a Department of Epidemiology, Social Medicine and Health System Research, Hanover Medical School, Hanover, Germany.
b Department of Perinatology, Isala Clinics, Zwolle, The Netherlands.
c Clara Angela Foundation, Witten, Germany.
Elke Raum, Department of Epidemiology, Social Medicine and Health System Research, OE 5410, Hanover Medical School, 30623 Hanover, Germany. E-mail: raum{at}epi.mh-hannover.de
Abstract
Background Objective of this re-analysis of datasets from former East and West Germany was to examine the influence of maternal education on intrauterine growth in two different political and social systems.
Methods Information on socio-demographic or lifestyle factors and pregnancy outcome was available for 3374 liveborn singletons from West Germany (1987/88) and 3070 from East Germany (1990/91). Multiple logistic regression was used to estimate the association between maternal education and the risk of delivering a small-for-gestational-age (SGA) newborn below the 10th percentile of birthweight.
Results Women with the lowest education had a significantly elevated risk of SGA newborns compared to women with the highest education in West (odds ratio [OR] = 2.58, 95% CI : 1.175.67) and East Germany (OR = 2.77, 95% CI : 1.54 5.00). The distribution of factors known to influence intrauterine growth varied with education in both states. After adjusting for these factors, women with the lowest educational level still had a higher risk of SGA birth: OR (West) = 2.02, 95% CI : 0.874.72; OR (East) = 1.95, 95% CI : 1.023.74.
Conclusions Our findings support the assumption that in former socialist countries health inequalities as a result of social inequalities existed.
KEY MESSAGES
Keywords Germany, epidemiology, educational status, pregnancy outcome, infant, low birthweight
Accepted 30 August 2000
Ten years after the German reunification, the long-term effects of more than 40 years of separation are still noticeable and not completely overcome. The former Federal Republic of Germany was a democratic Western country with a high level of social security and easy access to high-quality medical care. The former German Democratic Republic as a socialist country can be characterized by a relatively equal distribution of resources and living conditions. In comparison with industrialized Western countries there was a considerably lower overall variance in income.1 Equal access to health care and an accentuation of health prevention were characteristics of the East German health care system. Prenatal care was differently organized in both German states: Whereas in West Germany prenatal care was voluntary and decentralized, it was mandatory and highly centralized in East Germany. Prevention of disease was more emphasized by the East German prenatal care system compared to the West German.2 Pregnant women were better supported at their work places as the great majority of women in East Germany were working. Families received extra financial support.3 But despite the uniform lifestyle and less disparate income levels, social stratification in former socialist countries existed and was reflected by inequalities regarding health status.4,5 In industrialized democratic Western countries differences in pregnancy outcomes, like preterm delivery, low birthweight or intrauterine growth retardation are related to social class.69 Little is known about the distribution of adverse pregnancy outcomes, particularly between social groups in former countries of Eastern Europe.10,11
Poor intrauterine growth not only reflects maternal health and health behaviour but is also a predictor for perinatal and neonatal mortality and morbidity and determines human susceptibility to disease and quality of life later on.12,13
We therefore chose small-for-gestational-age (SGA) newborns to test the hypotheses: (1) that different educational levels in both former German states were associated with certain risk profiles for SGA babies and (2) that an association between SGA babies and maternal education existed for both former parts of Germany which had comparable ethnic populations but different political, social and health care systems.
Material and Methods
In West Germany, the original study was conducted by Infratest Epidemiology and Health Research (Incorp.), Munich, on behalf of the Federal Office for Radiation Protection. From a total of 5200 obstetricians seeing pregnant women for regular ambulatory prenatal care in their practices in West Germany, 1000 obstetricians were randomly drawn and 591 agreed to participate in this study. Each obstetrician was requested to prospectively recruit 10 women during regular prenatal checks. From August 1987 until May 1988, 3946 pregnant women returned questionnaires. Certain federal states were slightly overrepresented to allow for subgroup analyses. Data on pregnancy and delivery outcome were available for 3418 women (86.6%). After exclusion of stillbirths and multiple pregnancies, data from 3374 liveborn singletons (85.5%) could be analysed.
