Maternal occupation and delivery outcome: a study using central registry data

Social inequality in fetal and perinatal mortality in the Nordic countries

Aim: The aim of this study is to review the epidemiological literature from the past 27 years on social inequality in fetal and perinatal mortality in the Nordic countries in order to examine whether social inequalities in fetal and perinatal mortality exist, and whether there are differences between the countries. Methods: The databases MEDLINE and EMBASE were searched for Nordic epidemiological studies published between January 1980 and August 2007 about the association between social indicators and the outcomes spontaneous abortion, stillbirth or perinatal mortality. Thirty-five studies that fulfilled the inclusion criteria were identified for this review. Results: Social differences in stillbirth and perinatal mortality were found in all of the identified Finnish and Norwegian studies and in the majority of studies from Denmark, whereas in the Swedish studies the findings were less consistent. As only a small number of studies on spontaneous abortion were identified (n=3), no conclusions were drawn with regard to this outcome. Conclusions: There seems to be a reasonable body of evidence that social inequality in stillbirth and perinatal mortality exists in Norway, Finland and Denmark, whereas the conclusions regarding Sweden are more uncertain. A number of methodological problems complicate the comparison of the findings. Nordic collaborative analyses of social gradients in spontaneous abortion, stillbirth and perinatal mortality, which take these methodological concerns into account, are needed in order to draw inferences across countries.

Maternal negative attitudes towards pregnancy as an independent risk factor for low birthweight

AIM

Recently, Japan has witnessed an increase in the number of low-birthweight (LBW) infants. LBW children face a variety of social and medical risk factors. Thus, besides reducing infant mortality, preventing LBW would have many other important health benefits. Emotional status during pregnancy is stated as one of the important risk factors for LBW. This study aims to clarify the relationship between maternal emotions and low birthweight (LBW) after adjusting the effects of other well-known factors that influence LBW.

METHODS

This community-based case-control study involved 145 newborns with LBW (cases) and 213 newborns with normal weight (controls). They were born in the municipalities that fall within the jurisdiction of the Yoshida public health center between 1st January 2003 and 30th September 2004. Participants' mothers were interviewed using a simple, structured questionnaire to collect general data on mother and infant, hazardous habits and maternal socioeconomic, occupational and psychological factors. The odds ratio with a 95% confidential interval of delivering LBW infants was calculated using logistic multivariable regression analysis based on maternal and infant factors.

RESULTS

In the multivariable regression model, the second-born or subsequent infant was unlikely to be LBW. On the contrary, maternal smoking habit during pregnancy, mothers who kept house by themselves and maternal negative attitudes towards pregnancy during the early stages promoted LBW incidence.

CONCLUSION

Maternal negative attitude towards pregnancy during the early stages was an independent LBW risk factor and our simple questionnaire can be used to estimate maternal psychological status in early pregnancy.

The use of national health registers for studying environmental causes of congenital defects

This review summarizes and discusses the use of central health registers in studies of causes of congenital malformations. The review is illustrated using data from the Swedish Medical Birth Register with adjacent registers and gives examples of different methods to identify environmental exposures. The review stresses the usefulness of this approach but also the inherent problems of which the researcher must be fully aware.

Impaired fasting glucose and impaired glucose tolerance are related to both heredity and low birth weight

AIM

The aim of the study was to test the hypothesis of an association between low birth weight (LBW), abnormal glucose metabolism and heredity.

METHODS

Common subjects were identified as newborns in a local birth register and as adult participants in the Västerbotten Intervention Programme (n=7796). Outcome measures such as impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) were investigated in relation to LBW, family history of diabetes, and sex.

RESULTS

Fasting plasma glucose and two-hour plasma glucose were elevated among women with LBW in relation to normal birth weight (NBW). Men and women with NBW had increased risks of IFG and IGT if there was a hereditary background of diabetes mellitus. LBW and hereditary background of diabetes mellitus interacted on the risk of IFG and IGT in women.

CONCLUSIONS

Hereditary background of diabetes and LBW increase the risk of abnormal glucose metabolism such as IFG and IGT in early middle age. LBW and hereditary background of diabetes have a synergy effect on the risk of IFG and IGT in women.

Fetal exposure, heredity and risk indicators for cardiovascular disease in a Swedish welfare cohort

BACKGROUND

The overall aim was to test whether low birthweight (LBW) in newborns is associated with the risk indicators for cardiovascular disease in early middle age, even in a welfare society. Further, a possible interaction of LBW and heredity for myocardial infarction or stroke was investigated.

METHODS

Overall, subjects were identified as newborns in a local birth register, and as adult participants, in the Västerbotten Intervention Program (n = 7876). Outcome measures such as systolic (SBP) and diastolic blood pressures (DBP), body mass index (BMI), cholesterol, triglycerides and anthropometrics were investigated (at age 29-41 years) in relation to LBW.

RESULTS

Low birthweight was associated with increased SBP and DBP. Triglycerides were elevated among women with LBW and total cholesterol was elevated in men with LBW. Heredity for myocardial infarction or stroke interacted with LBW, and indicated a synergistic effect on the level of SBP. The BMI did not differ between LBW and normal birthweight subjects.

CONCLUSIONS

Our interpretation is that the 'fetal origins' hypothesis' is valid for middle-age subjects who grow up in a welfare society. The population attributable proportions that result from different exposures to LBW were relatively small overall; from a public health perspective, heredity was more important than LBW for elevated SBP.

