TY - JOUR
AU - Leon, David, A
AB - Abstract Background To investigate social variation in birthweight and length of gestation in Estonia in the period of transition to a democracy and market economy. Methods All live births resulting from singleton pregnancies reported to the Estonian Medical Birth Registry in 1992–1997 (n = 84 629) were studied with respect to social variation in birthweight and preterm delivery (<37 weeks gestation). The results were adjusted for maternal age, parity, education, nationality, marital status, smoking in pregnancy, sex of the infant (and gestational age). Results Between 1992 and 1997, mean birthweight increased from 3465 g to 3497 g (P < 0.001) and the preterm rate fell from 5.8% to 5.1% (P = 0.001). Maternal education, marital status and nationality were all independently related to the mean birthweight and the risk of preterm birth. The mean difference in birthweight between children of mothers with basic and university education was 87 g (95% CI : 74–100). Children born to mothers of non-Estonian compared to Estonian nationality were on average 77 g lighter (95% CI : 70–84). While the effect of nationality and marital status on birthweight was relatively stable during the study period, differences in birth outcome by maternal education became stronger. Conclusions The mean birthweight increased and the preterm rate decreased in Estonia as a whole during the transition. However, the improvements were not shared equally by all social groups. An increase in variation in birthweight by maternal education was particularly notable. Birthweight, preterm birth, socioeconomic factors, health inequalities, Estonia In the late 1980s and early 1990s, all the former socialist countries of the Baltic region experienced an unprecedented deterioration in life expectancy. In Estonia, life expectancy at birth fell by 4 years from 1988 to 1994. Subsequently, there has been an upturn in life expectancy, although in 1996 life expectancy at birth in Estonia was still lower than in 1988.1 Information on social variation in the health of people in Central and Eastern Europe is limited. The available data suggest that considerable differences do exist and that the process of economic and political transition tends to lead to an increase in health inequality within countries.2,3 The existence of comprehensive birth registration in Estonia since 1992, which involves routine collection of socio-demographic data, presents a unique opportunity to study birth outcome, and its social variation, during the period of transition in this former Soviet country. In Estonia, the possibility of independence from the USSR became tangible as early as 1988. Shortly after the coup attempt against Gorbachev in Moscow in August 1991, Estonia declared full independence. A series of major political and economic reforms followed, affecting practically all aspects of people's lives. The economic situation was already deteriorating in Estonia in 1990 and 1991. However, 1992 saw the most dramatic decline in gross domestic product (GDP) (by 14%) and in the gross industrial product (by 39%). In terms of GDP growth, the economic situation then gradually improved in the following years. Compared to the year 1989, real wages were only 45% in 1992 and despite the subsequent improvements they only reached 55% of the baseline level in 1997.4 The aim of the present study is to investigate the effect of maternal social characteristics, such as education, marital status or nationality, on birthweight and the frequency of preterm birth in Estonia during 6 years of major societal change and reform. Material and Methods The Estonian Medical Birth Registry was established in 1991. Since 1992, it has collected, among other health indicators, data on year of birth, child's sex, single/multiple birth, weight and length at birth, gestational age, mother's parity, age, marital status, education, nationality and smoking habits. Data on live- and stillbirths are gathered from all hospitals providing obstetric services in Estonia. The WHO definition of live birth5 has been used in Estonia since 1 January 1992. Birthweight is usually rounded to the nearest 10 g, less often to the nearest 50 or 100 g. Birth length is rounded to the nearest one cm. Information on gestational age is based on date of last menstrual period and/or ultrasound examination. In our analyses, maternal education was classified in four categories: basic or less, secondary, higher (secondary special or vocational) and university. Mother's marital status was classified as married, cohabiting and other (single, divorced or widowed). Categories of mother's nationality were Estonian and other. Data on smoking status was collected and analysed in three categories: ‘did not smoke during pregnancy’, ‘quit smoking during the first trimester’, and ‘continued to smoke during pregnancy’. We used 5-year age categories (<20, 20-, 25-, ... 40+) and six categories of parity (0, 1, ... 