The study in East Germany was also conducted by Infratest Burke, Munich, Germany. In former East Germany, pregnant women were assigned to certain outpatient prenatal care clinics according to their residential zip code. Eight hospitals with their adjunct outpatient clinics participated in this study. At the beginning of the study all pregnant women currently receiving care and during the study all newly pregnant women were asked to participate. From May 1990 to January 1991, a total of 4043 pregnant women returned questionnaires. Data on pregnancy outcome were available for 3113 women (77.0%). After exclusion of stillbirths and multiple pregnancies, data on 3070 liveborn singletons (75.9%) could be analysed.
Women were recruited during pregnancy and given a self-administered 30-page questionnaire to be completed during pregnancy. This questionnaire covered sociodemographic, psychosocial, nutritional, environmental, and occupational factors. In West Germany, information on pregnancy outcome was obtained by the office-based obstetricians 4 to 6 weeks after delivery from the maternity certificate (Mutterpass), where routine prenatal and perinatal data are documented during pregnancy and after delivery. In East Germany, the obstetricians at the participating obstetric centres completed standardized documentation sheets to record prenatal and perinatal data immediately after delivery.
Age at delivery was calculated from maternal date of birth and date of birth of the child. Mothers were stratified into four categories on the basis of their self-reported smoking habits when completing the questionnaire: non-smokers, smoking 5 cigarettes per day, >5 cigarettes per day and those smoking an unknown number of cigarettes per day. Pregravid body mass index (BMI) was calculated using information from the maternal questionnaire by dividing pregravid maternal weight (in kg) by maternal height squared (in m2) and categorized into three groups: low (<19.8 kg/m2), normal (19.826.0 kg/m2) and high (>26.0 kg/m2). Maternal height was grouped into three categories:
160, 161170 and >170 cm. Information on marital status was also obtained from the maternal questionnaire. Information on parity was obtained from the maternity certificate or the standardized documentation sheet: women were stratified as nulli-, primi- or multiparous. The same sources were used for information on the number of prenatal care visits and on gestational week of first prenatal care visit.
Data on maternal education were obtained from the maternal questionnaire. The school systems of the two German states were not identical and can therefore not be compared directly. For each country maternal education was reduced to five categories. Women who stated they had not completed a certain educational level (e.g. not completed university) were included into the next lower completed level. The lowest category was 8 years of education and the highest was a university degree in both parts of Germany. The other categories of educational level are shown in Table 1
.
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For dichotomizing SGA, the same sex-specific cut-off points (10th percentile of birthweight from 24 through 43 weeks) were used for both countries. We applied the standards calculated by Voigt et al.14 for 563 480 German singleton deliveries (East and West) in 1992.
Statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) version 8.0. Prevalences of exposure and outcome variables were compared between West and East Germany and between educational levels of both states using 2 tests for categorical data. Wilcoxon rank sum tests and Kruskal-Wallis test were used for continuous data. Two-tailed P-values <0.05 were considered to indicate statistical significance. Crude and adjusted odds ratios (OR) and their corresponding 95% CI were calculated by unconditional logistic regression as measures of association. As reference group, the highest educational level (university degree) was used in both parts of Germany. Missing data were handled as a separate category in the analyses (results not shown). Factors which are known to influence intrauterine growth were selected a priori and their potential effects on the association between educational level and SGA births were assessed in bivariate models including each covariate separately. Adjustment for federal state or nationality did not alter the bivariate or adjusted OR substantially (<10%) and were therefore not included in the models. To test for trend, the educational levels were included as interval-scaled variables in the regression model.
