Prenatal nutrition and birth weight: experiments and quasi-experiments in the past decade.
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Biomedical subjects
Publications and source records attributed to M Susser.
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We compared cigarette smoking during pregnancy among 574 women who aborted spontaneously (cases) and 320 women with delivery after at least 28 weeks' gestation (controls). Log-linear analysis was used to test the hypothesis that smoking is associated with spontaneous abortion. Several potentially confounding variables--namely, age at last menstrual period and the number of previous pregnancies ending in spontaneous abortion, in induced abortion and in live birth--were controlled in the analysis. Women who had aborted spontaneously reported smoking during pregnancy more often than those with delivery after 28 weeks' gestation: 41% of cases and 28% of controls smoked. The odds ratio for the highly significant association with smoking was 1.8. The association did not vary with age or previous obstetric events. We conclude that smoking during pregnancy is a risk factor for spontaneous abortion.
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The prevalence of severe mental retardation, derived from military records, is analyzed in terms of time trend, region, religious affiliation and urbanization of birth place. The data are singular in that they are national and virtually complete for a total population of young men, 19-year-old survivors of male births in the Netherlands over the years 1944 through 1947, and they include variables not previously studied. Previous local studies are shown to agree well with the national prevalence of 3.7 per 1,000. Prevalence rose through the four birth years for all forms of severe mental retardation, but most markedly for Down's syndrome. In this condition agency surveys usually yeild equivalent rates to population surveys, and are an economical means of monitoring prevalence. Differences in rates are quite likely to indicate substantive differences. The remarkable similarities in rates from past surveys may reflect a high proportion of chromosomal and genetic abnormalities. The divergence between urban and rural rates over time demonstrated in this paper for four annual cohorts is attributed by inference to disparate increases in survival in different ecologic settings.
The prevalence of mild mental retardation in 19-year-old survivors of male births during 1944-1947 is derived from military records. The data are singular in that they are national, virtually complete for a total population of more than 400,000 men and include attributes not previously examined. They allow for the simultaneous use of three criteria: education (history of special schooling), psychometric (Raven intelligence test score), and clinical diagnosis (ICD (1948) 325.2, 325.3), which yielded rates per 1000 of 30,58 and 61, respectively. Rates by all three criteria varied in similar fashion with father's occupation and with religious affiliation. Rates by the psychometric and diagnostic criteria were higher for rural- and urban-born, while rates by the special schooling criterion were lower for rural-born. These variations are presumed to indicate deficiencies in rural provisions of special schooling on the one hand, and a substantive increment in "true" prevalence on the other. Marked variations in rates by province are not accounted for by social class and urban/rural birthplace. A rise in rates in the 1947 birth cohort on the psychometric and diagnostic criteria but not on the schooling criterion is attributable to a scoring change in the IQ criterion. Relative risks are estimated for the psychometric criterion of low Raven test score according to father's occupation, urban-rural origin, and religious affiliation. The overlap of identification among individuals designated by one, two, or three of the criteria is examined, and the issue of labeling is explored.
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To make sound inferences about the distribution, causes and risks of congenital anomalies requires an understanding of selective survival among fetuses. Studies of spontaneous abortions are therefore advocated. A simple model is proposed of the distribution, among spontaneous abortions and births, of conceptuses with and without anomalies. The resulting equation accomodates both maternal and fetal factors. Interaction between maternal and fetal factors is hypothesized, in the form of a maternal device for screening out anomalous conceptuses. A number of the known facts about congenital anomalies are shown to be plausibly interpreted in terms of the proposed model. Finally, some clinical and epidemiologic implications of the model for the study of spontaneous abortions are pointed out.
Prenatal exposure to the Dutch famine of 1944-1945 reduced postpartum maternal weight, birth weight, placental weight, length at birth, and head circumference at birth. These conclusions are based on maternities occurring in the famine area and exposed to famine during some part of gestation as compared both with maternities in nonfamine areas, and with maternities before and after the famine. Third trimester exposure accounted for the whole of the famine effects. Length of gestation was not affected by third trimester exposure, and did not mediate the effects on infant exposure, and did not mediate the effects on infant dimensions at birth. Effects were apparent only below a threshold value of official food rations of 1,500 cal daily average during the third trimester. (Calorie value for official food rations can be assumed to be lower than actual food intake.) Maternal weight declined 4.3% during the famine and rose 10.5% after the famine. Birth weight declined 9% during the famine, and rose 9% after the famine. Placental weight declined 15% during the famine, and rose 14% after the famine. Length at birth declined 2.5% during the famine, and rose 1.5% after the famine. Head circumference declined 2.7% during the famine, and rose 2.4% afterward.
Effects of maternal exposure to famine during the prenatal period were compared among six indices of reproduction by the use of Z scores. Maternal weight was affected soonest, then birthweight and placental weight. Length and head size at birth were affected relatively less and only after exposure to more severe nutritional deprivation. Path models were constructed of the interrelations of caloric rations, length of gestation, maternal weight, and fetal dimensions. Above a threshold value of 1,5000 Cal dialy average official food rations available to mothers in the third trimester, a model in whichthe placenta is treated as a fetal dimension (or organ) seemed most appropriate. Below the threshold value, a model in which the placenta is treated as a transmitter of nutrients seemed most appropirate.
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