1061
Better Perinatal Health BACKGROUND TO PERINATAL HEALTH GEOFFREY CHAMBERLAIN
Queen Charlotte’s Maternity Hospital, London THE articles in this series will be about perinatal health-that is, about health from the 28th week of gestation to the end of the first week of life-and the usual measure will be the perinatal mortality rate per thousand stillbirths and live births (PNMR). It may seem strange that death rates are used to measure their converse, continuing health, and in the next article Dr lain Chalmers will discuss some alternative approaches. At present there are two cogent reasons for favouring PNMR. Firstly, death is a finite event, which unlike illness can be recorded with equal certainty in different parts of the world. Hence mortality statistics are more exact than morbidity ones. Secondly, the cause of death is often diagnosed with greater accuracy than is the reason for any morbidity, partly owing to the high necropsy rate in those who die in the perinatal period, and partly owing to the smaller number of possible diagnoses.
1933 38
43
48
53
58
63
68
73
78
YEARS
Fig.
I—PNMRs for
England
&
Wales 1933-78.
From Macfarlane.’
Some British exponents of perinatal-health data draw attention to the higher spending of other countries on obstetric services and relate this causally to the lower rates of perinatal mortality in these countries. If gross domestic products and the proportion of them spent on health (the only relevant data available for many coun-
TRENDS IN THE UNITED KINGDOM
1 shows the PNMR in the U.K. over the past 40 a plateau after the 1939-45 war the decline is almost steady. More importantly, MacFarlane’ has pointed out that the percentage reduction of mortality in England and Wales is much greater in the past 5 years than in any similar period since 1931. This sharp fall in PNMR would be hard to account for on demographic grounds alone: from the improvements in nutrition and education one would expect a more general and gradual reduction. Perhaps it results from some change in obstetric practice-more hospital deliveries, increased antenatal care, more intensive management in labour-but there is no proof at the
Fig.
years.
Apart from
moment.
Fig. 2-PNMRs in various countries for 1975. &Dgr; 1974 data; 0 26 weeks gestation and above only; 0 28 weeks gestation and above only. From On the State of the Public Health. H.M. Stationery Office, 1977.
INTERNATIONAL COMPARISONS
The United Kingdom is often said to be falling behind other countries in its perinatal services (see fig. 2), and published PNMR data do show a slower decline in the U.K. than in many other countries. Such comparisons must be handled cautiously, because not all the differences will be attributable to deficiencies in obstetric services. One country may have a healthier population than another, or there may be a different pattern of reproduction, with women having their babies earlier. The rates of background variables may differ: for example, the incidence of anencephaly in France is one third that in England, while the rate of low birthweight in Sweden is a quarter that in Hungary. In addition to these biological variations, there may be differences in data collecting methods. Some countries do not count live babies born before a certain time of gestation or below a certain birthweight (see fig. 2).
3000
5000
7000
9000
GDP per caput in$
Fig. 3—PNMRs for the countries in fig. 2 by gross domestic product in$for 1975 (r=-0.64). From On the State of the Public Health. H.M. Stationery Office, 1977; and Year Book of National Accounts Statistics. United Nations, 1978.
1062
plotted against perinatal mortality, the relation is not very close. If health expenditure is plotted as a proportion of per caput income a much clearer relation emerges. But this index reflects a country’s background prosperity, and perinatal mortality seems related less to expenditure on formal health services than to the total way of living (see fig. 3). Standards of living and nutrition are very important factors, and any impact attributed to changes in obstetric services must be seen against this background.
tries)
are
O 0
z
1 PARITY
1
4
2&3
Fig. 5-PNMRs for United Kingdom in 1970, by parity. THE ASSOCIATES OF PERINATAL MORTALITY
perinatal mortality major are congenital abnormalities, low birthweight, and hypoxia. They are associated with three-quarters of perinatal mortality and a similar proportion of morbidity; other important xtiological factors are birth injuries, infection, and hasmolytic disease. Some congenital abnormalities are being diagnosed antenatally, whereupon the fetus is
From Chamberlain et al.2
determinants of
The three
removed, but the real attack
must come from factor and teratogenic finding excluding it. Low result from spontaneous premature birthweight may delivery, intrauterine growth retardation, or induced delivery. In the U.K. the proportion of children with birthweights below 2500 g has remained constant for 30 years-it was 6.4% in 1946 and 6.9% in 1970.2 Hypoxia may arise antenatally but it is more common and more easily prevented in labour. These factors in perinatal mortality will be discussed in later articles.
the
THE CLASSIC TRIAD
Three maternal background factors are classically associated with perinatal mortality-age, parity, and socioeconomic class.
