Neville R Butler and Dennis G Bonham (1963) Perinatal mortality: the first report of the 1958 British Perinatal Mortality Survey under the auspices of the National Birthday Trust Fund Edinburgh: E & S Livingstone
In 1946 J W B Douglas had studied children born in one week in March (Royal College of Obstetricians and Gynaecologists, 1948) and subsequently followed up a third of the sample. In 1953 the National Birthday Trust Fund agreed to fund a similar study focusing on perinatal mortality which, after pilot studies in 1957, was carried out in 1958. This sample went on to form the basis for the National Child Development Study carried out under the auspices of the National Children’s Bureau (Davie et al., 1972).
- With over 96% of babies surviving, a healthy baby was a normal expectation.
- Only 2.4% of babies were multiple births.
- Mortality rates varied by region and social class but were lowest for second children and highest for later children.
- Mortality rates were higher among illegitimate babies and the babies of mothers over 30 years of age.
- A poor obstetric history, no prenatal care, not making a booking for a delivery or wrongly making a booking for a home or GP Unit delivery when a hospital would have been more appropriate were all associated with higher mortality rates.
- Higher mortality was associated with Rh- mothers, particularly in the absence of a Rh test or for later pregnancies.
- Various forms of toxaemia or bleeding were associated with higher mortality rates.
- Nearly half of deaths occurred before week 38 and boys were 20% more likely to die than girls.
- Curtailed pregnancies were least likely among mothers aged 25-29 and more likely below and above those ages.
- Prolonged pregnancies were more likely the younger the mother.
- Mortality was least for babies with a birth weight of 3.5-4Kg and increased exponentially the lower the birth weight below 2.5Kg.
- First children were most likely to be 2.5-3Kg and birth weight rises for later children.
- A breach delivery had the highest mortality rate and a Caesarean section the next highest; a forceps delivery had a slightly above average mortality rate.
- Respiratory distress syndrome was the most likely cause of death before 30 weeks, stillbirth in weeks 30-37, except for weeks 32-33 when congenital malformation was the most likely cause, and asphyxia or birth trauma in later weeks.
- Bookings for delivery did not reflect obstetric need.
- Socio-economic grouping, region, height of mother and number of children accounted for most of the mortality rate.
In the Foreword, W C W Nixon explains how the National Birthday Trust Fund had been founded in 1928 and how the report of the Joint Council of Midwifery had led to the 1936 Midwives Act which had created the first-ever free midwifery service. The idea for the current study had been put forward in 1953 and carried out in 1958.
In the Preface, the authors explain that, though perinatal mortality had declined from 38.5/1,000 in 1948 to 35.1/1,000 in 1958, the very normality of childbirth meant that it was difficult to get a clear idea of the problems that might affect a tiny minority of mothers and children.
In the Introduction, the authors outline the history of the survey. They collected data on every birth in the week of 3-9 March 1958 and every death in the next three months because there had been fewer than 700 deaths in the single week and they needed more data on which to base realistic conclusions. They estimated that they had had responses for 98% of the children born in 3-9 March and for 94% of the deaths in next three months.
There had been three sets of triplets in 3-9 March: in one they had all survived, in one a single baby had died and in one two had died. Multiple pregnancies involved 1.2% of the mothers and 2.4% of babies. In the March-May sample there had been fourteen sets of triplets; in six sets all the babies had died, in two one had survived and in six two had survived; there had also been one set of quads of which one baby had died. So they had decided to give results only for singleton pregnancies. This sample also included all neonatal deaths, that is, up to twenty-eight days, whereas the 3-9 March sample only included perinatal deaths, that is, up to eight days.
They had also been able to obtain the resources to undertake a pathology enquiry into all the deaths. A pilot of the study had been undertaken in Nottingham in March 1957 and of the pathology enquiry in Bristol in October 1957.
In the end, the survey had been more successful than they had expected and they had obtained more information than expected, making it impossible to analyse it all.
In Section A: Geographical region, maternal age, parity and the family social class, they report that mortality was lowest in the Eastern and Southern regions and highest in the North Western region and Wales. Mortality was lowest for the second child, six per cent higher for a first child and significantly higher for fourth and subsequent children. Mortality also varied from 69/1,000 if you were Social Class I to 128/1,000 if you were Social Class V.