5+ previous liveand stillbirths). Preterm birth refers to a birth that occurs at a gestational age of <37 completed weeks.6 In multivariate analyses, adjustments for gestational age were made with gestational age in completed weeks as a factor. There were 84 629 live births resulting from singleton pregnancies reported to the Estonian Medical Birth Registry in 1992–1997. For 84 604 (>99.9%) of the singleton live births, data on birthweight were available. Information on either length at birth, gestational age, sex of the newborn, maternal age, parity or one or more of the social characteristics was missing in 1.0% of births. In another 2.3% births, data on maternal smoking habits were missing. In total, 2830 (3.3%) of all singleton live births were excluded from multivariate analyses because of missing data for one or more of the variables studied. Those excluded from the multivariate analyses tended to be of lower than average birthweight (3380 g versus 3485 g, P < 0.001), were more likely to be born preterm (9.4% versus 5.2%, P < 0.001) and were more likely to be born to mothers with lower education or those not married. Linear and logistic regression were used to quantify the effect of maternal characteristics on size at birth and risk of preterm birth, with and without adjustments for potential confounders. Data management was performed in FoxPro 2.6; analyses were carried out using the STATA statistical package.7 The use of the data from the Medical Birth Registry was in accordance with its statutory obligations to protect confidentiality. Results Demographic characteristics of the sample The age of mothers ranged from 13 to 50 years, with a mean age of 25.1 years (SD 5.5). The proportion of boys among the live births was 51.5%. Of mothers, 73% were of Estonian nationality, 22% were Russians, 2% Ukrainians, 1% Belorussians, and 2% were of other nationality. At the time of delivery, 58% of mothers were married, 34% were cohabiting, 7% were single and less than 1% were divorced or widowed. With increasing level of education, mothers were more likely to be married and less likely to be cohabiting or single. The proportion of nulliparous mothers was lowest among the university educated (43%) and highest among those with basic or lower education (55%). The proportion of women who smoked at some stage of pregnancy decreased with educational level (Table 1). The proportion of women with basic or lower education was higher in Estonian mothers (16%) than in non-Estonians (10%), while the proportion of university-educated women was similar in these two groups (13% and 12%, respectively). Women of non-Estonian nationality were more likely to be married than the Estonians (72% versus 53%) and less likely to be cohabiting (20% versus 39%). Nationality was only weakly related to smoking habits, the non-Estonians being slightly more likely to continue to smoke during pregnancy. Distribution of birthweight and proportion of preterm births Birthweight showed a distribution that was slightly skewed to the left, with a mean of 3482 g. The mean length at birth was 50.7 cm. The preterm rate was 5.3% (Table 1). Boys were on average heavier at birth (3550 g versus 3409 g, P < 0.001) and were only slightly more often born preterm than girls (5.4% versus 5.2%, P = 0.221). Mean birthweight by maternal age and parity is shown in Table 1. Variation in birthweight and preterm births by social characteristics Maternal education, marital status and nationality were all independently related to birthweight of the offspring. These effects were only partly explained by maternal age, parity and sex of the infant and persisted after additional adjustments for gestational age. Adjustments for maternal smoking further reduced the difference in mean birthweight between the respective social categories, although it remained substantial and statistically significant (Table 2). The effect of adjustment for potential confounders differed according to the socio-demographic variables. For instance, a substantial part of the effect of marital status, but not of education or nationality, was explained by adjustment for maternal age, parity and sex of the infant. The additional adjustments for gestational age and maternal smoking then reduced the effect of marital status to a third, halved the effect of maternal education, but explained only a small part of the effect of mother's nationality (Table 2). The lowest mean birthweight was found in children of mothers with lowest education, mothers of non-Estonian nationality and those not married or cohabiting. Children of mothers with basic or lower education, of mothers who were not married or cohabiting and mothers with other than Estonian nationality were also at the highest risk of being born preterm. The effect of maternal social characteristics on frequency of preterm birth was only partially explained by maternal age, parity, smoking habits or sex of the infant (Table 3). Trends between 1992 and 1997 Substantial demographic changes occurring in Estonia over the study period are reflected in our data. The substantial decline in birth rates is seen in the numbers of births over the period of our study (Table 4). The mean age of mothers increased slightly, from 25.0 years in 1992 to 25.7 years in 1997 (both SD 5.6 years, P < 0.001). The proportion of teenage mothers (<20 years) decreased from 15% in 1992 and 1993 to 12% in 1997. No appreciable changes were seen in parity. The most dramatic change concerns the proportion of infants born outside marriage. In 1992, only 27% of live-born singletons were born to cohabiting mothers and 7% were born to single, divorced or widowed mothers; these proportions rose to 41% and 10%, respectively, in 1997. The proportion of mothers with basic or lower education increased over the study period. There were only minor changes in the nationality structure of the maternal population (Table 4). Over the study period smoking became more common: the proportion of women who smoked at some stage of pregnancy doubled between 1992 and 1997 (Table 4). Between 1992 and 1997, mean birthweight increased from 3465 g to 3497 g (P < 0.001) and the proportion of preterm births fell from 5.8% to 5.1% (P = 0.001). The trends in mean birthweight by maternal education, marital status and nationality are shown in Figure 1. The increasing differences in mean birthweight between children of mothers with basic compared to university education between 1992 and 1997 were only partly explained by changes in the age, parity, marital status or nationality structure of the populations, changing smoking habits or gestational age. The adjusted mean difference in birthweight between children of mothers with