In general, in both the UK based and all of the Brazil based birth cohorts, mothers and infants from poorer and less-educated backgrounds had more adverse health outcomes than those from richer and better-educated background. The magnitudes of income and education-related inequalities were outcome and setting specific and were assessed using the RII—a ratio-type measure. Stronger income-related inequalities for smoking and education-related inequalities for breast feeding were observed in the ALSPAC than in the Pelotas cohorts. However, stronger income and education-related inequalities in caesarean section and higher education-related inequalities in preterm birth were observed in the Pelotas cohorts than in the ALSPAC study. Education-related inequalities became wider over time (ie, stronger in more contemporary birth cohorts) in the Pelotas cohorts for smoking, preterm birth and breast feeding.
The main strengths of the study derived from the use of prospective information obtained among large unselected populations with a high response rate and the availability of comparable variables between ALSPAC and the Pelotas cohort studies. However, some methodological difficulties need to be discussed. First, SEP is a complex phenomenon and different indicators have been described to capture its dimensions. Education and occupation, household income and household conditions are frequently used SEP indicators, each reflecting somewhat different individual and societal forces associated with health and disease. In our study, only maternal education and family income were available both in the ALSPAC and the Pelotas cohort studies databases, and it was not possible to examine the role of other SEP indicators. Second, maternal education in the Pelotas studies was measured as complete years of schooling while in the ALSPAC study it was measured as educational achievement. Schooling and educational achievement do not mean exactly the same thing. It is possible that stronger education-related inequalities would exist between women who do and do not have higher qualifications. Third, the meaning of family income may vary between settings and may be influenced by family size, but information on the latter was not collected in the perinatal interview for the 1982 Pelotas cohort. Finally, although the proportion of missing values in family income in the ALSPAC database was relatively high, the use of multiple imputation analysis to assess the impact of missing values resulted in effect estimates that were essentially the same as those without imputation, which provides some assurance against substantial selection bias.20
We found higher income-related inequalities for smoking during pregnancy in the ALSPAC than in the Pelotas cohort studies. The disadvantages of being poor in a rich and prosperous country compared to being in the same condition in a low or middle-income country have been raised before.21
In the Pelotas studies, even though prevalence rates of smoking during pregnancy have declined, inequalities in education-related inequalities are increasing, showing that tobacco control policies and programmes have been reaching the better-educated in a more effective way than the less-educated pregnant women during the last decades.
Patterns of professional attendance at birth varied in the two countries. While midwives deliver over 75% of UK newborns, in southern Brazil virtually all deliveries are carried out by obstetricians.22
This is why deliveries not attended by a doctor are more frequent in the ALSPAC than in Pelotas. Several studies have documented large differences in the use of delivery care according to women's wealth and/or educational levels.23 24
In ALSPAC, while low income-related inequalities were found for deliveries not attended by a doctor, education-related inequalities were as high as in the 2004 Pelotas cohort study. Among the Pelotas studies, the largest income-related inequalities were found in the 1982 cohort. Health services could have been inaccessible or unaffordable to women with few economic resources in 1982. The substantial expansion of healthcare services during the early 1990s, as well as an increase in the availability of trained professionals, could explain why trends in both income and education-related inequalities decreased in Pelotas cohort studies throughout the last decades.
Despite continuing debate on the appropriate level of population-based caesarean rates, rates of no less than 5% and no more than 15% have been recommended.25
In the ALSPAC study, the prevalence of caesarean sections was below the recommended upper limit25
and no educational-related inequalities were found. In the Pelotas studies, rates of caesarean section were high both in the public and private sector. For private patients, the current rate in Pelotas is at the striking level of 82%.26
These differences likely reflect the fact that obstetricians carry out most deliveries in Pelotas, whereas midwives do so in the UK. Higher caesarean sections rates do not mean better quality healthcare and, paradoxically, at least in terms of caesarean section rates, the Latin-American poor may be receiving healthcare of better quality than the rich.27
However, targets for this indicator should be determined to assure that those most in need are served and that overuse without health need is actively discouraged.
Poor intrauterine growth and preterm birth are not only predictors for perinatal and neonatal mortality and morbidity but also determine human susceptibility to disease and quality of life later on.28
The risk of delivering an IUGR infant was higher among poor and less-educated women, as has been described in previous studies,29 30
and the magnitude of income and education-inequalities was similar in the ALSPAC and the Pelotas studies. Rates of preterm births, which were almost the same in the ALSPAC and the 1982 Pelotas study, increased in the Pelotas cohorts nearly three-times during the studied period— a finding that was reported in a previous publication.26
Neither income nor education-related inequalities were observed in the 1982 Pelotas cohort. In the 2004 Pelotas cohort, education-related inequalities in preterm birth become more evident and higher than in the ALSPAC study even after adjustment for maternal and newborn characteristics. These findings are in accordance with other investigations that showed the importance of maternal educational level among other SEP measures as a strong predictor of inequalities in preterm birth.31
Breast feeding is the best way of feeding an infant and provides well-known benefits to the infant and the mother.32 33
Income-related inequalities in breast feeding were observed in the ALSPAC study but not in the 1982 and 1993 Pelotas cohort studies. High education-related inequalities were found in the ALSPAC study, with magnitudes almost three-times higher than in the 2004 Pelotas cohort study. Our findings are consistent with previously reported observations of substantial inequalities in breast feeding practices within UK.34 35
Brazil has, for more than 20 y, implemented several strategies to promote breast feeding36 37
and, specifically, the city of Pelotas was a participating centre in the Multicenter Growth Reference Study (MGRS) where a breast feeding support programme was implemented from 1997–1998. After the MGRS, several interventions promoting breast feeding continued to be carried out in the city, which may underlie increasing trends in breast feeding in the last decades.38
However, breast feeding interventions and programmes seemed to have better-reached women with higher schooling, widening the gap between women at the bottom and at the top of the educational hierarchy.
Finally, it should be noted that whereas income and education-related inequalities were evident in both populations, the poorest in the UK were in a better situation than those in Pelotas for all studied health indicators with the exception of breast feeding duration.