Additionally, we calculated a relative index of inequality (RII)1517 because relatively small groups at the margins of the hierarchy may lead to a finer discrimination of the extreme educational categories and therefore larger ratios.17 The RII assigns a value between 0 and 1 to each educational category according to the proportion of participants with a higher position than the midpoint of each group within the hierarchy. Since the outcome parameter was dichotomous unconditional logistic regression was applied. The interpretation of this measure is the odds of delivering an SGA infant for those at the bottom of the educational hierarchy compared to those at the top. More details about the index can be found elsewhere.1517
Results
The overall prevalence of SGA babies did not differ significantly between West (9.5%) and East Germany (10.8%) (Table 2). East German mothers were significantly younger than mothers from West Germany. Only 7.7% of pregnant women from East and 2.7% from West Germany had an educational level of
8 years. The prevalence of women with a university degree differed only marginally: 8.6% (East) and 7.4% (West). In West Germany, almost 90% of women were married, in East Germany only 56.9%. More women from West Germany (20.6%) were smokers during pregnancy; only 12.6% of women smoked in East Germany. There were significantly more nulliparous women in East (61.1%) than in West Germany (48.9%). In West Germany only 12.2% of women had their first prenatal visit after the first trimester and 21.9% had less then 10 visits, in East Germany almost one-third had their first visit after the first trimester but only 15.2% had less than 10 visits (Table 2
).
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Women with the lowest educational level had a significantly higher risk of delivering a SGA baby compared to women with the highest level in West (unadjusted OR = 2.58, 95% CI : 1.17 5.67) and East Germany (unadjusted OR = 2.77, 95% CI : 1.54 5.00, Table 5).
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Concomitant adjustment for all variables with the exception of number of prenatal care visits and gestational week of first prenatal care visit led to an overall decrease in the magnitude of the association between maternal education and an SGA newborn, but still resulted in a twofold higher risk for women in the lowest educational level compared with women of the highest level (adjusted OR (West) = 2.02, 95% CI : 0.874.72; adjusted OR (East) = 1.95, 95% CI : 1.023.74). For East Germany the trend was still significant (Table 5).
The RII for SGA-infants were 1.54 (95% CI : 0.982.40) in West Germany and 2.50 (95% CI : 1.583.94) for East Germany.
Discussion
The objective of this analysis was to examine if there was an association between maternal education and SGA births in former East Germany, and to compare the findings with data from West Germany. The data in East Germany were collected in 1990/91 before and shortly after the reunification when the social and political background of pregnant women still was highly influenced by the former political and social system. Reference data from West Germany were collected in 1987/88.
Several potential sources of bias have to be considered. Out of 1000 obstetricians, 591 agreed to participate and recruit pregnant women, resulting in a response rate of 60% of doctors. Infratest expected a response rate of 67% of women, some 4000 questionnaires, a number which was closely met by returned questionnaires (3946). We have no information about doctors or women not participating. Utilization of prenatal care is high in West Germany and the great majority of women consult obstetricians. When comparing certain variables with representative studies, we found an almost identical prevalence of smoking during pregnancy (20%);18 and the prevalence of SGA infants in our study closely reflects the expected 10%.
The eight obstetric hospitals participating in East Germany with their adjunct prenatal care centres were not randomly chosen but primarily selected by willingness to participate in this study. Therefore women in the later established new federal state of Brandenburg were not included. Nevertheless, those territorial structures did not exist in the former German Democratic Republic, and East German women were assigned according to their residential postcodes to their prenatal care centres. Registration at prenatal care centres in East Germany was almost complete.19 From the originally distributed 5698 questionnaires a total of 4043 were returned to Infratest. We do not know how many women received care at the participating prenatal care centres during that time nor how many women refused to participate. Due to the political changes which were taking place during this time in East Germany, the percentage of available pregnancy and delivery data was somewhat lower than in West Germany (77%), but as in West Germany comparison of certain variables with representative data revealed no major selection bias: The rate of preterm births in Brandenburg (5.8% in 1990)20 was comparable to the prevalence of preterm birth in our study (5.7%). Official statistics show a comparable percentage of newborns born out of wedlock (35% in 1990 and 42% in 1991).21 The prevalence of SGA infants closely reflects the expected 10%.
