles of the feet. Most fetuses develop lanugo around the fourth or fifth month of pregnancy and it disappears as the premature baby reaches term.

Other differences

In terms of behaviour, the body systems of the premature infant are also immature. This means that the baby is prone to

  • apnoea – periods of 15 seconds or more, where they don’t breathe
  • jaundice – due to immaturity of the liver
  • feeding problems – because the suck/swallow reflex is not developed until 33 weeks gestation and
  • delays in the transition of fetal to adult circulation (more on this later).

Your task

Have you had contact with pre-term babies or have a story to share? Please post your thoughts and experiences in the comments link below.


Moore, K. L., Persaud, T. V. N., & Torchia, M. G. (2013). The developing human: clinically oriented embryology (9th ed.). Philadelphia, PA: Saunders/Elsevier.

Oranges, T., Dini, V., & Romanelli, M. (2015). Skin Physiology of the Neonate and Infant: Clinical Implications. Advances in Wound Care, 4(10), 587-595.

World Health Organisation (2016). Preterm Birth Fact Sheet.

© Griffith University
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