Number of children and coronary heart disease risk factors in men and women from a British birth cohort

objective To examine the association between number of children and coronary heart disease (CHD) risk factors in women and men. Design Prospective cohort study. Setting Britain. Sample A total of 2977 individuals (51% women) from the Medical Research Council National Survey of Health and Development, a birth cohort study of individuals born in Britain in 1946 and followed up regularly throughout life. Main outcome measures Blood pressure, body mass index (BMI), waist to hip ratio (WHR), total, high-density lipoprotein and low-density lipoprotein cholesterol and triglyceride levels, and glycated haemoglobin (Hb(A1C)) measured at age of 53 years. Results Number of children showed no consistent relationship with CHD risk factors at age 53 years in either men or women, and no obvious and consistent sex differences were observed. Mean BMI (95% CI) increased with increasing numbers of children (P = 0.01) in women from 27.4 kg/m(2) (26.6-28.2) in those with one child to 28.6 kg/m(2) (27.6-29.6) in those with four or more children. WHR and type II diabetes in women and Hb(A1C) in men were the only other risk factors exhibiting a linearly increasing trend with increasing number of children. These associations were largely explained by adjustment for behavioural and lifestyle variables. Conclusion Our findings suggest that any association between number of children and CHD risk factors is a result of lifestyle and behaviours associated with family life rather than being as result of the biological impact of pregnancy in women.