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Objective To examine whether women who develop coronary heart disease have different patterns of fetal and childhood growth from men in the same cohort who develop the disease.
Design Follow up study of women whose body size at birth was recorded and who had an average of 10 measurements of height and weight during childhood.
Setting Helsinki, Finland.
Subjects 3447 women who were born in Helsinki University Central Hospital during 1924-33 and who went to school in Helsinki.
Main outcome measures Hazard ratios for hospital admission for or death from coronary heart disease. Results Coronary heart disease among women was associated with low birth weight (P = 0.08 after adjustment for gestation, P = 0.007 after adjustment for placental weight) and was more strongly associated with short body length at birth (P = 0.001 and P [is less than] 0.0001, respectively). The hazard ratio for women developing coronary heart disease increased by 10.2% (95% confidence interval 4.3 to 15.7) for each cm decrease in length at birth. The effect of short length at birth was greatest in women whose height "caught up" after birth so that as girls they were tall. Such girls tended to have tall mothers. In contrast, men in the same cohort who developed the disease were thin at birth rather than short, showed "catch up" growth in weight rather than height, and their mothers tended to be overweight rather than tall.
Conclusion Coronary heart disease among both women and men reflects poor prenatal nutrition and consequent small body size at birth combined with improved postnatal nutrition and "catch up" growth in childhood. The disease is associated with reductions in those aspects of body proportions at birth that distinguish the two sexes--short body length in women and thinness in men.
In both men and women the development of coronary heart disease has been shown to be associated with low birth weight in relation to the length of gestation.[1-3] An interpretation of this is that coronary heart disease originates through adaptations that the fetus makes when it is undernourished. These adaptations include alterations in metabolism, hormonal output, and the distribution of cardiac output, and they may be combined with slowing of growth. Birth weight is a crude marker of fetal growth, as the same birth weight may be the outcome of many different paths of growth. Insights into the fetal adaptations that lead to coronary heart disease have come from studying body proportions at birth. Thinness at birth and shortness at birth--outcomes of different paths of reduced fetal growth--have been found to be associated with different biological risk factors for coronary heart disease. Placental weight has also been found to be an independent predictor of coronary heart disease in some studies.[7 8]
We have previously described death rates from coronary heart disease among a group of men who were born in Helsinki during 1924-33.[8 9] Their body size at birth was recorded in detail. As expected coronary heart disease was associated with low birth weight, after adjustment for gestation, but was more strongly associated with thinness at birth, measured by a low ponderal index (birth weight/length). The growth of these men through childhood and their living conditions were also recorded. This allowed us to examine for the first time the association between childhood growth and death from coronary heart disease, taking into account size at birth. We found that the highest death rates from coronary heart disease occurred in boys who were thin at birth but whose weight caught up so that they had an above average body mass from the age of 7 years.
We report here findings among the corresponding cohort of women born in the same hospital over the same period of time. The tempo of fetal and childhood growth differs in boys and girls.[10 11] Hence the paths of early growth that lead to coronary heart disease may differ in the two sexes.
We studied a sample of women who were born at the University Central Hospital during 1924-33 and who went to school in the city of Helsinki; 60% of all births in the city occurred in this hospital. Details of the birth records kept there have been previously described? Data on the mothers include age, parity, height, and date of last menstrual period, together with body weight measured on admission in labour. Data on their newborn babies include birth weight, length, head circumference, and placental weight. We studied women who were born at the hospital and who went to school in the city of Helsinki and were still resident in Finland in 1971. School health records for all children attending school in Helsinki are stored in the city archive. Details of these records have been described previously. They include an average of 10 (SD 4) measurements of length and weight between the ages of 6 and 16 years, recorded at periodic medical examinations. They also include the number of other people living in the child's home--recorded at the time of first examination--and the number of rooms. Since 1971 all residents of Finland have been assigned a unique personal identification number.
From the birth and school health records and identification numbers we identified 3688 women who fulfilled the criteria. Of these women, 241 subsequently emigrated, and the date of emigration was not always recorded. We therefore excluded them from the study to leave 3447.
By using the personal identification number we identified all hospital admissions …