Critical care decisions in fetal and neonatal medicine: ethical issues
Infant survival and prevalence of low birthweight
3.3 In developed countries the number of babies who die in their first year has declined in the past 40 years (see Figure3.1 for data from England and Wales). Increased survival is likely to have arisen as a result both of general improvements in healthcare and increased standards of living, and from targeted improvements in obstetrics, midwifery and neonatal intensive care.2In England and Wales, there have been improvements in the survival rates for babies of all birthweights, particularly those classed as low birthweight (see Box3.1 and Figure3.2). The mortality rate for these babies decreased markedly between the 1960s and the late 1980s, and is continuing to fall. Despite these improvements, prematurity is still a major cause of neonatal death in the UK (Appendix 3).3
| Box 3.1: Birthweight and prematurity: definitions | |
| Length of pregnancy | |
| Full term | birth between 38 and 42 weeks of gestation |
| Premature (of preterm) | birth before 28 weeks, 0 days of gestation |
| Moderately premature | birth between 35 and 37 weeks of gestation |
| Very premature | birth between 27 and 34 weeks of gestation |
| Extremely premature | birth between 27 weeks of gestation |
| Weight | |
| Low birthweight | less than 2,500 g (5.5 lb) |
| Very low birthweight | less than 1,500 g (3.3 lb) |
| Extremely low birthweight | less than 1,000 g (2.2 lb) |
| Gestational age: In the UK, the duration of gestation is measures from the first day of the pregnan'ts woman's last menstrual period. Dates are then confirmed using ultrasound imaging in 95% of cases | |
Figure 3.1: Infant mortality rates within one year after birth in England and Wales 1960–20044
With kind permission from Professor Alison Macfarlane
Mortality rates are shown as deaths per 1,000 live births in the following periods after birth:
Early neonatal: up to six completed days
Late neonatal: between seven and 28 days
Post neonatal: between 29 days and under one year
Infant: under one year (total)
Infant mortality rates England and Wales 1960-2004
3.4 In England and Wales, the percentage of babies born with a low birthweight has gradually increased in recent years, particularly since the mid-1980s (see Figure3.3). This change has been attributed to several factors, including a trend towards registering a live birth for babies born at the limits of viability whose deaths might previously been classified as miscarriages or stillbirths, and a rise in multiple births.5Health outcomes are poorer in multiple pregnancies, irrespective of their cause.6 The increase in multiple birth rates is often attributed to the
Figure 3.2: Neonatal mortality among low birthweight babies within 28 days after birth in England and Wales 1963–2004
With kind permission from Professor Alison Macfarlane
The uppermost line shows the total rate of deaths of low birthweight babies within 28 days of birth. The section between this upper line and the middle line shows the proportion of this rate that is accounted for by babies under one day old; the section immediately below shows the proportion of this rate that is accounted for by babies who died at between one and six days old; and the lowermost section is the rate for babies who died between seven and 28 days after birth (the late neonatal period). Data collection changed in the mid-1980s when data on the rates of deaths under one day and between one and six days were combined. After this time, the section between the upper and lower lines represents the ‘early neonatal’ period. Additionally, there was also a minor change to the classification of ‘low birthweight’ babies to exclude babies of 2,500g (previously the definition was 2,500g and under). Data for the years 1989 to 1994 are unreliable because of missing birthweights.
Neonatal mortality among low birthweight babies
concomitant rise in in vitro fertility treatment since the 1980s, as there has been a tendency to implant two or more embryos. 7Although the prevalence of triplets has declined greatly over the past five years, the birth rate of twin pregnancies has stabilised. 8However, evidence that similar success rates for in vitrofertilisation may be achieved by implanting only single embryos is now available and in countries where this limit has been adopted, the rate of twinning has declined markedly. 9There have also been suggestions that the increasing tendency to delay motherhood has contributed to increases in multiple births in many developed countries, as older women are more likely to conceive multiple pregnancies than younger women.10 In addition, the UK has the highest rate of teenage pregnancy in Europe and
Figure 3.3: Incidence of low birthweight in England and Wales 1953–2004
With kind permission from Professor Alison Macfarlane
Incidence of low birthweight in England and Wales
teenagers are more likely to have a premature or low birthweight baby. 11Increasing rates of premature birth have been recorded in other developed countries, including the USA, where a recent major study identifies prematurity as “a public health problem”.12
Footnotes2 However, we note that it is difficult to link reductions in mortality with recorded changes in health provision. See Appleby J and Harrison A (2006) Spending on Health Care: How much is enough?(London: King’s Fund), pp 11–13. In one study that has been carried out in the USA, two-thirds of the decrease in neonatal mortality seen in two major hospitals in Boston in 1989–90 and 1994–5 could be attributed to improvements in neonatal intensive care, see Richardson DK, Gray JE, Gortmaker SL, Goldmann DA, Pursley DM and McCormick MC (1998) Declining severity adjusted mortality: evidence of improving neonatal intensive care Pediatrics 102: 893–9. This study was based on comparisons of neonatal outcomes in the two time periods taking into account birthweight and severity of illness on admission.
3 Confidential Enquiry into Stillbirth and Deaths in Infancy (2001) 8thAnnual Report(London: Maternal and Child Health Research Consortium).
4 Comparable recent data are available for Scotland and Northern Ireland but definitions used differ.
5 Macfarlane A and Mugford M (2000) Birth counts: Statistics of pregnancy and childbirth, 2nd Edition (London: The Stationery Office), Volume 1, p 55. From 1992 the gestation at which a stillbirth was registered rather than a miscarriage was lowered from 28 weeks to 24 weeks.
6 Marlow N (2006) Does neurodevelopment of twins and singletons differ? in Multiple Pregnancy, Kilby M, Baker P, Critchley H and Field D (Editors) (London: RCOG Press), pp 235–44.
7 Macfarlane A and Mugford M (2000) Birth Counts: Statistics of pregnancy and childbirth, 2nd Edition (London: The Stationery Office). We note that in early 2007 the Human Fertilisation and Embryology Authority (HFEA) will hold a public consultation on ways to reduce multiple births, including the transfer of single embryos.
8 National Statistics Birth Statistics(London: Office for National Statistics), Series FM1 Numbers 29–33 (2000–2004).
9 Saldeen P and Sundström P (2005) Would legislation imposing single embryo transfer to a feasible way to reduce the rate of multiple pregnancies after IVF treatment? Hum Reprod20: 4–8.
10 A biological basis for this phenomenon has recently been proposed, see Beemsterboer SN, Homburg R, Gorter NA, Schats R, Hompes PGA and Lambalk CB (2006) The paradox of declining fertility but increasing twinning rates with advancing maternal age Hum Reprod21: 1531–2.
11 Department for Education and Skills (2005) Teenage Pregnancy, available at: http://www.dfes.gov.uk/highlights/article01.shtml, accessed on: 27 July 2006; Macfarlane A and Mugford M (2000) Birth counts: Statistics of pregnancy and childbirth, 2nd Edition (London: The Stationery Office), Volume 1, p 142.
12 Institute of Medicine Committee on Understanding Premature Birth and Assuring Healthy Outcomes (2006) Preterm Birth: Causes, consequences and prevention(Washington, DC: IOM).