For variables like smoking, height, pregravid weight or education, the self-reported information given in the questionnaire was used. Smoking habits were assessed when the questionnaires were completed. According to Fingerhut et al.,22 the majority of women who smoke and quit smoking due to being pregnant, do quit when they find out that they are pregnant. We found an almost identical prevalence of smoking during pregnancy (20%) compared to Helmert et al.18
We also used self-reported height and pregravid weight. Information on pregravid weight was only available from questionnaires. Maternal height was also documented in the maternity certificates (West Germany) and the standardized documentation sheets (East Germany). There might be a potential bias by using self-reported data with height being overreported and weight being underreported and a social gradient for this bias has to be taken into account. Therefore we calculated the difference between self-reported height and documented height and compared these differences between the different educational categories and found no significant differences.
In conclusion, there are no hints that a strong selection or information bias is operating, which might heavily influence the association between maternal education and SGA births.
Income differences were relatively small in the former German Democratic Republic and resources and access to health care were equally distributed. Nonetheless, higher education seems to have ensured better living and working conditions. Furthermore, achieving a medium level of education was one of the priorities of socialist policy. East Germans who did not achieve this standard presumably belonged to a distinct social group. As a consequence, it can be assumed that social inequalities in the former socialist countries still existed and had an impact on the distribution of different health parameters.4,5
In our study, maternal education was associated with the risk of SGA delivery in East and West Germany. In both, women belonging to the lowest category of education had an unadjusted relative risk of 2.5 for delivering an SGA baby compared with women in the highest category.
A major component of the observed effects of maternal education in both states was attributable to sociodemographic and lifestyle factors. In our study, the prevalence of smoking among pregnant women was strongly related to maternal education in both states, and comparable to other studies.23 Additional adjustment for smoking alone reduced the magnitude of the observed association substantially. Also for other risk factors of intrauterine growth retardation we could prove a relation with maternal education in both countries: maternal age, maternal body height, marital status. Nevertheless women with low education also have an increased prevalence of some factors which prevent SGA newborns such as high BMI or higher parity. Interestingly, no significant differences in parity for the different educational levels were found in East Germany. This was probably a result of East German family policy. With regard to prenatal care utilization, measured by number of prenatal visits and gestational week of first visit, we observed distinct patterns depending on maternal education for both states: Less educated mothers had less prenatal care visits and started their visits to prenatal care later. Nevertheless, these differences had no influence upon the association between maternal education and SGA newborns.
Maternal education as an indicator for socioeconomic status might therefore reflect a constellation of influencing factors which are unique for particular groups and might stand for differences in the utilization of the health care system and better knowledge of health-related behaviour. It should be possible to differentiate mothers and their susceptibility to adverse pregnancy outcomes by their educational level.24
Adjustment for these known factors reduced the magnitude of the observed association to some extent, but could not fully explain the impact of maternal education since a effect can still be observed. As expected, the relative index of inequality, measuring the total size of differences that are related to educational inequality, was somewhat smaller, especially in West Germany, which might be caused by the small groups at the margin of the educational hierarchy.
Our results for West Germany are in accordance with studies from other Western countries.6,7,25,26 In the US, Parker et al.27 found that white American women with the lowest level of maternal education had almost twice the odds of delivering an SGA newborn compared to mothers in the highest category.
There are only few studies comparing pregnancy outcomes between former socialist and democratic countries. Koupilová et al.28 found, when comparing the Czech Republic, a former socialist country, with Sweden, that there was also a birthweight gradient for maternal education within the Czech Republic: The mean difference in birthweight between women with primary and university education was almost 115 g. In Sweden, a difference between these two educational categories was less pronounced (mean: 89 g).
In conclusion, maternal education distinguished between particular social groups not only in West but also in East Germany, a former socialist country, and had an impact on pregnancy outcomes.
Most of those former socialist states now have different political and health care systems. Koupilová et al. found10 that in the Czech Republic there was a slight overall increase in birthweight since 1991, but this increase was not observed in the lowest educational category. This consequently led to a widening of differences in birthweight between educational levels. An observation which was also made for Estonia, another former socialist country.29 We do not know if this trend would have also been seen in former East Germany because reunification led to different social and political development in comparison with other former socialist countries. To answer this question, further research is needed.
Acknowledgments
This study was funded exclusively by the Federal Ministry of Education, Research and Technology (01EG9511).
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