Age 4 shows the typical effect of age. The reasons for the rates at the extremes of reproductive life are, briefly, that older women may be at higher risk of intercurrent disease such as hypertension, while young women are likely to be unmarried or having their first baby. Commonly such groups seek and respond to antenatal care less readily.
Fig. higher
Parity The distribution of perinatal mortality by parity is not dissimilar from that by age and to some extent they are linked (fig. 5). The higher risk of a first pregnancy includes problems
such as the fit of the baby in the pelvis and the higher incidence of pre-eclampsia. The blood-supply to the placental bed may also be less in the first pregnancy than in later ones. Alberman et al.,4 in a cross-sectional study of women doctors, found that birthweight in a second pregnancy was above the average for a first pregnancy even in those whose first had ended in abortion.
Socioeconomic Class The Registrar General’s classification is based upon the occupation of the husband, from professional (I) to unskilled (V). In the case of illegitimate births there is no husband and so such mothers are usually grouped together (as in fig. 6). The wives of students, of the unemployed, and of people in the Armed Forces are not classified. Fig. 6, from the British Births Survey (1970),1 shows the steep rise in PNMR from social class I to social class V and emphasises the even worse figures for unmarried women. Women tend to marry into their own socioeconomic class and the differences in perinatal mortality rates reflect the woman’s biological background-past diseases, education, and attitudes as well as nutrition and current financial state. It is difficult to identify the factors in social class which lead to higher PNMRs but physical features, such as the greater height of women in social class I, may well be relevant. The social-class gradient is seen in all age and parity groups.
investigations on this triad have been cross-sectional, relying on data taken from a population at one time. On the evidence of longitudinal studies, in which a cohort of women are followed through their reproductive years, some of the conclusions on age, parity, and social class may have been wrongly drawn. For example, Bakketeig and Hoffman5 described recently a large population-based longitudinal study in Norway where PNMR decreased steadily with parity in all maternal age-groups. For a given birth order, PNMR was higher in babies born into the larger families, and Most of the
Better Perinatal Health BACKGROUND TO PERINATAL HEALTH GEOFFREY CHAMBERLAIN
Queen Charlotte’s Maternity Hospital, London THE articles in this series will be about perinatal health-that is, about health from the 28th week of gestation to the end of the first week of life-and the usual measure will be the perinatal mortality rate per thousand stillbirths and live births (PNMR). It may seem strange that death rates are used to measure their converse, continuing health, and in the next article Dr lain Chalmers will discuss some alternative approaches. At present there are two cogent reasons for favouring PNMR. Firstly, death is a finite event, which unlike illness can be recorded with equal certainty in different parts of the world. Hence mortality statistics are more exact than morbidity ones. Secondly, the cause of death is often diagnosed with greater accuracy than is the reason for any morbidity, partly owing to the high necropsy rate in those who die in the perinatal period, and partly owing to the smaller number of possible diagnoses.
1933 38
43
48
53
58
63
68
73
78
YEARS
Fig.
I—PNMRs for
England
&
Wales 1933-78.
From Macfarlane.’
Some British exponents of perinatal-health data draw attention to the higher spending of other countries on obstetric services and relate this causally to the lower rates of perinatal mortality in these countries. If gross domestic products and the proportion of them spent on health (the only relevant data available for many coun-
TRENDS IN THE UNITED KINGDOM
1 shows the PNMR in the U.K. over the past 40 a plateau after the 1939-45 war the decline is almost steady. More importantly, MacFarlane’ has pointed out that the percentage reduction of mortality in England and Wales is much greater in the past 5 years than in any similar period since 1931. This sharp fall in PNMR would be hard to account for on demographic grounds alone: from the improvements in nutrition and education one would expect a more general and gradual reduction. Perhaps it results from some change in obstetric practice-more hospital deliveries, increased antenatal care, more intensive management in labour-but there is no proof at the
Fig.
years.
Apart from
moment.
Fig. 2-PNMRs in various countries for 1975. &Dgr; 1974 data; 0 26 weeks gestation and above only; 0 28 weeks gestation and above only. From On the State of the Public Health. H.M. Stationery Office, 1977.
