This website is intended for healthcare professionals.
LOGIN
JOIN US
Subscriber log in
Trial log in
  

Prematurity/Preterm birth

Prematurity is defined as birth occurring before the end of the 37th gestational week, regardless of birth weight. Most preterm babies are appropriately grown; some are small for gestational age (SGA), while a small number are large for gestational age (LGA), mostly where the mother has diabetes.

Causes of preterm labour

 

Spontaneous causes

  • 40% unknown
  • Multiple gestation
  • Hyperpyrexia as a result of viral or bacterial infection
  • Premature rupture of the membranes caused by maternal infection
  • Maternal short stature
  • Maternal age and parity.
  • Poor obstetric history; history of preterm labour
  • Cervical incompetence
  • Poor social circumstances

Elective causes

  • Pregnancy-induced hypertension, pre-eclampsia, chronic hypertension
  • Maternal disease: renal, cardiac
  • Placenta praevia, abruptio placenta
  • Rhesus incompatibility
  • Congenital abnormality
  • IUGR

     

Appearance of the preterm baby

  • Posture appears flattened with hips abducted, knees and ankles flexed
  • Babies are generally hypotonic with a weak and feeble cry
  • Head is in proportion to the body
  • The skull bones are soft with large fontanelles and wide sutures
  • Chest is small and narrow and appears underdeveloped due to minimal lung expansion during fetal life
  • Abdomen is prominent because the liver and spleen are large and abdominal muscle tones poor
  • Umbilicus appears low in the abdomen because linear growth is cephalocaudal (more apparent nearer to the head than the feet)
  • Subcutaneous fat is laid down from 28 weeks' gestation; therefore its presence and abundance will affect the redness and transparency of the skin
  • Vernix caseosa is abundant in the last trimester and tends to accumulate at sites of dense lanugo growth, i.e. face, ears, shoulders, sacral region
  • Ear pinna is flat with little curve, the eyes bulge, the orbital ridges are prominent
  • Nipple areola is poorly developed and barely visible
  • Cord is white, fleshy and glistening
  • Plantar creases are absent before 36 weeks
  • In girls, the labia majora fail to cover the labia minora; in boys, the testes descend into the scrotal sac in about the 37th gestational week

Management at birth

Current cot availability in the NICU, transitional care unit (as applicable) and postnatal ward should be known. The ambient temperature of the birthing room should ideally be between 23°C and 25°C. The neonatal resuscitaire should be checked and ready for use. A second person skilled in resuscitation skills should be present. On cutting the cord, leave an extra length, in case access to the umbilical vessels is necessary later. The Apgar score is traditionally scored at 1 and 5 minutes. Labelling of the preterm/LBW baby is particularly important because separation of mother and baby could happen at any time if the baby's condition becomes unstable. A detailed but expedient examination of the baby should be carried out. Once it is established that the baby is healthy, the midwife may attempt to normalise care by emphasising to the parents the importance of preventing cold stress and promoting skin-to-skin contact for a period of up to 50 minutes. Ensure that the baby is thoroughly dried before skin-to-skin contact is attempted. The baby's body temperature should be maintained between 36.5°C and 37.3°C.

Thermoregulation Thermoregulation is the balance between heat production and heat loss. The prevention of cold stress, which may lead to hypothermia (body temperature < 36°C), is critical. Newborn babies are unable to shiver, move very much or ask for an extra blanket, and therefore rely upon physical adaptations that generate heat by raising their basal metabolic rate and utilising brown fat deposits. As body temperature falls, tissue oxygen consumption rises as the baby attempts to raise its metabolic rate by burning glucose to generate energy and heat. Care measures should aim to provide an environment that supports thermoneutrality.