basic compared to university education more than doubled between 1992 and 1997 (Table 5). On the other hand, the effect of maternal marital status on the mean birthweight increased only slightly after 1992, the gap between single and other groups widening in particular. The effect of mother's nationality on birthweight of the offspring was also strongest in 1997 but time trends were not consistent (Table 5). There was no evidence of an interaction between nationality and other social characteristics in their effect on birthweight (not shown). There was no systematic change in the strength of the effect of maternal social characteristics on preterm births over the study period other than an increasing difference between married and single mothers. The odds ratio for a preterm birth in single compared to married mothers was 1.31 (95% CI : 1.02–1.68) in 1992 and 1.51 (95% CI : 1.15–1.98) in 1997, adjusted for maternal age, parity, education, nationality, smoking and sex of the infant. Discussion Our analyses of data on singleton live births in Estonia in 1992– 1997 show that the mean birthweight increased and preterm rate decreased during this period but the improvements were not shared equally by all social groups in the country. Validity The validity of the time-trend analysis depends on the completeness and comparability of the data. The data were collected by a routine registration system that had been in operation since 1992. No systematic investigations of the quality of data have been undertaken, however, we are not aware of any administrative or other changes that would compromise the quality or completeness of the data during the study period. Consistency checks such as exploring the relations between birthweight, length at birth and length of gestation did not reveal any appreciable inconsistencies. The proportion of births with missing data on birth outcome indices or maternal characteristics was small and stable (2.8–3.6%) during the study period and could not substantially affect the validity of the time-trend comparisons. The data on smoking do not provide a good quantitative estimate of the number of cigarettes smoked before conception and at different stages of pregnancy,8 and we thus cannot exclude a possibility of some residual confounding by this powerful determinant of birth outcome in our study. Birthweight and preterm rate in Estonia compared to other countries The proportion of preterm births in Estonia (5.3%) is similar to that in Sweden in 1989–1991 (5.4%).9 The overall mean birthweight of 3482 g is considerably higher that the mean birthweight in the Czech Republic in 1996 (3353 g),3 and only slightly lower than in Sweden in 1989–1991 (3522 g).9 This pattern is consistent with previous international comparisons of birth outcomes that repeatedly reported high birthweight in Nordic countries.10,11 Due to the lack of comparable data on anthropometric characteristics of the Estonian population, it is not practicable to quantify the potential contribution of parental height and weight to the differences in size at birth. Only a small part of the differences in overall mean birthweight between the three populations can be explained by maternal age or parity as the differences are present in all maternal age and parity strata. Social variation in birthweight and preterm rate We found considerable variation in mean birthweight by maternal education, marital status and nationality. Children born to mothers with lower education, not married or cohabiting and those with non-Estonian nationality were on average lighter. Only part of this variation could be explained by maternal age, parity, smoking and by sex and gestational age of the infant. The pattern in which maternal education was related to birthweight of the offspring was remarkably similar to that in the Czech population,3,9 the difference between women with basic or lower education and the other educational groups being particularly pronounced. The size of the effect of maternal education was greater in Estonia than in Sweden and very similar to the effects seen in the Czech Republic. On the other hand, the effect of maternal marital status was smaller and the effect of nationality greater in Estonia than in the other two populations. Lower maternal education, not married/not cohabiting status and non-Estonian nationality were also independently related to a higher risk of preterm birth. The effect of maternal education was particularly strong and persisted after adjustments for maternal age, parity, smoking and sex of the infant. Overall, the extent of social variation in frequency of preterm birth in Estonia was greater than in Sweden and only slightly less pronounced than in the Czech Republic in 1989–1991.9 There were substantial differences in mean birthweight and proportion of preterm births between Estonian and non-Estonian nationals, the majority of whom are of Russian origin. The findings on differences in mean birthweight and preterm births between Estonians and non-Estonians resident in Estonia are consistent with a study on determinants of perinatal mortality in Estonia.8 Very little of the effect of nationality on birth outcome could be explained by factors such as maternal age, parity, sex or gestational age of the infant, or mother's smoking habits, although a higher prevalence of smoking has been recently shown in non-Estonians compared to Estonians.12 In our study, the association of nationality with smoking in pregnancy was weak and it is possible that some of the effect of nationality seen in our data may be due to a residual confounding by smoking. It is also conceivable that other characteristics such as height or weight of the mothers could contribute to the variation in size at birth by nationality. It may also be that non-Estonian nationals resident in Estonia