The Normal Newborn
The vast majority of babies are born at term, in good condition and do not require any medical involvement. Most babies in the UK are born in hospital, where a paediatrician is usually available to attend ‘high risk’ deliveries where it may be anticipated that resuscitation will be required. A healthy newborn term infant cries soon after birth, and is pink with good muscle tone, a normal heart rate and regular respiration. Once the cord has been clamped and cut, the baby can be dried and given straight to the mother for skin-to-skin contact and to establish breast-feeding. Newborn babies, especially if they are premature, are covered in a waxy material called vernix. Post-term infants may have very dry, cracked skin. Babies pass a green–black stool called meconium which changes to a normal yellow–brown stool after a few days. It is recommended that infants are given vitamin K at birth to prevent potentially catastrophic bleeding. Newborn infants are routinely examined within the first few days to exclude congenital abnormalities (see Chapter 7) and have blood taken from a heel-prick around day 5 to screen for hypothyroidism and metabolic disorders (see Chapter 8).
Asphyxia and Resuscitation
The perinatal mortality rate (currently 7 per 1000) has halved in the UK over the last 20 years, largely due to improvements in obstetric care. The reduction in neonatal mortality rate (now less than 3 per 1000 live births) is due to improvements in the management of babies with complex congenital abnormalities and to improved care of preterm infants. Some babies still require immediate resuscitation after birth, and personnel attending deliveries must be trained in effective and rapid resuscitation. The need for resuscitation can often be anticipated and a paediatrician should be in attendance. Such situations include:
- Fetal distress
- Thick meconium staining of the liquor
- Emergency caesarean section
- Instrumental delivery
- Known congenital abnormality
- Multiple births.
The condition of the infant after birth is described by the Apgar score (see opposite). Each of five parameters is scored from 0 to 2. A total Apgar score of 7–10 at 1 min of age is normal. A score of 4–6 is a moderately ill baby and 0–3 represents a severely compromised infant who may die without urgent resuscitation. Such babies will often require intubation and may require cardiac massage. In the most depressed babies IV drugs such as adrenaline (epinephrine) and bicarbonate may be necessary to re-establish cardiac output. The outcome for these infants may be poor.
Some infants in poor condition at birth may have suffered a hypoxic or ischaemic insult during pregnancy or labour. A healthy fetus can withstand brief physiological hypoxia, but an already compromised fetus may become exhausted and decompensate with build-up of lactic acid. These infants may develop irreversible organ damage, in particular to the brain. Umbilical cord blood gas samples should be assessed. Evidence of severe asphyxia includes a cord blood pH <7.0, Apgar score of <5 at 10 min, a delay in spontaneous respiration beyond 10 min and development of a characteristic hypoxic-ischaemic encephalopathy (HIE) with abnormal neurological signs including convulsions. Death or severe handicap occurs in more than 75% of the most severely asphyxiated term infants. Therapeutic hypothermia (cooling to 33 °C) for 72 hours may prevent secondary neuronal damage following moderate to severe asphyxia. However, for normal, well babies it is important to prevent hypothermia by careful drying and early skin-to-skin contact after birth. Preterm babies are at particular risk of hypothermia, and they should be delivered in a warm room and enclosed in clean plastic wrap before resuscitation to help maintain normothermia.
Intrauterine Growth Retardation
A baby with a birth weight below the 10th centile is small for gestational age (SGA). This may be familial or may be due to intrauterine growth retardation (IUGR). The pattern of growth retardation gives some indication of the cause. An insult in early pregnancy, such as infection, will cause symmetrical growth retardation. A later insult, usually placental insufficiency, will cause asymmetric growth retardation with relative sparing of head growth due to selective shunting of blood to the developing brain. Abnormalities of blood flow in the umbilical or fetal vessels can now be detected using Doppler ultrasound; these can be used to plan when to intervene and deliver the baby.
Causes of IUGR include:
- Multiple pregnancy
- Placental insufficiency
- Maternal smoking
- Congenital infections (e.g. toxoplasmosis, rubella)
- Genetic syndromes (e.g. Down’s syndrome).
Babies with severe IUGR should be screened for congenital infection—‘TORCH’ screen (Toxoplasmosis, Other [syphilis], Rubella, Cytomegalovirus, Hepatitis, HIV). In the first few days of life, babies with IUGR are at risk of hypoglycaemia and hypothermia due to low glycogen stores and lack of subcutaneous fat. Symptomatic hypoglycaemia can cause neurodevelopmental injury. If there has been poor head growth during pregnancy, intellect may be impaired. Babies with IUGR must not be over-fed during infancy as there is evidence that excessive weight gain leads to hypertension, ischaemic heart disease and diabetes in later life.
Vitamin K deficiency or persistent obstructive jaundice can lead to poor synthesis of vitamin K-dependent clotting factors and subsequent bleeding. The bleeding may be minor bruising or significant intracranial haemorrhage. This used to be known as haemorrhagic disease of the newborn but is now referred to as vitamin K deficiency bleeding (VKDB). Breast milk is low in vitamin K, unlike formula milk which is supplemented. For this reason vitamin K should be given routinely to all newborn infants, either as a single intramuscular injection or by mouth at birth, 1 and 6 weeks. Babies with persistent jaundice should receive further doses (see Chapter 48).
- Most babies are born healthy and do not require any resuscitation.
- The Apgar score is used to describe the condition after birth.
- Vitamin K is recommended for all babies.
- Babies with severe IUGR are at increased risk of asphyxia, hypoglycaemia and hypothermia, and may be at risk of intellectual impairment.