Chapter 9 Neonates
The earliest in pregnancy at which newborn babies can sometimes survive is around 23 weeks’ gestation, when survival is about 10% for liveborn babies. Conventionally, any baby born at less than 32 weeks is regarded as being at relatively high risk of death or disability. About 7.5% of all births are technically ‘premature’ (<37 weeks) but only 1.4% of births take place before 32 weeks of gestation. Likewise, 7% of all babies are low birth weight (LBW), for example, <2500 g, and 1.4% are very low birth weight (VLBW). However, it is the gestation at birth rather than the birth weight which is of more practical and prognostic value. The definitions of selected terms used for babies are given in Table 9.1.
Normal length of human pregnancy (term) | 37 up to 42 completed weeks of gestation |
Preterm | <37 weeks of gestation at birth |
Post-term | 42 completed weeks onwards |
Neonatal period | Up to the 28th postnatal day |
Low birth weight (LBW) | <2500 g |
Very low birth weight (VLBW) | <1500 g |
Extremely low birth weight (ELBW) | <1000 g |
Major clinical disorders
Respiratory distress syndrome (RDS)
Similarly, the introduction of exogenous surfactant, derived from the pig or calf, has revolutionised the management of RDS. Natural surfactants derived from animals are currently more effective than artificial synthetic ones. The first dose should be given as soon as possible after birth since the earlier it is given, the greater the benefit (Soll, 1999).
There are several other important ways of treating babies in respiratory failure. Inhaled nitric oxide dilates pulmonary arterioles and lowers the excessive pulmonary blood pressure which often complicates respiratory failure. Persistent pulmonary hypertension may also complicate early onset septicaemia and meconium aspiration syndrome; in term and near-term babies, nitric oxide is both more effective than the previous drug therapies and much less likely to lead to systemic hypotension. However, it does not reduce mortality or major complications when used in babies with birth weights less than 1500 g (Van Meurs et al., 2005).
For some babies of at least 34 weeks of gestation and at least 2 kg birth weight, extracorporeal membrane oxygenation (ECMO), in which a baby is in effect put on partial heart–lung bypass for a few days, may be life-saving when ventilation and nitric oxide fails (ECMO Collaborative Trial Group., 1996).