are socially or economically disadvantaged in a way that is not adequately captured by their education and marital status. For example, unemployment is higher among non-Estonians,13 and it is possible that higher risk of unemployment contributes to differences in behaviour, socioeconomic circumstances or generally increases the level of stress. Trends The transformation process in Estonia has led to a deep economic depression and a concomitant decline in people's welfare. The national economy bottomed out in 1992 and subsequently started to show signs of socioeconomic and political stabilization. After the sudden failure of the social security system and a rise in social deprivation in the early 1990s, Estonia has been experiencing an upswing in the national economy and people's welfare and well-being has been increasing in more recent years. However, significant economic and social disparities exist; the poorest groups being dominated by ethnic minorities, pensioners, the unemployed and single parents.14 Economic inequalities have substantially increased in recent years and a link between education and income is becoming more pronounced.15 A substantial decline in fertility rates is reflected in the numbers of births over the period of our study.16 At least until 1993, declining birth rates affected Estonians and other nationalities resident in Estonia to a similar degree.17 Little is known about the changes in fertility patterns by maternal education and other social characteristics. One of the most dramatic recent demographic trends in Estonia has been the gradually increasing proportion of births to unmarried, cohabiting mothers. It is thus surprising to see that the difference in birthweight or preterm births between married and cohabiting mothers was not disappearing, but indeed, slightly increased over the study period. This trend is very different from a situation in e.g. Sweden, where the proportion of births outside marriage is also high but the difference in birth outcome between married and non-married cohabiting women is very small.18 The apparent increase in variation in mean birthweight by maternal education is consistent with our findings of increasing social variation in birth outcome during the transition in the Czech Republic.3 It is plausible that the divergence in birth outcome between socioeconomic groups is related to the divergence in living standards, as the economic benefits of education are becoming increasingly important in the transition countries.4 This is consistent with the literature showing that birthweight is sensitive to socioeconomic factors in other populations.19–21 Finally, it is important to note that the generally favourable trends in birth outcome in Estonia from 1992 to 1997 are not consistent with trends in life expectancy or adult mortality.22 While adult mortality dramatically increased between 1992 and 1994, we noted a marked improvement in birth outcome over the same period. This could mean that the main effects of transition on birth outcome occurred through changes in fertility or that the transition was indeed affecting various age groups in very different ways. Conclusions During the period 1992–1997, Estonia experienced an overall increase in mean birthweight and a decrease in proportion of preterm births. At the same time, social variation in birth outcomes was increasing in Estonia, as the group with lowest education failed to benefit from the changes brought about by the transition. There were also considerable differences in mean birthweight and proportion of preterm births between Estonians and non-Estonians resident in Estonia, although these differences did not show any tendency to widen during the period of study. Table 1 Maternal smoking and mean birthweight (g), length (cm) at birth, proportion of preterm deliveries (<37 weeks gestation) in singleton live born infants in Estonia, 1992–1997, by maternal age, parity and social characteristics . n . Birthweight . Length . Preterm . Smoking in pregnancy . Because of missing values, birth length was available for only 84 557, preterm status for 84 555 and smoking status for 82 654. Maternal age (years) <20 11 799 3369 50.3 6.7% 8.8% 20–24 32 666 3466 50.7 4.7% 6.1% 25–29 22 326 3536 50.9 4.2% 5.8% 30–34 11 661 3531 50.8 6.1% 6.5% 35–39 4975 3502 50.7 7.4% 8.6% 40+ 1111 3433 50.4 10.6% 11.4% Not known 66 3491 50.8 10.9% 11.1% Parity 0 42 192 3413 50.5 5.1% 6.2% 1 26 496 3552 50.9 4.6% 5.7% 2 9760 3559 50.9 5.9% 8.0% 3 3361 3543 50.8 7.6% 10.8% 4 1443 3509 50.8 8.7% 13.0% 5+ 1352 3513 50.7 9.5% 13.8% Mother's education Basic or less 12 048 3364 50.2 7.8% 16.3% Secondary 33 253 3479 50.7 5.2% 6.6% Higher 28 105 3510 50.9 4.8% 4.5% University 10 734 3553 50.8 3.9% 1.7% Not known 464 3402 50.5 8.3% 7.1% Mother's marital status Married 49 321 3517 50.8 4.6% 4.0% Cohabiting 28 493 3448 50.6 6.0% 9.4% Other 6642 3367 50.3 7.3% 15.0% Not known 148 3337 50.2 11.1% 8.6% Mother's nationality Estonian 61 250 3512 50.8 5.1% 6.2% Other 23 217 3404 50.5 5.7% 8.0% Not known 137 3378 50.7 7.5% 6.8% Total 84 604 3482 50.7 5.3% 6.7% (SD) (545) (2.7) . n . Birthweight . Length . Preterm . Smoking in pregnancy . Because of missing values, birth length was available for only 84 557, preterm status for 84 555 and smoking status for 82 654. Maternal age (years) <20 11 799 3369 50.3 6.7% 8.8% 20–24 32 666 3466 50.7 4.7% 6.1% 25–29 22 326 3536 50.9 4.2% 5.8% 30–34 11 661 3531 50.8 6.1% 6.5% 35–39 4975 3502 50.7 7.4% 8.6% 40+ 1111 3433 50.4 10.6% 11.4% Not known 66 3491 50.8 10.9% 11.1% Parity 0 42 192 3413 50.5 5.1% 6.2% 1 26 496 3552 50.9 4.6% 5.7% 2 9760 3559 50.9 5.9% 8.0% 3 3361 3543 50.8 7.6% 10.8% 4 1443 3509 50.8 8.7% 13.0% 5+ 1352 3513 50.7 9.5% 13.8% Mother's education Basic or less 12 048 3364 50.2 7.8% 16.3% Secondary 33 253 3479 50.7 5.2% 6.6% Higher 28 105 3510 