  • All preterm babies are prone to heat loss because their ability to produce heat is compromised by their immaturity, so factors like their large surface area to weight ratio, their varying amounts of subcutaneous fat and their ability to mobilise brown fat stores will be affected by their gestational age.
  • During cooling, the immature heat-regulating centres in the hypothalamus and medulla oblongata fail, to different degrees, to recognise and marshal adequately coordinated homeostatic controls.
  • Preterm babies are often unable to increase their oxygen consumption effectively through normal respiratory function, and their calorific intake is often inadequate to meet increasing metabolic requirements.
  • Their open resting postures increase their surface area and insensible water losses.
  • Babies under 2.0 kg may need incubator care when the baby is not in skin-to-skin contact with either parent. The warm conditions in an incubator can be achieved either by heating the air to 30-32°C (air mode) or by servo-controlling the baby's body temperature at a desired set point (36°C). In servo mode, a thermocouple is taped to the upper abdomen and the incubator heater maintains the skin at that site to a preset constant. Babies are clothed with bedding, in a room temperature of 26°C.
  • Most preterm babies between 2.0 and 2.5 kg will be cared for in a cot, in a room temperature of 24°C.

Hypoglycaemia Low blood glucose concentration is more likely to occur in conditions where babies become cold or where the initiation of early feeding (within the first hour) is delayed.

  • The aim is to maintain the true blood sugar above 2.6 mmol/dl.
  • The preterm baby may be sleepier, and attempts to take the first feed may reflect gestational age.
  • Total feed requirements (60 ml/kg on the first day, with 30 ml/kg increments per day thereafter) may not be taken directly from the breast and supplementary feeds can be given by cup.

Both preterm and SGA babies benefit from human milk because it contains long-chain polyunsaturated omega 3 fatty acids, which are thought to be essential for the myelination of neural membranes and retinal development. Preterm breast milk has:

  • A higher concentration of lipids, protein, sodium, calcium and immunoglobulins
  • Low osmolarity
  • Lipases and enzymes that improve digestion and absorption.

The baby is normally able to co-ordinate breathing with sucking and swallowing reflexes between 32 and 36 weeks. Preterm babies are limited in their ability to suck by their weak musculature and flexor control, which is important for firm lip and jaw closure. Before 32 weeks, most healthy preterm babies will need to be tube-fed on a regular basis, usually on a 3-hourly regime with breast milk or formula milk.

The care environment

The ideal environment should provide a cycle of day and night, regular nourishment, rest, stimulation and loving attention. The mother's desire to be involved is seen as an essential element in the success of caring for LBW babies on postnatal wards. Handling and touchKangaroo care (KC) is used to promote closeness between a baby and mother and involves placing the nappy-clad baby upright between the maternal breasts for skin-to-skin contact, for varying periods of time that suit the mother.

Noise and light hazards

  • Noise should be kept to a minimum.
  • In dimmed lighting conditions, preterm babies are more able to improve their quality of sleep and alert status.
  • Reduced light levels at night will help to promote the development of circadian rhythms and diurnal cycles.
  • Screens to shield adjacent babies from phototherapy lights are essential.

Sleeping positionPreterm babies have reduced muscle power and bulk, with flaccid muscle tone; therefore their movements are erratic, weak or flailing. Without support they may, to differing degrees, develop head, shoulder and hip flattening, which in turn can lead to poor mobility. Nesting the more immature preterm babies into soft bedding, in addition to the use of close flexible boundaries, helps to keep their limbs in midline flexion. However, it is vital that they are nursed in a supine position to prevent asphyxia.

Sudden infant death syndrome (SIDS)

There is a need to remind parents constantly of the risk factors and safety procedures (feet-to-foot sleeping position, smoke-free room) associated with SIDS, alongside teaching them to keep their babies warm. The midwife needs to explain that families should take into consideration time of year, gestational age and postnatal age. Parental training on 'what to do if my baby stops breathing' should be offered to parents but the decision to receive training should be their choice.

The prevention of infection

LBW babies, particularly preterm ones, are especially vulnerable to infections caused by immaturity of their host defence systems.

The Practising Midwife featured article

Sweet memories of a bitter experience: a parent's view 2015; 18(10): 30 - 32 Inistar Ulhaq

Further reading

World Health Organization (2015) Preterm birth. http://www.who.int/mediacentre/factsheets/fs363/en/

NHS Choices (2015). Pregnancy and baby: Premature labour and birth. http://www.nhs.uk/conditions/pregnancy-and-baby/pages/premature-early-labour.aspx

Institute of Medicine (US) (2007). Preterm birth: Causes, consequences, and prevention. http://www.ncbi.nlm.nih.gov/pubmed/20669423

 

Return to index