Overall 4% of babies were illegitimate but their mortality rate was 159/1,000. Mortality also rose if the mother was over 30, especially among first-borns and was very high among mothers over 40. Factoring everything in, the mortality rate for the second baby of a Social Class I mother was 55/1,000 and that for a Social Class V mother having her fourth 198/1,000. However, in practice, a significant proportion of all babies were born to mothers in relative low-risk situations.
In Section B: Obstetric history, they report that a previous abortion, ectopic pregnancy, premature live birth, toxaemia, ante partum haemorrhage or Caesarean section were associated with higher risk while a previous stillbirth or neonatal death were associated with even higher risk.
In Section C: Place of delivery and perinatal care, they report that births at home or in a GP Unit had half the mortality rate of hospital births but a transfer from home or a GP Unit to hospital because of an initial wrong decision was associated with three times the mortality rate. Unbooked deliveries or those which took place outside a normal place of delivery had up to five times the mortality rate of booked deliveries at home or in a GP Unit.
Mortality was seven to ten times higher if the birth took place before week 38 and fifty per cent higher after 41 weeks. The mortality rate following a transfer was significantly higher for later children. Lower class mothers were more likely to select a home booking.
The mortality rate was five times higher where there had been no prenatal care. Mothers having their first-born were most likely to attend and mothers having a fourth or later child least likely. Mortality was least where a midwife, GP or local health authority clinic was involved but higher with hospital births because they tended to deal with more high risk cases. Midwives and local health authority clinics were more likely to deal with lower class mothers and GPs with upper class. Significantly, prenatal care by the GP alone was associated with a higher mortality rate in spite of the bias towards upper class mothers.
Most mothers seen by midwives or GPs did not have a haemoglobin test, though most of those attending a local health authority clinic and nearly all those attending hospital did. In one sixth of cases blood pressure had not been taken; GPs and midwives were most likely to omit this; it was more likely not to be taken with home confinements and most likely with unbooked confinements. The figures for Rh type testing followed a similar pattern to those for blood testing but fewer mothers had not had this test. Mortality was higher among Rh- mothers than Rh+ and was associated with not having had the test. Rh-mothers carried a higher risk of mortality than Rh+ with fourth and subsequent births.
In Section D: Toxaemia in pregnancy, they report that eclampsia increased risk by eight times, proteinuria by around two to three times, toxaemia alone by up to fifty per cent and hypertension by twenty four per cent. Toxaemia was most likely to occur in transfers from home or a GP Unit.
In Section E: Bleeding in pregnancy, they report that bleeding before the twenty-eighth week only was associated with double the mortality rate but bleeding thereafter with five times the mortality rate. There was a variety of causes, some of which were associated with the mode of delivery.
In Section F: Gestation and birth weight, they report that, though only 9.4% of babies were born before 38 weeks, they accounted for 46.2% of the deaths; mortality is lowest for weeks 40-41 and rises thereafter. Males accounted for 51.7% of the births but 55.3% of the deaths; in other words, male mortality was 20% higher.
Curtailed pregnancies were least likely to happen among mothers aged 25-29 and more likely below and above these ages; they were also least likely with the second child and more likely with later children. Prolonged pregnancies were most likely in mothers under 20; their incidence declined thereafter though less so for lower class mothers. Overall, Social Class I mothers were more likely to have a mature pregnancy than Social Class V mothers. The place of delivery was not significant for mature and prolonged pregnancies but hospitals were the worst places for curtailed pregnancies and GP Units the best.
Mortality was lowest for babies with a 3.5-4Kg birth weight and next lowest for babies with a 3-3.5Kg birth-weight. Babies with birth-weights of less than 2.5Kg had exponentially higher mortality the lower the birth-weight. As birth-weight rises with the mother’s age, first children are most likely to be 2.5-3Kg. However, both class and place of delivery are more significant for mortality than birth-weight though ‘large for dates’ premature babies have lower mortality even though it is higher than for a full-term baby; low birth-weight is still a significant factor for full-term babies.
In Section G: Labour and delivery, they report that breech births have the highest mortality rate, especially among low birth-weight babies; a Caesarean section has the next highest mortality rate while a forceps delivery has a mortality rate only slightly higher than average.
Midwives and pupil midwives carried out most deliveries with a midwife being the most senior person at seventy per cent of deliveries.
The first stage of labour had a modal length of 12-24 hours for first-borns; mortality increased by a fifth if this stage exceeded 24 hours and doubled if it exceeded 48; for later-borns this stage had a modal length of 6-12 hours.