50.9 4.8% 4.5% University 10 734 3553 50.8 3.9% 1.7% Not known 464 3402 50.5 8.3% 7.1% Mother's marital status Married 49 321 3517 50.8 4.6% 4.0% Cohabiting 28 493 3448 50.6 6.0% 9.4% Other 6642 3367 50.3 7.3% 15.0% Not known 148 3337 50.2 11.1% 8.6% Mother's nationality Estonian 61 250 3512 50.8 5.1% 6.2% Other 23 217 3404 50.5 5.7% 8.0% Not known 137 3378 50.7 7.5% 6.8% Total 84 604 3482 50.7 5.3% 6.7% (SD) (545) (2.7) Open in new tab Table 1 Maternal smoking and mean birthweight (g), length (cm) at birth, proportion of preterm deliveries (<37 weeks gestation) in singleton live born infants in Estonia, 1992–1997, by maternal age, parity and social characteristics . n . Birthweight . Length . Preterm . Smoking in pregnancy . Because of missing values, birth length was available for only 84 557, preterm status for 84 555 and smoking status for 82 654. Maternal age (years) <20 11 799 3369 50.3 6.7% 8.8% 20–24 32 666 3466 50.7 4.7% 6.1% 25–29 22 326 3536 50.9 4.2% 5.8% 30–34 11 661 3531 50.8 6.1% 6.5% 35–39 4975 3502 50.7 7.4% 8.6% 40+ 1111 3433 50.4 10.6% 11.4% Not known 66 3491 50.8 10.9% 11.1% Parity 0 42 192 3413 50.5 5.1% 6.2% 1 26 496 3552 50.9 4.6% 5.7% 2 9760 3559 50.9 5.9% 8.0% 3 3361 3543 50.8 7.6% 10.8% 4 1443 3509 50.8 8.7% 13.0% 5+ 1352 3513 50.7 9.5% 13.8% Mother's education Basic or less 12 048 3364 50.2 7.8% 16.3% Secondary 33 253 3479 50.7 5.2% 6.6% Higher 28 105 3510 50.9 4.8% 4.5% University 10 734 3553 50.8 3.9% 1.7% Not known 464 3402 50.5 8.3% 7.1% Mother's marital status Married 49 321 3517 50.8 4.6% 4.0% Cohabiting 28 493 3448 50.6 6.0% 9.4% Other 6642 3367 50.3 7.3% 15.0% Not known 148 3337 50.2 11.1% 8.6% Mother's nationality Estonian 61 250 3512 50.8 5.1% 6.2% Other 23 217 3404 50.5 5.7% 8.0% Not known 137 3378 50.7 7.5% 6.8% Total 84 604 3482 50.7 5.3% 6.7% (SD) (545) (2.7) . n . Birthweight . Length . Preterm . Smoking in pregnancy . Because of missing values, birth length was available for only 84 557, preterm status for 84 555 and smoking status for 82 654. Maternal age (years) <20 11 799 3369 50.3 6.7% 8.8% 20–24 32 666 3466 50.7 4.7% 6.1% 25–29 22 326 3536 50.9 4.2% 5.8% 30–34 11 661 3531 50.8 6.1% 6.5% 35–39 4975 3502 50.7 7.4% 8.6% 40+ 1111 3433 50.4 10.6% 11.4% Not known 66 3491 50.8 10.9% 11.1% Parity 0 42 192 3413 50.5 5.1% 6.2% 1 26 496 3552 50.9 4.6% 5.7% 2 9760 3559 50.9 5.9% 8.0% 3 3361 3543 50.8 7.6% 10.8% 4 1443 3509 50.8 8.7% 13.0% 5+ 1352 3513 50.7 9.5% 13.8% Mother's education Basic or less 12 048 3364 50.2 7.8% 16.3% Secondary 33 253 3479 50.7 5.2% 6.6% Higher 28 105 3510 50.9 4.8% 4.5% University 10 734 3553 50.8 3.9% 1.7% Not known 464 3402 50.5 8.3% 7.1% Mother's marital status Married 49 321 3517 50.8 4.6% 4.0% Cohabiting 28 493 3448 50.6 6.0% 9.4% Other 6642 3367 50.3 7.3% 15.0% Not known 148 3337 50.2 11.1% 8.6% Mother's nationality Estonian 61 250 3512 50.8 5.1% 6.2% Other 23 217 3404 50.5 5.7% 8.0% Not known 137 3378 50.7 7.5% 6.8% Total 84 604 3482 50.7 5.3% 6.7% (SD) (545) (2.7) Open in new tab Table 2 The effect of maternal education, marital status and nationality on birthweight (g) of the offspring. Estonia, 1992–1997 (singleton live births only) . . . Adjusted for: . . n . Crude β (95% CI) . Sex, age, parity β (95% CI) . + other social variablesa β (95% CI) . + gest. age β (95% CI) . + smoking β (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 –185 (–199, –171) –170 (–186, –154) –150 (–166, –134) –107 (–120, –94) –87 (–100, –74) Secondary 32 265 –73 (–85, –61) –66 (–78, –53) –50 (–63, –38) –38 (–48, –28) –32 (–41, –22) Higher 27 438 –43 (–55, –31) –43 (–56, –31) –33 (–45, –21) –25 (–35, –15) –22 (–31, –12) Universityb 10 513 0 0 0 0 0 P-value trend (1 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 0 0 0 0 0 Cohabiting 27 564 –69 (–77, –61) –44 (–52, –36) –48 (–57, –40) –27 (–34, –20) –20 (–27, –14) Other 6311 –146 (–160, –132) –97 (–111, –83) –87 (–101, –72) –52 (–63, –40) –37 (–49, –26) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 0 0 0 0 0 Other 22 433 –107 (–115, –98) –90 (–98, –81) –105 (–114, –97) –83 (–90, –76) –77 (–84, –71) P-value <0.001 <0.001 <0.001 <0.001 <0.001 . . . Adjusted for: . . n . Crude β (95% CI) . Sex, age, parity β (95% CI) . + other social variablesa β (95% CI) . + gest. age β (95% CI) . + smoking β (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 –185 (–199, –171) –170 (–186, –154) –150 (–166, –134) –107 (–120, –94) –87 (–100, –74) Secondary 32 265 –73 (–85, –61) –66 (–78, –53) –50 (–63, –38) –38 (–48, –28) –32 (–41, –22) Higher 27 438 –43 (–55, –31) –43 (–56, –31) –33 (–45, –21) –25 (–35, –15) –22 (–31, –12) Universityb 10 513 0 0 0 0 0 P-value trend (1 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 0 0 0 0 0 Cohabiting 27 564 –69 (–77, –61) –44 (–52, –36) –48 (–57, –40) –27 (–34, –20) –20 (–27, –14) Other 6311 –146 (–160, –132) –97 (–111, –83) –87 (–101, –72) –52 (–63, –40) –37 (–49, –26) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 0 0 0 0 0 Other 22 433 –107 (–115, –98) –90 (–98, –81) –105 (–114, –97) –83 (–90, –76) –77 (–84, –71) P-value <0.001 <0.001 <0.001 <0.001 <0.001 Open in new tab Table 2 The effect of maternal education, marital status and nationality on birthweight (g) of the offspring. Estonia, 1992–1997 (singleton live births only) . . . Adjusted for: . . n . Crude β (95% CI) . Sex, age, parity β (95% CI) . + other social variablesa β (95% CI) . + gest. age β (95% CI) . + smoking β (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 –185 (–199, –171) –170 (–186, –154) –150 (–166, –134) –107 (–120, –94) –87 (–100, –74) Secondary 32 265 –73 (–85, –61) –66 (–78, –53) –50 (–63, –38) –38 (–48, –28) –32 (–41, –22) Higher 27 438 –43 (–55, –31) –43 (–56, –31) –33 (–45, –21) –25 (–35, –15) –22 (–31, –12) Universityb 10 513 0 0 0 0 0 P-value trend (1 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 0 0 0 0 0 Cohabiting 