The term, preterm and growth-restricted baby

The term, preterm and growth-restricted baby

Image described by caption and surrounding text.

Assessment of gestational age

Most babies are born at term and are healthy (Figure 40.1). However, low birthweight (LBW) babies, that is <2.5 kg at birth, comprised 7% of livebirths in 2014 (ONS 2015). Babies weighing <1.5 kg at birth are classed as very low birthweight and babies <1 kg as extremely low birthweight.

Babies may be LBW because they are born preterm, because they are constitutionally small or because intrauterine growth has not followed the expected trajectory (growth restriction). The baby may at increased risk of perinatal morbidity or mortality. Accurate assessment of gestational age is essential to ensure appropriate care. A useful assessment tool is the Ballard Score (Lissauer et al. 2016).

Preterm babies

A preterm baby is one born alive before 37 weeks’ gestation (Figure 40.2). Worldwide, prematurity is the leading cause of death before the age of 5 years. Subclassifications include very preterm (i.e. 28–32 weeks’ gestation) and extremely preterm: (<28 weeks’ gestation). A baby may be delivered preterm deliberately (elective preterm birth) if it is medically indicated. Examples of such situations are higher-order multiple pregnancies, or maternal or fetal disease where continuation of the pregnancy would be risky for the health of mother or fetus. However, the majority of preterm labours are idiopathic (spontaneous.)

Risk factors for spontaneous preterm birth include:

  • Maternal infection
  • Uterine malformations
  • Multiple pregnancy
  • Maternal substance misuse
  • Domestic abuse.

Characteristics of the preterm baby

The appearance and characteristics are dependent on the gestation at birth. The skin is thin and at very early gestations the dermis is almost gelatinous, eyelids fused and fat stores absent. Nails are small and soft and lanugo may be seen on the skin. Body systems such as the respiratory and gastrointestinal systems are immature and do not function well. The muscle tone is poor and the infant lies with limbs extended. Table 40.1 shows maturational stages at different gestations.

Problems of the preterm baby are:

  • Birth asphyxia and birth trauma
  • Respiratory problems/chronic lung disease
  • Feeding/nutritional difficulties
  • Poor thermoregulation
  • Susceptibility to infection
  • Intraventricular haemorrhage
  • Jaundice.

Small for gestational age babies

The definition of small for gestational age (SGA) is an estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th centile; severe SGA is an EFW or AC below the 3rd centile. The fetus may be constitutionally (‘normally’) small, with growth appropriate for maternal ethnicity or size (RCOG 2013) or the cause may be pathological. SGA is not synonymous with intrauterine growth restriction (IUGR). Growth restriction implies the presence of pathology that is interfering with the fetal growth potential (Figure 40.3). Pathologies may be non-placenta mediated such as fetal anomalies or infection, or placenta-mediated such as maternal disease that may affect transplacental transfer of nutrients.

Risk factors for IUGR include:

  • Previous SGA baby, stillbirth or pre-eclampsia
  • Maternal substance misuse
  • TORCH infections (toxoplasmosis, other – syphilis, parvovirus, varicella-zoster, rubella, cytomegalovirus, herpes)
  • Maternal disease such as pre-existing diabetes, renal disease or chronic hypertension
  • Repeated antepartum haemorrhage
  • Chromosomal anomalies.

Characteristics of the IUGR baby

Constitutionally small babies will show gestationally appropriate development and appearance. Growth-restricted babies usually have a head circumference appropriate for gestational age. However, fat stores are poor or absent and there is poor skeletal muscle mass. The skin is often dry, meconium stained and appears loose, with skin folds. Nails may be long and hair abundant. The abdomen may be scaphoid, AC reduced, and ribs visible. The umbilical cord may be thin and meconium stained. The baby often has a wizened, malnourished appearance.

Problems of a growth-restricted fetus are:

  • Birth asphyxia
  • Meconium aspiration
  • Hypoglycaemia
  • Polycythaemia
  • Jaundice
  • Poor thermoregulation
  • Pulmonary haemorrhages
  • Necrotising enterocolitis.

Jun 19, 2019 | Posted by in MIDWIFERY | Comments Off on The term, preterm and growth-restricted baby

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