The second stage of labour had a modal length of 90-120 minutes for first-borns and 30-60 minutes for later-born babies.
Forceps delivery was best when protecting the head of a small baby while Caesarean section was a much better option than forceps or breach for large babies. Interestingly, babies delivered at night with a forceps delivery, breech delivery or Caesarean section had a lower mortality rate than those delivered during the day.
In Section H: General analysis of deaths, the authors summarise the deaths that occurred in the 3-9 March sample. Of the 369 stillbirths, 195 perinatal deaths and 54 neonatal deaths, 16.6% involved congenital malformations, 22.2% an ante partum stillbirth, 33.2% asphyxia or a birth trauma, 12.2% respiratory distress syndrome (RDS) and 5% an infection.
In Section I: Post-mortem findings, March 1958, they report that low birth-weight was associated with most deaths but especially those as a result of RDS; babies suffering from a congenital malformation and infection were most likely to die towards the end of the first week.
In Section J: Clinico-pathological associations, March 1958, they report that there were considerable regional variations but that mortality was
- second children
- SCI & SCII
- home/GP Unit booked deliveries
- fifth and later children
- SCIV & SCV
- hospital transfers
Mortality was associated with toxaemia, bleeding and length of gestation with RDS most likely as a cause of death before 30 weeks. Congenital malformation was the most likely cause of death in weeks 32-33, with stillbirth the most likely cause in the other weeks from 30-37. Asphyxia or birth trauma was most likely to be the cause of death in later weeks.
Death was also associated with birth-weight and method of delivery and, except for congenital malformations, more boys died than girls.
In Section K: Social correlations of perinatal mortality, the authors note that social class differences had widened between 1950 and 1958 but standardising the results for age and parity made no difference to the social class differences. Mortality was lowest in the South Eastern region and highest in the North Western region, Wales and Scotland. Moreover, while the composition of social classes varied between the regions, the class differences remained within the regions.
The pattern of bookings for delivery did not correlate with obstetric need. Also, taller women, who generally have lower mortality, are more likely to be found in higher social classes or the south.
In other words the four factors, socio-economic grouping, region, height and number of children, account for most of the mortality rate. Overall, the study had shown that there is greater variation than is often accepted and that social class disparities continue, in part because mothers’ experiences are not just confined to pregnancy. Furthermore, if a mother changes social class, the mortality rate for her babies also changes.
In Section L: Summary, they summarise the findings in the earlier chapters.
This study is one of the first beneficiaries of the computer age. Though J W B Douglas (Royal College of Obstetricians and Gynaecologists, 1948) had undertaken a comprehensive study of one week’s births in 1946, the need to analyse the data by hand limited the number of associations that could be studied. Even with the primitive computers of the 1950s, the scope for working out complex statistical correlations had greatly expanded and, even though the designers of the study almost certainly over-estimated how much data they could handle, the fact that they collected it has meant that it has been available for later researchers to use as computers have become more powerful and more capable to handling large volumes of data.
It also followed in the great tradition of Alfred Binet (1903) in studying the normal in order to understand variation, a factor which came to have particular significance when Fogelman (1976) was able to show that, for most young people, adolescence is not a period a ‘storm and stress’ but rather one of relatively smooth transition. Hitherto, those who had studied the small proportion of young people who had difficulties had incorrectly generalised their findings to all young people.
But, for a generation that had just settled down to the idea of a free and easily accessible National Health Service, it brought an uncomfortable message that social class divisions continued to impact on children’s life chances and that these divisions were widening rather than narrowing. While it may not have set the agenda, it almost certainly fed into 1960s social policy and political agendas.
Binet, A (1903) L’étude expérimentale de l’intelligence Paris: Schleicher Frères et Cie
Davie, R, Butler, N R and Goldstein, H (1972) From birth to seven: the second report of the National Child Development Study (1958 Cohort) London: Longmans
Fogelman, K (1976) Britain’s sixteen year olds: preliminary findings from the third follow-up study of the National Child Development Study (1958 Cohort) London: National Children’s Bureau
Royal College of Obstetricians and Gynaecologists (1948) Maternity in Great Britain: a survey of social and economic aspects of pregnancy and childbirth undertaken by a Joint Committee of the Royal College . . . and the Population Investigation Committee London: Oxford University Press