27 564 –69 (–77, –61) –44 (–52, –36) –48 (–57, –40) –27 (–34, –20) –20 (–27, –14) Other 6311 –146 (–160, –132) –97 (–111, –83) –87 (–101, –72) –52 (–63, –40) –37 (–49, –26) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 0 0 0 0 0 Other 22 433 –107 (–115, –98) –90 (–98, –81) –105 (–114, –97) –83 (–90, –76) –77 (–84, –71) P-value <0.001 <0.001 <0.001 <0.001 <0.001 . . . Adjusted for: . . n . Crude β (95% CI) . Sex, age, parity β (95% CI) . + other social variablesa β (95% CI) . + gest. age β (95% CI) . + smoking β (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 –185 (–199, –171) –170 (–186, –154) –150 (–166, –134) –107 (–120, –94) –87 (–100, –74) Secondary 32 265 –73 (–85, –61) –66 (–78, –53) –50 (–63, –38) –38 (–48, –28) –32 (–41, –22) Higher 27 438 –43 (–55, –31) –43 (–56, –31) –33 (–45, –21) –25 (–35, –15) –22 (–31, –12) Universityb 10 513 0 0 0 0 0 P-value trend (1 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 0 0 0 0 0 Cohabiting 27 564 –69 (–77, –61) –44 (–52, –36) –48 (–57, –40) –27 (–34, –20) –20 (–27, –14) Other 6311 –146 (–160, –132) –97 (–111, –83) –87 (–101, –72) –52 (–63, –40) –37 (–49, –26) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 0 0 0 0 0 Other 22 433 –107 (–115, –98) –90 (–98, –81) –105 (–114, –97) –83 (–90, –76) –77 (–84, –71) P-value <0.001 <0.001 <0.001 <0.001 <0.001 Open in new tab Table 3 Odds ratios for a preterm birth (<37 weeks gestation) with 95% CI, by maternal education, marital status and nationality in Estonia, 1992–1997 (singleton live births only) . . . Adjusted for: . . n . Crude OR (95% CI) . Sex, age, parity OR (95% CI) . + other social variablesa OR (95% CI) . + smoking OR (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 2.04 (1.81, 2.31) 1.98 (1.72, 2.27) 1.75 (1.52, 2.01) 1.62 (1.40, 1.86) Secondary 32 265 1.37 (1.22, 1.53) 1.42 (1.26, 1.59) 1.33 (1.18, 1.50) 1.30 (1.15, 1.46) Higher 27 438 1.26 (1.12, 1.41) 1.32 (1.18, 1.49) 1.27 (1.13, 1.43) 1.25 (1.11, 1.41) Universityb 10 513 1.0 1.0 1.0 1.0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 1.0 1.0 1.0 1.0 Cohabiting 27 564 1.34 (1.25, 1.43) 1.33 (1.24, 1.42) 1.30 (1.21, 1.40) 1.26 (1.18, 1.35) Other 6311 1.59 (1.43, 1.77) 1.57 (1.40, 1.75) 1.48 (1.32, 1.66) 1.39 (1.25, 1.56) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 1.0 1.0 1.0 1.0 Other 22 433 1.10 (1.03, 1.18) 1.11 (1.04, 1.19) 1.20 (1.12, 1.29) 1.17 (1.09, 1.25) P-value 0.006 0.002 <0.001 <0.001 . . . Adjusted for: . . n . Crude OR (95% CI) . Sex, age, parity OR (95% CI) . + other social variablesa OR (95% CI) . + smoking OR (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 2.04 (1.81, 2.31) 1.98 (1.72, 2.27) 1.75 (1.52, 2.01) 1.62 (1.40, 1.86) Secondary 32 265 1.37 (1.22, 1.53) 1.42 (1.26, 1.59) 1.33 (1.18, 1.50) 1.30 (1.15, 1.46) Higher 27 438 1.26 (1.12, 1.41) 1.32 (1.18, 1.49) 1.27 (1.13, 1.43) 1.25 (1.11, 1.41) Universityb 10 513 1.0 1.0 1.0 1.0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 1.0 1.0 1.0 1.0 Cohabiting 27 564 1.34 (1.25, 1.43) 1.33 (1.24, 1.42) 1.30 (1.21, 1.40) 1.26 (1.18, 1.35) Other 6311 1.59 (1.43, 1.77) 1.57 (1.40, 1.75) 1.48 (1.32, 1.66) 1.39 (1.25, 1.56) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 1.0 1.0 1.0 1.0 Other 22 433 1.10 (1.03, 1.18) 1.11 (1.04, 1.19) 1.20 (1.12, 1.29) 1.17 (1.09, 1.25) P-value 0.006 0.002 <0.001 <0.001 Open in new tab Table 3 Odds ratios for a preterm birth (<37 weeks gestation) with 95% CI, by maternal education, marital status and nationality in Estonia, 1992–1997 (singleton live births only) . . . Adjusted for: . . n . Crude OR (95% CI) . Sex, age, parity OR (95% CI) . + other social variablesa OR (95% CI) . + smoking OR (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 2.04 (1.81, 2.31) 1.98 (1.72, 2.27) 1.75 (1.52, 2.01) 1.62 (1.40, 1.86) Secondary 32 265 1.37 (1.22, 1.53) 1.42 (1.26, 1.59) 1.33 (1.18, 1.50) 1.30 (1.15, 1.46) Higher 27 438 1.26 (1.12, 1.41) 1.32 (1.18, 1.49) 1.27 (1.13, 1.43) 1.25 (1.11, 1.41) Universityb 10 513 1.0 1.0 1.0 1.0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 1.0 1.0 1.0 1.0 Cohabiting 27 564 1.34 (1.25, 1.43) 1.33 (1.24, 1.42) 1.30 (1.21, 1.40) 1.26 (1.18, 1.35) Other 6311 1.59 (1.43, 1.77) 1.57 (1.40, 1.75) 1.48 (1.32, 1.66) 1.39 (1.25, 1.56) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 1.0 1.0 1.0 1.0 Other 22 433 1.10 (1.03, 1.18) 1.11 (1.04, 1.19) 1.20 (1.12, 1.29) 1.17 (1.09, 1.25) P-value 0.006 0.002 <0.001 <0.001 . . . Adjusted for: . . n . Crude OR (95% CI) . Sex, age, parity OR (95% CI) . + other social variablesa OR (95% CI) . + smoking OR (95% CI) . a Adjusted for the other two social variables in the Table. b Baseline category. Mother's education Basic or less 11 583 2.04 (1.81, 2.31) 1.98 (1.72, 2.27) 1.75 (1.52, 2.01) 1.62 (1.40, 1.86) Secondary 32 265 1.37 (1.22, 1.53) 1.42 (1.26, 1.59) 1.33 (1.18, 1.50) 1.30 (1.15, 1.46) Higher 27 438 1.26 (1.12, 1.41) 1.32 (1.18, 1.49) 1.27 (1.13, 1.43) 1.25 (1.11, 1.41) Universityb 10 513 1.0 1.0 1.0 1.0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 47 924 1.0 1.0 1.0 1.0 Cohabiting 27 564 1.34 (1.25, 1.43) 1.33 (1.24, 1.42) 1.30 (1.21, 1.40) 1.26 (1.18, 1.35) Other 6311 1.59 (1.43, 1.77) 1.57 (1.40, 1.75) 1.48 (1.32, 1.66) 1.39 (1.25, 1.56) P-value heterog. (2 d.f.) <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 59 366 1.0 1.0 1.0 1.0 Other 22 433 1.10 (1.03, 1.18) 1.11 (1.04, 1.19) 1.20 (1.12, 1.29) 1.17 (1.09, 1.25) P-value 0.006 0.002 <0.001 <0.001 Open in new tab Table 4 Distribution (%) of education, marital status, nationality and smoking status in pregnancy among mothers of singleton live-born infants in Estonia, 1992–1997 . 1992 (n = 17 068) . 1993 (n = 14 367) . 1994 (n = 13 282) . 1995 (n = 12 693) . 1996 (n = 12 450) . 