Editor—Smith et al observe that adverse events in early life can be related to apparently disparate events later in life.1 For spontaneous pregnancy loss and subsequent ischaemic heart disease, they assume a role for inherited and acquired thrombophilias in the mother as a common aetiological factor.
They adjusted for the potential confounding effects of maternal age at the time of first birth, height, socioeconomic deprivation, essential hypertension, and complications during the first pregnancy. They were apparently not able to adjust for maternal body weight and thereby in conjunction with height, obesity. Maternal obesity is strongly associated with pregnancy loss, at least in subfertile women,2 and is an independent contributor to risk of ischaemic heart disease. Obesity may therefore be operating as a confounding factor in the association between pregnancy loss and subsequent heart disease.
The influence of obesity may also explain in large part the results of previous studies that have found an association between the total number of pregnancies and maternal risk of ischaemic heart disease. High parity is associated with adult weight gain.3 The confounding effect of obesity is also consistent with the null effect of therapeutic abortion on risk of ischaemic heart disease, as there is no particular reason for obesity to be strongly associated with receiving a termination.
The reported study had the strengths of prospective data collection, but it relied on data that were not collected for the purposes of the present analysis and may not contain details of all relevant confounding factors. Although the observation of Smith et al is important and multiple factors may be making a contribution, including inherited and acquired thrombophilias, we need further analysis on the effects of obesity and additional studies linking reproduction, adult weight gain, and increased risk of disease.4
Competing interests: None declared.
References
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