Pregnancy and Heart Disease
It is known that high oestrogen levels during pregnancy cause permanent changes to the mother’s chromosomes, in a process known as epigenesis.
This was previously used as one of the reasons to explain why women who have multiple pregnancies are at greater risk of developing heart disease.
Recent studies (such as Peters et al. 2016), however, are beginning to demonstrate that the exact same relationship between family size and development of cardiac disease is seen in men. For both men and women, having one child seems somewhat protective against cardiac disease (that is to say that individuals with one child have a lower incidence of heart disease than those with none), but after this point, cardiac risk increases with increasing number of children.
The reasons for the relatively high incidence of heart disease in childless individuals is not discussed, and is likely to be complex. Whilst there are positive social impacts from having a child, presumably this is only applicable to those who wanted one in the first place! Those who make a conscious decision not to have children may invest more in relationships with other family members, friends, their partner or even pets, who presumably provide a similar level of social support. However, it is difficult to separate out the voluntarily from the involuntarily childless; the fertile from the infertile (some of whose infertility may be accompanied by comorbidities, or some of whom may not be able to have children due to long-term illness). An interesting further study would be to look at the difference between those who are childless by choice vrs those who are childless due to a medical condition.
A study of adoptive parents would be another interesting angle. If the same correlation between number of adoptive children and incidence of heart disease in the parents were observed, it would further demonstrate the non-biological link, although it could of course bring up more questions than answers, given that adoptive parents tend to be more educated and affluent than the general population.
Why did it take so long?
Since men were included in studies of family size and cardiac disease, the potential reasons – undoubtedly socioeconomic – behind the link between family size and cardiac disease seem obvious. It seems almost unbelievable that this link was not obvious to people before. One could, of course, write an entire essay on the historically blind acceptance of the “fact” that issues to do with childbirth, children and family size were exclusively part of the female sphere. We can thank feminism for the increasing visibility and inclusion of men in the discussion, who have historically been ignored from discussion of children and family.
But it cannot be denied that there is are some genuine correlations between pregnancy and cardiovascular disease, but not necessarily causative. It may be that pregnancy may unmask rather than cause vulnerability in the maternal cardiovascular system (Peters & Regitz-Zagrosek, 2016). Cardiac arrhythmias (palpitations, which can be captured on handheld ECG monitors) and shortness of breath during pregnancy, though usually benign, are common reasons for referral for electrocardiology (ECG) and echocardiography in the UK. Some diseases not so obviously cardiac can have cardiac ramifications further down the line. Gestational diabetes associated with a seven-fold higher risk of diabetes later in life, and pre-eclampsia associated with a doubled risk of cardiovascular events.
Unfortunately, women with pregnancy complications are not currently monitored after pregnancy (only if and when they have another pregnancy), so the opportunity to take preventative and protective measures against the future development of disease is missed. It makes sense, therefore, for women to take this matter own hands and monitor their health both during and after pregnancy, particularly if they experienced any of the aforementioned conditions during gestation.
References
Peters, S., Yang, L., Guo., et al. (2016). Parenthood and the risk of cardiovascular diseases among 0.5 million men and women: findings from the China Kadoorie Biobank. International journal of epidemiology 2016.
Peters, S. & Regitz-Zagrosek, V. (2017). https://academic.oup.com/eurheartj/article/38/19/1448/3823351/Pregnancy-and-risk-of-cardiovascular-disease-is