INTERNATIONAL COMPARISONS
The United Kingdom is often said to be falling behind other countries in its perinatal services (see fig. 2), and published PNMR data do show a slower decline in the U.K. than in many other countries. Such comparisons must be handled cautiously, because not all the differences will be attributable to deficiencies in obstetric services. One country may have a healthier population than another, or there may be a different pattern of reproduction, with women having their babies earlier. The rates of background variables may differ: for example, the incidence of anencephaly in France is one third that in England, while the rate of low birthweight in Sweden is a quarter that in Hungary. In addition to these biological variations, there may be differences in data collecting methods. Some countries do not count live babies born before a certain time of gestation or below a certain birthweight (see fig. 2).
3000
5000
7000
9000
GDP per caput in$
Fig. 3—PNMRs for the countries in fig. 2 by gross domestic product in$for 1975 (r=-0.64). From On the State of the Public Health. H.M. Stationery Office, 1977; and Year Book of National Accounts Statistics. United Nations, 1978.
1062
plotted against perinatal mortality, the relation is not very close. If health expenditure is plotted as a proportion of per caput income a much clearer relation emerges. But this index reflects a country’s background prosperity, and perinatal mortality seems related less to expenditure on formal health services than to the total way of living (see fig. 3). Standards of living and nutrition are very important factors, and any impact attributed to changes in obstetric services must be seen against this background.
tries)
are
O 0
z
1 PARITY
1
4
2&3
Fig. 5-PNMRs for United Kingdom in 1970, by parity. THE ASSOCIATES OF PERINATAL MORTALITY
perinatal mortality major are congenital abnormalities, low birthweight, and hypoxia. They are associated with three-quarters of perinatal mortality and a similar proportion of morbidity; other important xtiological factors are birth injuries, infection, and hasmolytic disease. Some congenital abnormalities are being diagnosed antenatally, whereupon the fetus is
From Chamberlain et al.2
determinants of
The three
removed, but the real attack
must come from factor and teratogenic finding excluding it. Low result from spontaneous premature birthweight may delivery, intrauterine growth retardation, or induced delivery. In the U.K. the proportion of children with birthweights below 2500 g has remained constant for 30 years-it was 6.4% in 1946 and 6.9% in 1970.2 Hypoxia may arise antenatally but it is more common and more easily prevented in labour. These factors in perinatal mortality will be discussed in later articles.
the
THE CLASSIC TRIAD
Three maternal background factors are classically associated with perinatal mortality-age, parity, and socioeconomic class.
Age 4 shows the typical effect of age. The reasons for the rates at the extremes of reproductive life are, briefly, that older women may be at higher risk of intercurrent disease such as hypertension, while young women are likely to be unmarried or having their first baby. Commonly such groups seek and respond to antenatal care less readily.
Fig. higher
Parity The distribution of perinatal mortality by parity is not dissimilar from that by age and to some extent they are linked (fig. 5). The higher risk of a first pregnancy includes problems
such as the fit of the baby in the pelvis and the higher incidence of pre-eclampsia. The blood-supply to the placental bed may also be less in the first pregnancy than in later ones. Alberman et al.,4 in a cross-sectional study of women doctors, found that birthweight in a second pregnancy was above the average for a first pregnancy even in those whose first had ended in abortion.
Socioeconomic Class The Registrar General’s classification is based upon the occupation of the husband, from professional (I) to unskilled (V). In the case of illegitimate births there is no husband and so such mothers are usually grouped together (as in fig. 6). The wives of students, of the unemployed, and of people in the Armed Forces are not classified. Fig. 6, from the British Births Survey (1970),1 shows the steep rise in PNMR from social class I to social class V and emphasises the even worse figures for unmarried women. Women tend to marry into their own socioeconomic class and the differences in perinatal mortality rates reflect the woman’s biological background-past diseases, education, and attitudes as well as nutrition and current financial state. It is difficult to identify the factors in social class which lead to higher PNMRs but physical features, such as the greater height of women in social class I, may well be relevant. The social-class gradient is seen in all age and parity groups.
investigations on this triad have been cross-sectional, relying on data taken from a population at one time. On the evidence of longitudinal studies, in which a cohort of women are followed through their reproductive years, some of the conclusions on age, parity, and social class may have been wrongly drawn. For example, Bakketeig and Hoffman5 described recently a large population-based longitudinal study in Norway where PNMR decreased steadily with parity in all maternal age-groups. For a given birth order, PNMR was higher in babies born into the larger families, and Most of the