1997 (n = 11 939) . Mother's education Basic or less 11.2 12.7 14.5 15.3 16.1 16.5 Secondary 41.2 42.1 39.6 38.0 37.5 37.1 Higher 34.2 31.7 34.0 34.2 34.1 33.2 University 13.4 13.5 11.9 12.5 12.3 13.2 Mother's marital status Married 66.8 62.5 60.0 56.4 52.7 49.1 Cohabiting 26.7 30.9 33.0 35.2 38.5 41.3 Other 6.5 6.6 7.0 8.4 8.8 9.6 Mother's nationality Estonian 70.6 73.9 73.5 72.7 72.7 72.5 Other 29.4 26.1 26.4 27.3 27.3 27.5 Smoking in pregnancy % smokers 5.4% 4.7% 5.5% 6.6% 8.0% 10.8% . 1992 (n = 17 068) . 1993 (n = 14 367) . 1994 (n = 13 282) . 1995 (n = 12 693) . 1996 (n = 12 450) . 1997 (n = 11 939) . Mother's education Basic or less 11.2 12.7 14.5 15.3 16.1 16.5 Secondary 41.2 42.1 39.6 38.0 37.5 37.1 Higher 34.2 31.7 34.0 34.2 34.1 33.2 University 13.4 13.5 11.9 12.5 12.3 13.2 Mother's marital status Married 66.8 62.5 60.0 56.4 52.7 49.1 Cohabiting 26.7 30.9 33.0 35.2 38.5 41.3 Other 6.5 6.6 7.0 8.4 8.8 9.6 Mother's nationality Estonian 70.6 73.9 73.5 72.7 72.7 72.5 Other 29.4 26.1 26.4 27.3 27.3 27.5 Smoking in pregnancy % smokers 5.4% 4.7% 5.5% 6.6% 8.0% 10.8% Open in new tab Table 4 Distribution (%) of education, marital status, nationality and smoking status in pregnancy among mothers of singleton live-born infants in Estonia, 1992–1997 . 1992 (n = 17 068) . 1993 (n = 14 367) . 1994 (n = 13 282) . 1995 (n = 12 693) . 1996 (n = 12 450) . 1997 (n = 11 939) . Mother's education Basic or less 11.2 12.7 14.5 15.3 16.1 16.5 Secondary 41.2 42.1 39.6 38.0 37.5 37.1 Higher 34.2 31.7 34.0 34.2 34.1 33.2 University 13.4 13.5 11.9 12.5 12.3 13.2 Mother's marital status Married 66.8 62.5 60.0 56.4 52.7 49.1 Cohabiting 26.7 30.9 33.0 35.2 38.5 41.3 Other 6.5 6.6 7.0 8.4 8.8 9.6 Mother's nationality Estonian 70.6 73.9 73.5 72.7 72.7 72.5 Other 29.4 26.1 26.4 27.3 27.3 27.5 Smoking in pregnancy % smokers 5.4% 4.7% 5.5% 6.6% 8.0% 10.8% . 1992 (n = 17 068) . 1993 (n = 14 367) . 1994 (n = 13 282) . 1995 (n = 12 693) . 1996 (n = 12 450) . 1997 (n = 11 939) . Mother's education Basic or less 11.2 12.7 14.5 15.3 16.1 16.5 Secondary 41.2 42.1 39.6 38.0 37.5 37.1 Higher 34.2 31.7 34.0 34.2 34.1 33.2 University 13.4 13.5 11.9 12.5 12.3 13.2 Mother's marital status Married 66.8 62.5 60.0 56.4 52.7 49.1 Cohabiting 26.7 30.9 33.0 35.2 38.5 41.3 Other 6.5 6.6 7.0 8.4 8.8 9.6 Mother's nationality Estonian 70.6 73.9 73.5 72.7 72.7 72.5 Other 29.4 26.1 26.4 27.3 27.3 27.5 Smoking in pregnancy % smokers 5.4% 4.7% 5.5% 6.6% 8.0% 10.8% Open in new tab Table 5 The effect of maternal education, marital status and nationality on birthweight (g) of offspring by year: Estonia, 1992–1997 (singleton live births only) . 1992 β (95% CI)a . 1993 β (95% CI)a . 1994 β (95% CI)a . 1995 β (95% CI)a . 1996 β (95% CI)a . 1997 β (95% CI)a . a All regression coefficients are adjusted for the other two social variables in the Table, maternal age, parity, smoking, gestational age and sex of the infant. b Baseline category. Mother's education Basic or less –50 (–80, –21) –95 (–126, –64) –89 (–121, –56) –90 (–122, –58) –95 (–128, –62) –121 (–154, –87) Secondary –27 (–49, –6) –27 (–50, –4) –36 (–62, –11) –31 (–56, –6) –27 (–53, –1) –45 (–71, –19) Higher –18 (–40, 3) –14 (–38, 9) –28 (–53, –3) –24 (–49, 0) –16 (–42, 9) –32 (–58, –7) Universityb 0 0 0 0 0 0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 0 0 0 0 0 0 Cohabiting –16 (–31, 0) –13 (–29, 3) –32 (–49, –16) –27 (–43, –10) –26 (–43, –9) –26 (–43, –9) Other –13 (–40, 14) –50 (–79, –21) –40 (–70, –11) –49 (–77, –21) –49 (–77, –21) –39 (–67, –11) P-value heterog. (2 d.f.) 0.123 0.002 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 0 0 0 0 0 0 Other –77 (–92, –63) –72 (–88, –55) –75 (–92, –58) –67 (–83, –50) –80 (–98, –63) –94 (–112, –77) P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 . 1992 β (95% CI)a . 1993 β (95% CI)a . 1994 β (95% CI)a . 1995 β (95% CI)a . 1996 β (95% CI)a . 1997 β (95% CI)a . a All regression coefficients are adjusted for the other two social variables in the Table, maternal age, parity, smoking, gestational age and sex of the infant. b Baseline category. Mother's education Basic or less –50 (–80, –21) –95 (–126, –64) –89 (–121, –56) –90 (–122, –58) –95 (–128, –62) –121 (–154, –87) Secondary –27 (–49, –6) –27 (–50, –4) –36 (–62, –11) –31 (–56, –6) –27 (–53, –1) –45 (–71, –19) Higher –18 (–40, 3) –14 (–38, 9) –28 (–53, –3) –24 (–49, 0) –16 (–42, 9) –32 (–58, –7) Universityb 0 0 0 0 0 0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 0 0 0 0 0 0 Cohabiting –16 (–31, 0) –13 (–29, 3) –32 (–49, –16) –27 (–43, –10) –26 (–43, –9) –26 (–43, –9) Other –13 (–40, 14) –50 (–79, –21) –40 (–70, –11) –49 (–77, –21) –49 (–77, –21) –39 (–67, –11) P-value heterog. (2 d.f.) 0.123 0.002 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 0 0 0 0 0 0 Other –77 (–92, –63) –72 (–88, –55) –75 (–92, –58) –67 (–83, –50) –80 (–98, –63) –94 (–112, –77) P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Open in new tab Table 5 The effect of maternal education, marital status and nationality on birthweight (g) of offspring by year: Estonia, 1992–1997 (singleton live births only) . 1992 β (95% CI)a . 1993 β (95% CI)a . 1994 β (95% CI)a . 1995 β (95% CI)a . 1996 β (95% CI)a . 1997 β (95% CI)a . a All regression coefficients are adjusted for the other two social variables in the Table, maternal age, parity, smoking, gestational age and sex of the infant. b Baseline category. Mother's education Basic or less –50 (–80, –21) –95 (–126, –64) –89 (–121, –56) –90 (–122, –58) –95 (–128, –62) –121 (–154, –87) Secondary –27 (–49, –6) –27 (–50, –4) –36 (–62, –11) –31 (–56, –6) –27 (–53, –1) –45 (–71, –19) Higher –18 (–40, 3) –14 (–38, 9) –28 (–53, –3) –24 (–49, 0) –16 (–42, 9) –32 (–58, –7) Universityb 0 0 0 0 0 0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 0 0 0 0 0 0 Cohabiting –16 (–31, 0) –13 (–29, 3) –32 (–49, –16) –27 (–43, –10) –26 (–43, –9) –26 (–43, –9) Other –13 (–40, 14) –50 (–79, –21) –40 (–70, –11) –49 (–77, –21) –49 (–77, –21) –39 (–67, –11) P-value heterog. (2 d.f.) 0.123 0.002 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 0 0 0 0 0 0 Other –77 (–92, –63) –72 (–88, –55) –75 (–92, –58) –67 (–83, –50) –80 (–98, –63) –94 (–112, –77) P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 . 