The effect of heavy maternal workload on fetal growth retardation and preterm delivery. A study among southern Thai women

Heavy maternal workloads are considered to be hazardous to the fetus. The effects of physical activity during pregnancy on low birth weight (LBW), small for gestational age (SGA), and prematurity were assessed from a sample of 1797 women in a follow-up study at the antenatal clinic of two hospitals in southern Thailand. The women were interviewed twice, at 17 and 32 gestational weeks. Outcome data were obtained from medical records and the newborn gestational age determined using Dubowitz's score. The risk of SGA was elevated for women working > 50 hours/week, squatting in work, commuting > 1 hour/day, and having high psychological job demands; the risk of preterm delivery was increased with obstetrical complications. Women who worked long hours and had demanding work conditions had an elevated risk of giving birth to SGA infants but not of preterm delivery.

Social class differences in health until the age of seven years among the Finnish 1987 birth cohort

Studies on social class differences in childhood health are controversial partly because of different data collection methods, limited sample sizes and the use of limited numbers of health indicators. The increasing collection of health register data enables the use of such data in social class studies. Our purpose was to investigate social class differences in mortality and morbidity among all children born in Finland in 1987 (N=59,865 liveborns) until the age of seven by using several national health registers, and to study whether perinatal health explains these differences. The follow-up was based on data linkage with six national health registers, with 18 regional registers of mentally disabled children, covering the whole country, and with 38 educational registers of the largest county. Morbidity was measured in terms of a cumulative disease index, the cumulative incidence of asthma, diabetes, epilepsy and intellectual disability, hospitalisations, disease-related welfare benefits and special education. Social class, divided in four groups (I-III, Others) was defined by using the mother's occupation at the time the child was seven years old. Our study showed that register-based data collection is a feasible method for studying social class differences in health. In the unadjusted analysis, social class differences were found for all indicators except mortality after the age of one year and for the cumulative incidence of asthma and diabetes. After adjusting for confounders, the children in the lowest social class had the highest risk for poor health outcome both in the perinatal period and in childhood, and had the most intellectual disabilities, the highest mean of hospitalisation days, and received the most special education. The differences were not explained by perinatal health. The health of the children in the lowest social class was poorer, especially regarding mental indicators.

Methods for the evaluation of social effects on birth weight-- experiences with Swedish population registries

All births in Sweden in 1986, registered in the Medical Birth Registry, were analyzed with linked data from the November 1985 census in order to identify variables which could be used as proxy variables for the socio-economic situation of the women, using birth weight as outcome variable. Two phenomena appear to be strong socio-economic indices of significance for birth weight: whether the woman co-habited or not at the census and whether she had a long education (> 14 years) and an "academic" work. The two variables interacted, however: when the woman had a long education, cohabitation status played no significant role. Maternal education as judged from occupation seemed to play a more important role than paternal education or job. To some extent, the effects of the socio-economic variables could be explained by different smoking habits but a residual effect existed which may have different explanations. Cohabitation status and education may be used as estimates of socio-economic level of significance for birth weight and perhaps other pregnancy outcome in the analysis of, for instance, the effect of various occupational exposures on pregnancy outcome.

Maternal occupation and congenital heart defects: a case-control study

This paper reports a Swedish analysis of the possible effect of maternal occupation on the occurrence of congenital heart defects. The analysis included 3324 infants (1108 cases and 2216 controls) born during the period 1982-1986. Information on maternal occupation was retrieved using two sources: the 1985 census and the Medical Birth Registry. A comparison between these two sources using the information on mothers of 756 infants born in 1986 showed a good concordance although 11% of the women were reported with a different employment status. No association appeared between the type of maternal occupation and the occurrence of infant congenital heart defects although some odds ratios were slightly above 1.

High blood pressure during pregnancy and working conditions among hospital personnel

The relationship between working conditions and high blood pressure during pregnancy was analysed in a sample of 621 women hospital employees in the Paris region over the period 1979-1981. Data were collected by interviews during the routine medical visit at the end of postnatal leave. Women who had to work standing up for extended periods of time, who had to carry heavy loads or who had to perform heavy cleaning tasks had high blood pressure during their pregnancy more often than women not exposed to these working conditions. The accumulation of two out of the three or these three working conditions by the same woman was strongly related to high blood pressure. This relation remained significant when other risk factors of hypertension, such as age, parity, corpulence and tobacco use, were taken into account in a multiple logistic regression.

Is preterm delivery still related to physical working conditions in pregnancy?

STUDY OBJECTIVE

The aim was to determine the relationship between working conditions during pregnancy, women's occupation, and preterm birth.

DESIGN

This was a retrospective survey.

SETTING

The study was carried out in four public maternity units in France in 1987 and 1988.

SUBJECTS

1949 women were interviewed after the delivery during their stay in hospital. Of these, 1002 held a job during pregnancy, but this report is confined to 875 women who had a single live birth and who had worked for more than the first trimester of pregnancy.

MEASUREMENTS AND MAIN RESULTS

Information about social and occupational status was obtained through interviews, and data about gestational length were obtained from medical records. The primary results showed that preterm birth did not vary significantly according to working conditions whereas it differed according to occupational group.

CONCLUSIONS

Occupation, but not working conditions, affected the incidence of preterm birth. This result is discordant with other studies which underlined the excess of preterm births among women with strenuous working conditions. Reasons for this discrepancy may include (1) change in perception of "strenuous working conditions"; (2) improved working conditions; (3) the development of "preventive" strategies by pregnant women. Occupation is a more reliable indicator of risk than self described working conditions.