Elsevier

The Lancet

Volume 371, Issue 9608, 19–25 January 2008, Pages 261-269
The Lancet

Series
An overview of mortality and sequelae of preterm birth from infancy to adulthood

https://doi.org/10.1016/S0140-6736(08)60136-1Get rights and content

Summary

Survival rates have greatly improved in recent years for infants of borderline viability; however, these infants remain at risk of developing a wide array of complications, not only in the neonatal unit, but also in the long term. Morbidity is inversely related to gestational age; however, there is no gestational age, including term, that is wholly exempt. Neurodevelopmental disabilities and recurrent health problems take a toll in early childhood. Subsequently hidden disabilities such as school difficulties and behavioural problems become apparent and persist into adolescence. Reassuringly, however, most children born very preterm adjust remarkably well during their transition into adulthood. Because mortality rates have fallen, the focus for perinatal interventions is to develop strategies to reduce long-term morbidity, especially the prevention of brain injury and abnormal brain development. In addition, follow-up to middle age and beyond is warranted to identify the risks, especially for cardiovascular and metabolic disorders that are likely to be experienced by preterm survivors.

Introduction

As Goldenberg and colleagues1 outline earlier in this series, the rate of preterm birth in developed countries has risen, rather than fallen, over time. Moreover, the survival rates for very early preterm births have increased because of technological advances and the collaborative efforts of obstetricians and neonatologists. However, biologically, preterm infants are more susceptible than are their term counterparts. Although most organs are immature, the brain2 and lung3 are especially susceptible to the consequences of preterm birth, which leads to high rates of long-term neurological and health problems. Because of increasing costs of providing neonatal intensive care and social and economic burden of disabilities, the debate continues about whether intensive care is justified for infants of borderline viability. Clinicians will increasingly be exposed to survivors of preterm birth; therefore, they need to be aware of the changing outcomes and the long-term effect of disabilities and health problems on the survivors, their families, and society.

Here we review data for the mortality and both short-term and long-term sequelae of preterm birth in developed countries. The focus will be on a broad range of outcomes, such as neurodevelopment, education, behaviour, psychosocial matters, growth, and health of the most preterm (<30 or <32 weeks' gestational age) infants, at various ages from infancy through to adulthood. Whenever possible, we will add the few data available for similar outcomes in infants closer to term, sometimes referred to as late preterm births.4 For most outcomes, we will rely on the more plentiful data reported by birthweight, either for infants of very low birthweight (VLBW, birthweight <1500 g) or extremely low birthweight (ELBW, birthweight <1000 g).

The methodological issues that prevent valid comparisons of outcomes between different centres and different countries include heterogeneity of the cohorts under consideration (geographically-defined vs multicentre vs single-centre studies); reporting of outcomes by birthweight versus gestational age; varying ages of reporting outcomes; different assessment techniques; inconsistencies in the definitions and severity of reporting disabilities; and high attrition rates.5, 6

Section snippets

Late preterm births

Although preterm births at 32–36 weeks' gestation are five times more common than births before 32 weeks' gestation, their public-health effect has not been well studied.7 In 2003, 12·3% of births in the USA were preterm (defined as <37 weeks' gestation).4 What is of concern is that since 1981 there has been a 31% increase in the preterm birth rate in the USA, of which two-thirds were late preterm births (34–36 completed weeks' gestation).8

The mortality and neonatal morbidity of late preterm

Conclusions

Although work on strategies for prevention or reduction, or both, of the frequency of prematurity continues, future directions for neonatologists include modifying the antecedents of brain injury, achieving the best neonatal and postnatal care for infants, and providing greater support and resources to parents to help them achieve the best potential for their children. Additionally, further prospective long-term follow-up to middle age is warranted to establish whether preterm infants are at

Search strategy and selection criteria

In writing this review, we did a Medline search for articles reported over the past decade. We used the following medical subject headings to search for articles: “premature”, “preterm”, “low birthweight”, “follow-up”, “cerebral palsy”, and “outcomes”. We focused on studies that reported comprehensive, long-term outcomes in geographically-defined cohorts, with few or no exclusions because they are likely to be least biased.

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