1992 β (95% CI)a . 1993 β (95% CI)a . 1994 β (95% CI)a . 1995 β (95% CI)a . 1996 β (95% CI)a . 1997 β (95% CI)a . a All regression coefficients are adjusted for the other two social variables in the Table, maternal age, parity, smoking, gestational age and sex of the infant. b Baseline category. Mother's education Basic or less –50 (–80, –21) –95 (–126, –64) –89 (–121, –56) –90 (–122, –58) –95 (–128, –62) –121 (–154, –87) Secondary –27 (–49, –6) –27 (–50, –4) –36 (–62, –11) –31 (–56, –6) –27 (–53, –1) –45 (–71, –19) Higher –18 (–40, 3) –14 (–38, 9) –28 (–53, –3) –24 (–49, 0) –16 (–42, 9) –32 (–58, –7) Universityb 0 0 0 0 0 0 P-value trend (1d.f.) <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Mother's marital status Marriedb 0 0 0 0 0 0 Cohabiting –16 (–31, 0) –13 (–29, 3) –32 (–49, –16) –27 (–43, –10) –26 (–43, –9) –26 (–43, –9) Other –13 (–40, 14) –50 (–79, –21) –40 (–70, –11) –49 (–77, –21) –49 (–77, –21) –39 (–67, –11) P-value heterog. (2 d.f.) 0.123 0.002 <0.001 <0.001 <0.001 <0.001 Mother's nationality Estonianb 0 0 0 0 0 0 Other –77 (–92, –63) –72 (–88, –55) –75 (–92, –58) –67 (–83, –50) –80 (–98, –63) –94 (–112, –77) P-value <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 Open in new tab Figure 1 Open in new tabDownload slide Mean birthweight of singleton live births by maternal education, marital status and nationality: Estonia, 1992–1997 Figure 1 Open in new tabDownload slide Mean birthweight of singleton live births by maternal education, marital status and nationality: Estonia, 1992–1997 We thank the staff of the Estonian Medical Birth Registry who provided the data for this study. This study was supported by a grant from the UK Department for International Development and by the internal funds of the Institute of Experimental and Clinical Medicine in Tallinn. However, the Department for International Development can accept no responsibility for any information provided or views expressed. References 1 WHO. Health for All Data Base. Copenhagen: World Health Organization, 1998. 2 Shkolnikov VM, Leon DA, Adamets S, Andreev E, Deev A. Educational level and adult mortality in Russia: an analysis of routine data 1979 to 1994. Soc Sci Med 1998 ; 47: 357 –69. 3 Koupilova I, Bobak M, Holcik J, Pikhart H, Leon DA. Increasing social variation in birth outcomes in the Czech Republic after 1989. Am J Public Health 1998 ; 88: 1343 –47. 4 United Nations Children's Fund. Education for All. Economies in Transition Studies. Regional Monitoring Report No. 5. Florence: UNICEF, 1998. 5 WHO. International Statistical Classification of Diseases and Related Health Problems. Tenth Revision. Geneva: World Health Organization, 1993. 6 Berkowitz GS, Papiernik E. Epidemiology of preterm birth. Epidemiol Rev 1993 ; 15: 414 –43. 7 Stata Corporation. Stata Reference Manual: Release 5. Texas: College Station, 1997. 8 Karro H, Rahu M, Gornoi K, Baburin A. Estonian Medical Birth Registry 1992–1994: association of risk factors with perinatal mortality. Eur J Obstet Gynecol Reprod Biol 1998 ; 80: 151 –56. 9 Koupilova I, Vågerö D, Leon DA et al. Social determinants of size at birth in the Czech and Swedish populations, 1989–1991. Paediatr Perinat Epidemiol 1998 ; 12: 7 –24. 10 Evans S, Alberman E. International collaborative effort (ICE) on birthweight; plurality; and perinatal and infant mortality II: Comparisons between birthweight distributions of births in member countries from 1970 to 1984. Acta Obstet Gynecol Scand 1989 ; 68: 11 –7. 11 Alberman E. Are our babies becoming bigger? J R Soc Med 1991 ; 84: 257 –60. 12 Pudule I, Grinberga D, Kadziauskiene K et al. Patterns of smoking in the Baltic Republics. J Epidemiol Community Health 1999 ; 53: 277 –82. 13 Estonian Labor Force Surveys 1995 and 1997. Tallinn: Statistical Office of Estonia, 1998. 14 Dietz J, Grøgaard JB. Political attitudes. In: Grøgaard JB (ed.). Estonia in the Grip of Change: The NORBALT Living Conditions Project. Fafo Report 190. Oslo: Falch, 1996, pp.225–43. 15 UNDP. Estonian Human Development Report 1998. Tallinn, Estonia: United Nations Development Programme. 16 Statistics on birth in Estonia 1992–1996. Tallinn: Estonian Medical Statistics Bureau, Estonian Medical Birth Register, 1998. 17 Jacobsen B. Population. In: Grøgaard JB (ed.). Estonia in the Grip of Change: The NORBALT Living Conditions Project. Fafo Report 190. Oslo: Falch, 1996, pp.19–35. 18 Vågerö D, Koupilova I, Leon DA, Lithell UB. Social determinants of birthweight, ponderal index and gestational age—Sweden in the 1920s and the 1980s. Acta Paediatrica 1999 ; 88: 445 –53. 19 Sanjose S, Roman E, Beral V. Low birth weight and preterm delivery, Scotland, 1981–84: effect of parents' occupation. Lancet 1991 ; 338: 428 –31. 20 Arntzen A, Samuelsen SO, Magnus P, Bakketeig LS. Birth weight related to social indicators in Norway. Eur J Public Health 1994 ; 4: 92 –97. 21 Leon DA. Influence of birth weight on differences in infant mortality by social class and legitimacy. Br Med J 1991 ; 303: 964 –67. 22 Kaasik T, Andersson R, Hörte LG. The effects of political and economic transitions on health and safety in Estonia: an Estonia-Swedish comparative study. Soc Sci Med 1998 ; 47: 1589 –99. © International Epidemiological Association 2000
TI - Social determinants of birthweight and length of gestation in Estonia during the transition to democracy
JF - International Journal of Epidemiology
DO - 10.1093/ije/29.1.118
DA - 2000-04-01
UR - https://www.deepdyve.com/lp/oxford-university-press/social-determinants-of-birthweight-and-length-of-gestation-in-estonia-DPHEfBcd9j
SP - 118
VL - 29
IS - 1
DP - DeepDyve
ER -